VDE-AR-N 4105:2011-08 Power generation systems connected to the low-voltage distribution network English translation of the VDE application rule VDE-AR-N 4105 Note: In case of doubt the German version will be valid.
Technical minimum requirements for the connection to and parallel operation with low-voltage distribution networks
English translation
VDE-AR-N 4105:2011-08 Power generation systems connected to the low-voltage distribution network — Technical minimum requirements for the connection to and parallel operation with low-voltage distribution networks
Contents Page Foreword.............................................................................................................................................................6 Introduction .........................................................................................................................................................6 1
Scope .....................................................................................................................................................6
2
Normative references.............................................................................................................................7
3
Terms, definitions and abbreviations .....................................................................................................8
3.1
Terms and definitions.............................................................................................................................8
3.2
Abbreviations........................................................................................................................................14
4
General framework conditions .............................................................................................................15
4.1
Provisions and regulations ...................................................................................................................15
4.2
Application procedure and connection relevant documents ................................................................15
4.3
Initial start-up of the power generation system ....................................................................................15
5
Network connection..............................................................................................................................16
5.1
Principles for determination of the network connection point ..............................................................16
5.2
Rating of the network equipment .........................................................................................................17
5.3
Permissible voltage change .................................................................................................................17
5.4
System reactions..................................................................................................................................18
5.4.1
General..............................................................................................................................................18
5.4.2
Rapid voltage changes......................................................................................................................18
5.4.3
Flicker................................................................................................................................................18
5.4.4
Harmonics and inter-harmonics ........................................................................................................19
5.4.5
Voltage unbalance ............................................................................................................................20
5.46
Commutation notches .......................................................................................................................20
5.4.7
Audio-frequency centralised ripple-control........................................................................................20
5.4.8
Carrier frequent usage of the customer network...............................................................................21
5.4.9
Precautionary measures against voltage drops and voltage interruptions .......................................21
5.5
Connection criteria ...............................................................................................................................21
5.6
Three-phase network ...........................................................................................................................22
5.6.1
General..............................................................................................................................................22
5.6.2
Three-phase synchronous generators ..............................................................................................22
5.6.3
Three-phase inverter systems...........................................................................................................23
5.7
Behaviour of the power generation system at the network..................................................................23
VDE-AR-N 4105:2011 (E)
5.7.1
Page General............................................................................................................................................. 23
5.7.2
Maximum permissible short-circuit current....................................................................................... 24
5.7.3
Active power output.......................................................................................................................... 24
5.7.3.1
Basics .......................................................................................................................................... 24
5.7.3.2
Generation management/network security management ........................................................... 24
5.7.3.3
Active power feed-in at overfrequency........................................................................................ 25
5.7.3.4
Active power feed-in at underfrequency...................................................................................... 26
5.7.4
Principles for network support .......................................................................................................... 26
5.7.5
Reactive power................................................................................................................................. 26
6
Construction of the power generation system/network and system protection (NS protection) ......... 29
6.1
General requirements.......................................................................................................................... 29
6.2
Central NS protection .......................................................................................................................... 29
6.3
Integrated NS protection...................................................................................................................... 30
6.4
Interface switch.................................................................................................................................... 30
6.4.1
General............................................................................................................................................. 30
6.4.2
Central interface switch .................................................................................................................... 30
6.4.3
Integrated interface switch ............................................................................................................... 31
6.5
Protective devices for the interface switch .......................................................................................... 31
6.5.1
General............................................................................................................................................. 31
6.5.2
Protective functions .......................................................................................................................... 32
6.5.3
Islanding detection ........................................................................................................................... 33
7
Metering for billing purposes ............................................................................................................... 34
8
Operation of the system ...................................................................................................................... 35
8.1
General ................................................................................................................................................ 35
8.2
Particular characteristics of the management of the network operator’s network............................... 36
8.3
Connection conditions and synchronisation ........................................................................................ 37
8.3.1
General............................................................................................................................................. 37
8.3.2
Connection of synchronous generators ........................................................................................... 38
8.3.3
Connection of asynchronous generators ......................................................................................... 38
8.3.4
Connection of power generation units with inverters ....................................................................... 38
8.4
Reactive power compensation ............................................................................................................ 38
9
Verification of the electrical properties ................................................................................................ 38
9.1
General ................................................................................................................................................ 38
9.2
Verification of the feed-in power.......................................................................................................... 39
9.2.1
Verification of the feed-in active power ............................................................................................ 39
9.2.2
Verification of the reactive power values.......................................................................................... 39
9.2.3
Verification of the reactive power transition function........................................................................ 39
9.3
Verification of the network reactions ................................................................................................... 39
9.4
Verification of the features of the network and system protection ...................................................... 39
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Page Annex A (informative) Explanations ................................................................................................................40 A.1
“Power generation system” (3.1.8) and “power generation unit” (3.1.9) ..............................................40
A.2
Permissible voltage change (5.3).........................................................................................................40
A.3
System reactions (5.4) .........................................................................................................................41
A.3.1
Rapid voltage changes.........................................................................................................................41
A.3.2
Flicker...................................................................................................................................................42
A.3.3
Harmonics and inter-harmonics ...........................................................................................................42
A.3.3.1
General..............................................................................................................................................42
A.3.3.2
Line-commutated inverters (six- or 12-pulse) ...................................................................................43
A.3.3.3
Pulse-modulated inverters ................................................................................................................43
A.4
Connection criteria (5.5).......................................................................................................................43
A.5
Reactive power (5.7.5) .........................................................................................................................44
A.6
General requirements, single-fault tolerance (6.1)...............................................................................46
A.7
Interface switch (6.4)............................................................................................................................47
A.8
Protective devices for the interface switch (6.5) ..................................................................................47
A.8.1
General.................................................................................................................................................47
A.8.2
Protective functions ..............................................................................................................................47
Annex B (informative) Connection examples ..................................................................................................48 B.1
Maximum apparent connection power SAmax ≤ 4,6 kVA ......................................................................48
B.2
Maximum apparent connection power SAmax ≤ 13,8 kVA ....................................................................49
B.3
Power generation system with communicative coupling of the single-phase inverters and with integrated NS protection ...............................................................................................................50
B.4
Maximum apparent connection power of SAmax > 30 kVA ...................................................................51
B.5
New power generation unit connected in parallel to an existing system SAmax > 30 kVA ...................52
B.6
Connection with meter column.............................................................................................................53
B.7
Connection for excess feed-in (self consumption in accordance with EEG, § 33 EEG and KWK-G, § 4 (3)) ....................................................................................................................................54
B.8
Connection for excess feed-in of > 30 kVA ..........................................................................................55
Annex C (informative) Examples of meter panel configurations .....................................................................56 C.1
Meter panel for connection of a power generation system with a maximum apparent connection power SAmax ≤ 30 kVA (full feed-in) ...................................................................................56
C.2
Meter panel for the connection of a power generation system with a maximum apparent connection power SAmax > 30 kVA and with central NS protection......................................................57
C.3
Meter panel for the connection of a power generation system that includes transformer measurement .......................................................................................................................................58
C.4
Meter panel (that may also be arranged in a decentralised manner) for the connection of a power generation system for self consumption or excess feed-in in accordance with EEG, § 33 and KWK-G, § 4............................................................................................................................59
C.4.1
General.................................................................................................................................................59
C.4.2
Schematic representation ....................................................................................................................60
C.4.3
Organisation of a central meter panel ..................................................................................................60 3
VDE-AR-N 4105:2011 (E)
Page Annex D (normative) Islanding detection........................................................................................................ 62 D.1
Islanding detection by means of the oscillating circuit test.................................................................. 62
D.2
Islanding detection by three-phase voltage monitoring....................................................................... 63
Annex E (informative) Examples for the connection evaluation of power generation systems...................... 64 E.1
Connection of a 20 kW photovoltaic system ....................................................................................... 64
E.2
Reactive power control of a heat led CHP .......................................................................................... 69
Annex F (normative) Forms (mandatory) ....................................................................................................... 71 F.1
initial start-up protocol for power generation systems......................................................................... 71
F.2
Data sheet for power generation systems........................................................................................... 72
F.3
Requirements for the test report for power generation units............................................................... 73
F.4
Requirements for the test report for the NS protection ....................................................................... 74
Annex G (informative) Forms (optional).......................................................................................................... 75 G.1
Application ........................................................................................................................................... 75
G.2
Certificate of conformity for power generation units............................................................................ 76
G.3
Certificate of conformity of the network and system protection........................................................... 77
Bibliography ..................................................................................................................................................... 78
Figure 1 — Synchronous generated voltage of a synchronous generator as an ideal balanced threephase system ...................................................................................................................................... 23 Figure 2 — Equivalent circuit diagram of a synchronous generator for the case of a short circuit ................. 23 Figure 3 — Active power reduction at overfrequency...................................................................................... 25 Figure 4 — Limit power range for the reactive power of a power generation system within the range of 3,68 kVA < SEmax ≤ 13,8 kVA (load-reference arrow system) ................................................... 27
∑
Figure 5 — Limit power range for the reactive power of a power generation system within the range of SEmax > 13,8 kVA (load-reference arrow system)...................................................................... 27
∑
Figure 6 — Standard characteristic curve for cos ϕ (P) ................................................................................... 28 Figure A.1 — Overview on the concepts of power generation unit and power generation system................. 40 Figure A.2 — Potential for optimisation provided by a suitable reactive power feed-in for typical overhead line or cable types (related to an operation mode where cos ϕ = 1) .................................... 44 Figure A.3 — Examples of a characteristic curve cos ϕ (P) with three nodes ................................................. 45 Figure B.1 — Connection of a single-phase power generation unit with full feed-in and a maximum apparent connection power ≤ 4,6 kVA................................................................................................. 48 Figure B.2 — Connection of 3 single-phase power generation units with full feed-in and a maximum apparent connection power ≤ 4,6 kVA per line conductor ................................................................... 49 Figure B.3 — Connection of 3 single-phase power generation units in full feed-in and with communicative coupling ...................................................................................................................... 50 Figure B.4 — Connection of 3 three-phase power generation units with full feed-in ...................................... 51 Figure B.5 — Connection of a new power generation unit connected in parallel to an existing system with full feed-in for a maximum apparent connection power SAmax > 30 kVA......................... 52
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Figure B.6 — Connection of a power generation system with meter column for a maximum apparent connection power SAmax > 30 kVA .......................................................................................................53 Figure B.7 — Connection of a power generation system with excess feed-in (taking into account self consumption in accordance with EEG, § 33 and KWK-G, § 4 (3)) .......................................................54 Figure B.8 — Connection of a power generation system with excess feed-in for a maximum connection power SAmax > 30 kVA .....................................................................................................55 Figure C.1 — TAB meter panel: general system and power generation system ≤ 30 kVA..............................56 Figure C.2 — TAB meter cabinet: general system and power generation system > 30 kVA...........................57 Figure C.3 — Meter panel for the connection of a power generation system that includes transformer measurement....................................................................................................................58 Figure C.4 — Meter panel (that may also be arranged in a decentralised manner) for the connection of a power generation system for self consumption or excess feed-in ................................................59 Figure C.5 — Measuring principle for the implementation of EEG 2009, § 33 (2) or KWK-G 2009, § 4 (3a) ..........................................................................................................................60 Figure C.6 — Connection variant for a central conventional meter panel with three-point fastening ..............60 Figure C.7 — Connection variant for a central eHZ meter panel with BKE-I ...................................................61 Figure D.1 — Example with integrated NS protection in the inverter...............................................................62 Figure E.1 — Power generation unit (sketch of the set-up and connections)..................................................64 Figure E.2 — Network (sketch) ........................................................................................................................64 Figure E.3 — Reactive power control of a heat led CHP .................................................................................69 Figure E.4 — Characteristic curve cos ϕ (P) of the CHP ..................................................................................69 Figure E.6 — Resultant characteristic curve Q(P)............................................................................................69 Figure E.6 — Characteristic curve cos ϕ (P) of the CHP ..................................................................................70 Figure E.7 — Resultant characteristic curve Q(P)............................................................................................70 Figure E.8 — Voltage deviation at the connection point ..................................................................................70 Figure E.9 — Loss parameter current square ..................................................................................................70
Table 1 — Permissible harmonic currents related to the network short-circuit power SkV that may be supplied in a network connection point ................................................................................................19 Table 2 — Setting values for the NS protection ...............................................................................................33 Table A.1 — Implementation of the connection criteria after 5.5 .....................................................................44 Table E.1 — Voltage change at the individual PCCs.......................................................................................66 Table E.2 — Voltage change at the individual PCCs (with the characteristic cos ϕ (P)) ..................................67
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Foreword This VDE application guide has been prepared under the responsibility of the Forum Network Technology/Network Operation within VDE (FNN). It has been prepared by the project group „Erzeugungsanlagen am Niederspannungsnetz“ (Power generation systems connected to the low-voltage distribution network) founded by the FNN steering committee “Low and medium voltage.” This VDE application guide was subject to public opposition proceedings.
Introduction The VDE application guide summarizes the essential aspects which have to be taken into consideration for the connection of power generation systems (translator’s note: the German term “Anlage” includes systems as well as installations and plants) to the network operator’s low-voltage network. It serves as a basis for both the network operator and the installer in the planning and decision-making process. In addition, the operator is given important information regarding the operation of such systems. This VDE application guide replaces the 4th edition of the VDEW guideline on “Generating Plants Connected to the Low-Voltage Network” („Eigenerzeugungsanlagen am Niederspannungsnetz“) [1] which has been fully redesigned and restructured to be more logical. Similar to the higher voltage levels, power generation systems supplying low-voltage networks will have to make a contribution to the static voltage stability in the future. Therefore, they have to contribute to the voltage stability in the low-voltage network during normal network operation. This has immediate effect on the systems’ design. This VDE application guide summarizes the essential aspects that have to be taken into consideration for the connection to the low-voltage network so as to maintain the safety and reliability of network operation in accordance with the provisions of the Energy Industry Act in the light of a growing share of decentralised power generation systems and to enable the limit values of voltage quality specified in DIN EN 50160 to be observed. Additional information is given for individual aspects to explain certain provisions of the VDE application guide. In order to reduce this VDE application guide to the most important elements, this explanatory information is summarized in Annex A in correspondence to the respective clauses. The calculation examples listed in Annex E allow for the permissibility of the connection of a power generation system to the low-voltage network to be checked based on the given data. If, in that context, connection to the low-voltage network is shown to be impossible, then connection to the higher voltage level, i.e. the medium-voltage network, may generally be considered. The connection evaluation required for this shall be carried out in accordance with the BDEW guideline “Generating Plants Connected to the Medium-Voltage Network” („Erzeugungsanlagen am Mittelspannungsnetz“) [2]. The Annexes F and G contain forms for the compilation of the required data of a power generation system from planning the network connection to the initial start-up of the power generation system. This VDE application guide is an integral part of the VDN guideline „Technische Anschlussbedingungen für den Anschluss an das Niederspannungsnetz“ (Technical connection conditions for connections to the lowvoltage network; TAB 2007) [3].
1
Scope
This VDE application guide applies to the planning, erection, operation and modification of power generation systems that are connected to a network operator’s low-voltage network and operated in parallel with this network (network connection point in the low-voltage network). In this context, in particular those modifications to power generation systems have to be taken into account, which have significant influence on the electrical behaviour at the network connection.
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VDE-AR-N 4105:2011 (E)
For the planning of a network connection as well as for the reconstructed and extended part of a power generation system, the Technical Connection Conditions (TCC) valid at the time of filing the application shall apply. Network connection modifications include reconstruction, extension, deconstruction or dismantling of a customer installation as well as modification of the maximum apparent power SAmax of a power generation system or modification of the network protection strategy. NOTE 1 If clauses or conditions of the TAB 2007 [3] are referred to in the following, then these are always references to specifically the respective indication of TAB 2007 [3]. In other contexts, the technical connection conditions of the network operators are cited which are generally based on TAB 2007 [3] and which the network operators have to communicate to the relevant regulation authority.
This VDE application guide also applies to standby electric systems (emergency power generators) whose operation in parallel with the public network exceeds the short-time parallel operation permissible for synchronisation of ≤ 100 ms. For power generation systems that are connected on the low-voltage side but also, via a separate customer transformer, to the network operator’s medium-voltage network, the connection point is on the medium-voltage network. For their connection evaluation the BDEW guideline „Erzeugungsanlagen am Mittelspannungsnetz“ [2] shall be used. NOTE 2 In that context, power generation systems, that are connected to a customer owned low-voltage network primarily designed for extraction, may be connected to and operated with a maximum apparent connection power ΣSAmax ≤ 100 kVA (sum all power generation systems connected to that low-voltage network and not meeting the requirements of the BDEW guideline „Erzeugungsanlagen am Mittelspannungsnetz“ [2]) in accordance with the present guideline “Power generation systems connected to the low-voltage distribution network.”
Power generation systems include: –
water-power systems;
–
photovoltaic systems (PV systems);
–
generators mechanically coupled with thermal engines, e.g. in combined heat and power units (CHP);
–
fuel cell systems.
The electrical energy can be generated by synchronous or asynchronous generators with or without inverters of by direct-current generators (e.g. solar cells of photovoltaic systems) with inverters. The maximum apparent connection power up to which connection to the low-voltage network is permissible depends on the type and mode of operation of the power generation system as well as on the network conditions.
2
Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. DIN 18015-2, Electrical installations in residential buildings — Part 2: Nature and extent of minimum equipment DIN 43870, Meter mounting boards DIN 43880, Built-in equipment for electrical installations — Overall dimensions and related mounting dimensions E DIN EN 45011:1998-03, General requirements for bodies operating product certification systems (ISO/IEC EN 45011:1998-1996) DIN EN 50160, Voltage characteristics of electricity supplied by public distribution networks DIN EN 50438 (VDE 0435-901), Requirements for the connection of micro-generators in parallel with public low-voltage distribution networks
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DIN EN 60909-0 (VDE 0102), Short-circuit currents in three-phase a.c. systems — Part 0: Calculation of currents DIN EN 61000-3-2 (VDE 0838-2), Electromagnetic compatibility (EMC) — Part 3-2: Limits — Limits for harmonic current emissions (equipment input current ≤ 16 A per phase) DIN EN 61000-3-3 (VDE 0838-3), Electromagnetic compatibility (EMC) — Part 3-3: Limits — Limitation of voltage changes, voltage fluctuations and flicker in public low-voltage supply systems, for equipment with rated current ≤ 16 A per phase and not subject to conditional connection DIN EN 61000-3-11 (VDE 0838-11), Electromagnetic compatibility (EMC) — Part 3-11: Limits — Limitation of voltage changes, voltage fluctuations and flicker in public low-voltage supply systems; Equipment with rated current ≤ 75 A and subject to conditional connection DIN EN 61000-3-12 (VDE 0838-12), Electromagnetic compatibility (EMC) — Part 3-12: Limits — Limits for harmonic currents produced by equipment connected to public low-voltage systems with input current > 16 A and ≤ 75 A per phase DIN EN 61000-4-7 (VDE 0847-4-7), Electromagnetic compatibility (EMC) — Part 4-7: Testing and measurement techniques — General guide on harmonics and inter-harmonics measurements and instrumentation, for power supply systems and equipment connected thereto DIN EN 61000-4-30 (VDE 0847-4-30), Electromagnetic compatibility (EMC) — Part 4-30: Testing and measurement techniques — Power quality measurement methods DIN VDE 0100-460 (VDE 0100-460), Erection of power installations — Part 4: Protection for safety; Chapter 46: Isolation and switching DIN VDE 0100 (VDE 0100), Erection of low-voltage installations DIN VDE 0100-200 (VDE 0100-200), Low-voltage installations — Part 200: Definitions DIN VDE 0100-410 (VDE 0100-410), Low-voltage electrical installations — Part 4-41: Protection for safety — Protection against electric shock DIN VDE 0100-551 (VDE 0100-551), Low-voltage electrical installations — Part 5-55: Selection and erection of electrical equipment — Other equipment — Clause 551: Low-voltage generating sets DIN VDE 0100-712 (VDE 0100-712), Low-voltage installations — Part 7-712: Requirements for special installations or locations — Solar photovoltaic(PV) power supply systems DIN VDE 0105 (VDE 0105), Operation of electrical installations DIN VDE 0105-100 (VDE 0105-100):2009-10, Operation of electrical installations — Part 100: General requirements DIN VDE 0603 (VDE 0603), Consumer distribution boards and meter panels AC 400 V VDE-AR-N 4400:2011-08, Electricity Metrology (Metering Code)
3 3.1
Terms, definitions and abbreviations Terms and definitions
For the purposes of this document the following terms and definitions apply. 3.1.1 system operator entrepreneur, or a natural or legal person acting on his behalf, assuming the entrepreneur’s responsibility for safe operation and proper condition of the customer’s system, installation or plant (T.N.: in the following always called system)
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3.1.2 system erector persons or enterprises erecting, expanding, modifying or running an electrical installation or system as well as persons or enterprises who, though not having erected, expanded, modified or run this electrical system, have checked the executed works as experts and assume the responsibility for their proper execution 3.1.3 connection owner any natural or legal person (e.g. owner) whose electrical system is connected through a supply connection directly to the network of the network operator NOTE
The connection owner has a legal relationship with the network operator.
3.1.4 automatic reclosing (AR; ge: Automatische Wiedereinschaltung, AWE) reclosing, by an automatic device, of a circuit breaker assigned to a faulty network part assuming that the fault disappears during the time of interruption 3.1.5 rated current Ir current the respective device of installation is designed to be permanently operated with by the manufacturer or on the basis of a standard 3.1.6 three-phase system 3.1.6.1 ideal three-phase system symmetric three phase system with the following characteristics: 1)
electric symmetry of the power generation units, i.e.: a)
the r.m.s. values of the three phase to neutral or line voltages, respectively, are equal,
b)
all voltages have the same frequency f or angular frequency ϖ = 2π f,
c)
the phase displacement between the individual voltages is 120°;
2)
symmetrically designed equipment, i.e. equal positive-sequence and negative-sequence impedances;
3)
symmetric loading
3.1.6.2 real three-phase system three-phase network in which the balance of the line voltages can be disturbed due to the influence of unbalanced loads and power generation systems feeding non-symmetrically 3.1.7 final circuit electric circuit intended to supply directly electric current to current using equipment or socket-outlets 3.1.8 power generation system (ge: Erzeugungsanlage, PGS) all power generation units using the same primary energy carrier (e.g. all PV units) connected to a power port/house connection (also see Annex A) NOTE
Unit symbols relating to the power generation system are given the index “A”.
3.1.9 power generation unit (ge: Erzeugungseinheit, PGU) individual unit for the generation of electrical energy (also see Annex A)
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NOTE 1 For a photovoltaic unit, this may be, e.g., the inverter including the components/solar modules connected downstream (from the network point of view). Thus, a photovoltaic power generation system with two inverters firmly connected to the meter panel consists of two power generation units. NOTE 2
Unit symbols relating to the power generation unit are given the index “E.”
3.1.10 flicker voltage fluctuations producing the subjective impression of fluctuations in the luminance via the functional chain electric lamp—eye—brain 3.1.10.1 short-term flicker strength Pst quantity for the assessment of flicker-effective voltage fluctuations of a time interval of 10 min NOTE
Here, the index “st” indicates short term.
3.1.10.2 long-term flicker strength Plt quantity for the assessment of flicker-effective voltage fluctuations of a time interval of 120 min NOTE
Here, the index “lt” indicates long time.
3.1.11 readily accessible disconnection device aboveground connection point of the house connection cable to the network operator’s low-voltage network (e.g. cable connection cabinet, cable distributor cabinet, transformer station, house connection box), provided that it is freely and readily accessible to the staff of the network operator 3.1.12 customer installation the electrical installation as specified in NAV, § 13 and § 14 and, thus, with the exception of the measuring device(s), all electrical apparatus downstream of the supply point that is used to supply the network users 3.1.13 short-circuit power 3.1.13.1 initial short-circuit power Sk′′ initial symmetrical short-circuit power decisive for the calculation of the short-circuit strength in accordance with DIN EN 60909-0 (VDE 0102): Sk′′ = 3 ⋅ U n ⋅ I k′′
3.1.13.2 ′′ network short-circuit power SkN short-circuit power available on the network side without the share of the power generation system that is to be connected 3.1.13.3 network short-circuit power SkV the network’s short-circuit power (based on the sustained short-circuit power) at the point of common coupling (PCC), which is decisive for the calculation of network interactions NOTE Cf. reference [4]. It is generally lower than the short-circuit power used for rating the short-circuit strength of systems and installations.
3.1.14 short-circuit current I k′′ initial short-circuit current in accordance with DIN EN 60909-0 (VDE 0102) 10
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3.1.15 short interruption short interruption caused by automatic disconnection of a fault followed by an AR or other short-term interruptions 3.1.16 power 3.1.16.1 rated apparent power SrE apparent power that the components of the power generation unit are designed for 3.1.16.2 reactive power Q part of the apparent power that does not contribute to the generation of electrical energy NOTE It is the product of the apparent power and sine of the phase displacement angle ϕ between the fundamental components of the line to neutral point voltage U and the current I.
3.1.16.3 maximum apparent power of a power generation system SAmax ratio of the maximum active power of the power generation system PAmax to the displacement factor cos ϕ prescribed by the network operator P S Amax = Amax cos ϕ NOTE
SAmax is used as a basis for the network connection test.
3.1.16.4 maximum apparent power of a power generation unit SEmax ratio of the maximum active power of the power generation system PEmax to the displacement factor cos ϕ prescribed by the network operator P SEmax = Emax cos ϕ
3.1.16.5 maximum active power of the power generation unit PEmax highest active power of a power generation unit which is obtained as the highest mean value possible during a period of 10 min 3.1.16.6 maximum active power of the power generation system PAmax highest active power of a power generation system resulting from the sum of the maximum active powers of the power generation units PAmax = PEmax
(
∑
)
3.1.16.7 apparent power S product of the r.m.s. values of the line-to-neutral voltage and the current carried by the individual lines 3.1.16.8 active power P electric power relevant for the generation of electrical energy available for conversion into other forms of energy (e.g. mechanical, thermal or chemical) NOTE This is the nominal power of the power generation unit given by the manufacturer for nominal conditions. For calculation purposes, the power of the apparatus on the network side (e.g. the inverters) is to be used.
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3.1.17 power factor λ ratio of the magnitude of the active power P to the apparent power S:
λ=
P S
NOTE Just like P and S, λ relates to the r.m.s. values of the total alternating quantity, i.e. to the sum of their fundamental component and all harmonics.
3.1.18 maximum switching current factor Kimax ratio of the highest current occurring during a switching operation (e.g. starting or connecting current or the highest breaking current under normal operating conditions) to the normal generator current InG. For this, the current is to be considered as an r.m.s. value over a period 3.1.19 medium-voltage network three-phase network of the network operators with a nominal voltage of > 1 kV to < 60 kV 3.1.20 network connection point network point at which the customer system is connected to the network operator’s network NOTE The network connection point is mainly important in the context of network planning. It is not always required to distinguish between the network connection point and the point of common coupling (PCC).
3.1.21 network operator operator of a network of public electricity supply 3.1.22 network impedance angle ψk arc tangent of the ratio of reactance Xk to the resistance Rk of the short-circuit impedance at the network point considered (ψk = arctan (Xk/Rk)) 3.1.23 network and system protection (ge: Netz- und Anlagenschutz, NA-Schutz) type-tested protective device with a conformity certificate in which all protective functions are installed as specified in 6.5 3.1.24 low-voltage network three-phase network of the network operators with a nominal voltage ≤ 1 kV 3.1.25 harmonic oscillation (harmonics) ν sinusoidal oscillation whose frequency is an integral multiple of the fundamental frequency (50 Hz) 3.1.26 adjustable power generation systems photovoltaic systems and all other power generation systems which can be operated in the entire power range of 0 % PAmax to 100 % PAmax 3.1.27 protective device equipment incorporating one or more protection relays and, if necessary, logic elements intended to perform one or more specified protective functions
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3.1.28 self-monitoring function which is normally executed within the protective device and is intended to automatically detect faults within and outside the protective device 3.1.29 voltage 3.1.29.1 rated voltage Ur voltage of a device or installation for which the device or installation has been designed for permanent operation on the basis of a given standard or by the manufacturer 3.1.29.2 operating voltage Ub voltage as the r.m.s. value (10-minute mean value) of the line-to-line voltage occurring during normal operation in a certain point of the network and at a given point in time 3.1.29.3 nominal voltage Un voltage by which a network or system is described or identified 3.1.30 voltage change ΔUmax increase or decrease of the r.m.s. value of a voltage where a distinction is made between slow and rapid voltage change NOTE When indicating a relative voltage change, the voltage change of the line-to-line-voltage is related to the operating voltage of the network:
Δu =
ΔU max Ub
3.1.30.1 slow voltage change voltage increase or decrease (10-minute mean value) usually attributable to changes of the total load/total feed-in in a network or in a part of the network 3.1.30.2 rapid voltage change a single rapid change of the r.m.s. value of a voltage between two consecutive voltage values of certain but not specified durations 3.1.31 over-excited operating condition of a synchronous generator, where the generator absorbs capacitive reactive power from the network 3.1.32 supply point network point which represents the boundary between the network operator’s area of responsibility and that of the operator of the connection system NOTE The supply point is mainly of importance in the context of operation management. It is not always identical with the property line.
3.1.33 transfer factor ü ratio of the rated voltages of high-side and low-side voltage of transformers
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3.1.34 under-excited operating condition of a synchronous generator, where the generator absorbs inductive reactive power from the network 3.1.35 point of common coupling (PCC) point in the public network closest to the customer system to which further customer systems are connected or can be connected NOTE The PCC is generally identical with the network connection point. It is used as a basis for the assessment of network reactions.
3.1.36 displacement factor cos ϕ cosine of the phase angle between the fundamental components of the line to neutral point voltage and the respective current 3.1.47 inter-harmonics μ sinusoidal oscillation whose frequency is not an integral multiple of the fundamental frequency (50 Hz) NOTE
3.2
Inter-harmonics may also occur in the frequency range between 0 Hz and 50 Hz.
Abbreviations
For the purpose of this VDE application guide, the following abbreviations and symbols apply in addition those given in the series of standards DIN EN 50173. AR
Automatic reclosing (ge: Automatische Wiedereinschaltung, AWE)
BGV
Provisions of the institutions for statutory accident insurance and prevention (ge: Berufsgenossenschaftsvorschriften)
CHP
Combined heat and power unit (ge: Blockheizkraftwerk, BHKW)
BKE
Fastening and contacting device (ge: Befestigungs- und Kontaktiereinrichtung)
EMF
Electromotive force (Elektromotorische Kraft, EMK)
PGS
Power generation system (ge: Erzeugungsanlage, EZA)
PGU
Power generation unit (ge: Erzeugungseinheit, EZE)
EL(circuit breaker)
Earth leakage (circuit breaker) (ge: FI(Fehlerstrom)-Schutzschalter)
CHP
Cogeneration of power and heat (ge: Kraft-Wärme-Kopplung, KWK)
NS protection
Network and system protection (ge: Netz- und Anlagenschutz, NA-Schutz)
PEN
Protective earth neutral conductor (ge: Schutz- und Neutralleiter)
PV
Photovoltaic
RCD
Residual Current Protective device (ge: Fehlerstrom-Schutzschalter)
TRA
Audio-frequency centralised ripple control systems (ge: TonfrequenzRundsteueranlagen, TRA)
TRBS
Technical rules for operational safety (ge: Technische Regeln für Betriebssicherheit)
TN-C
Combined protective and neutral conductor (fr: Terre Neutre Combiné)
TN-S
Separate protective and neutral conductor (fr: Terre Neutre Séparé)
TT
Separate protective conductor (fr: Terre Terre)
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4 4.1
General framework conditions Provisions and regulations
Power generation systems shall be erected and operated, taking into consideration the valid provisions and regulations, in such a way that they are suitable for parallel operation with the network operator’s low-voltage network and so that inadmissible reactions on the network or other customer systems are excluded. This also implies that the maximum apparent power of a power generation system SAmax is not exceeded. For the erection and operation of the electrical installations it is imperative to comply at least with: –
the applicable statutory and governmental provisions;
–
the applicable DIN standards and DIN VDE standards, in particular DIN VDE 0100 (VDE 0100) and, thus, also DIN VDE 0100-551 (VDE 0100-551) that has been harmonised on the European level;
–
the occupational health and safety provisions and the accident prevention regulations of the relevant institutions for statutory accident insurance and prevention;
–
the provisions and guidelines of the network operator, in particular the technical connection conditions (TCC).
Any work on the electrical installation downstream of the service fuse shall only be carried out by an electrician who is listed in an electrician’s directory of the network operators. The only exceptions are maintenance works downstream of the measuring device. If justified, the network operator may, on a case-by-case basis, demand modifications and additions to existing systems or to systems to be erected as far as this is required for a safe and disturbance-free supply.
4.2
Application procedure and connection relevant documents
The network operator shall be involved as early as in the planning phase. As a rule, the following documents shall be submitted to the network operator on time and in compliance with the application procedure applicable in accordance with TAB 2007 [3]: –
application for connection to the network (usually a pre-printed form of the network operator, or else the form “Application” given in Annex G.1);
–
site map indicating the plot number and showing the designation and boundaries of the plot as well as the place where the power generation system is to be installed;
–
data sheet with the technical data of the system (see Annex F.2);
–
indication whether the system operator wishes for full or excess feed-in (see Annex F.2);
–
for every power generation unit a certificate of conformity as well as the associated test report. This conformity certificate/test report indicates the electrical characteristics of the power generation unit and confirms its conformity with the requirements of this guideline (see annexes F.3 and G.2);
–
description of the protective devices in accordance with Clause 6 and a certificate of conformity for the network and system protection as well as the associated test report (NS protection; see Clause 6 or the annexes F.4 and G.3, respectively);
–
complete circuit diagram of the power generation system’s connection to the low-voltage network with the data of the apparatus used, incl. the arrangement of the measuring and protective devices as well as the arrangement of the meter panels (that includes decentralized meter panels). Also see Annex B.
4.3
Initial start-up of the power generation system
At the latest one week prior to the scheduled initial start-up of the power generation system, the system erector submits to the network operator the fully completed and signed order for initial start-up. For this, the system erector uses a procedure customary with the network operator. An initial start-up of a power generation system without the network operator’s consent can put the safety of network operation and the power quality in the network at risk and is therefore not permitted. 15
VDE-AR-N 4105:2011 (E)
The date of initial start-up of the power generation system and the date of first parallel operation shall be agreed upon between system erector and network operator. For the initial start-up of heat-led CHP systems with a monovalent mode of operation (no other heat generator present), the start-up should be as quick as possible. The initial start-up of the power generation system is carried out by the system erector. For this, the network operator and system operator have to agree as to whether or not the network operator’s presence is required. The system erector shall prepare an initial start-up protocol (see Annex F.1). The system erector shall confirm on this initial start-up protocol that the power generation system has been erected in accordance with the technical connection conditions listed in this VDE application guide. The completed initial start-up protocol shall be signed in duplicate. One copy shall remain with the system operator and is to be kept as proof of the executed tests. The second copy shall be handed over to the network operator. For the initial start-up of the power generation system the following procedure shall be followed: –
inspection of the system;
–
comparison of the system set-up with the planning specifications;
–
comparison of the set-up of the measuring device for billing purposes with the contractual and technical specifications;
–
execution of a start control procedure for the meters for supply and, if necessary, extraction;
–
check of the connection/disconnection of the external reactive current compensation system with the associated power generation system (if present);
–
for power generation systems with system powers of more than 100 kW: check of the technical equipment for the reduction of the feed-in power within the framework of generation management/feed-in management/network security management;
–
check of the equipment for monitoring the maximum apparent connection power (if monitoring is required by the network operator).
In the case of central NS protection (network and system protection; see Clause 6), the system erector is in addition required to carry out a trigger test in order to test the trigger circuit “NA protection — interface switch.” To this end, the central NS protection is equipped with a test button which when operated activates the interface switch. Activation shall be visualised at the interface switch. The setting value for the rise-in-voltage protection U> in the NS protection closest to the network connection (this may be the central or the integrated NS protection) shall be verified and, if necessary, adjusted to 1,1 Un and it shall be documented in the initial start-up protocol F.1. Both central and integrated NS protections shall be sealed after the initial start-up of the power generation system or else shall be protected by password entry. The password shall not be made available to the system operator.
5 5.1
Network connection Principles for determination of the network connection point
Power generation systems shall be connected at a suitable point in the network, i.e. the network connection point. Based on the documents listed in 4.2, the network operator determines the suitable network connection point that ensures safe network operation, also when taking account of the power generation system, and at which the power applied for can be drawn and transmitted. The decisive aspect for evaluation of the network connection is always the behaviour of the power generation system at the network connection point or at the PCC. This is to ensure that the power generation system is operated without interfering reactions and without affecting the supply of other customers. Annex E shows examples for connection evaluations of power generation systems. 16
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As a rule, power generation systems are connected to the supply point of the extraction system. In individual cases it can be required to create a separate supply point in accordance with TAB 2007 [3] for connection of the power generation system that is connected via a separate network connection line. It shall be ensured that the power generation system is fully separated (electrically) from any other current-using equipment of the customer. The supply point for the current-using equipment shall be marked with a reference to the locality of the supply point for the power generation system. Power generation systems which are installed on different plots with their own respective network connections shall, as a rule, not be connected to the network operator’s network together in the same network connection point. Power generation systems installed on a building with several network connections may be connected to the network operator’s network together at the same network connection point (supply point marking as described above). All separate supply points shall be permanently marked by the supply point owner with the following label “Sectioning point: power generation system/supply network”. For the purposes of evaluating the connectivity with regard to the network reactions, the impedance of the network at the PCC (network short-circuit power, resonances), the maximum apparent connection power as well as the type and operation mode of the power generation system are considered. The evaluation is made assuming the regular switching state and undisturbed operation of the network. If more than one power generation system is connected in the same low-voltage network, their total effect shall be considered. For circuit modifications that are required for maintenance or forced outage reasons, it be required for the determined network connection point to temporarily reduce the power generation system’s output power or to disconnect it from the network. Examples of connections are given in Annex B.
5.2
Rating of the network equipment
Due to their operation mode, power generation systems may cause higher loading of lines, transformers and other network equipment. Therefore, the network operator examines the loading capacity of the network equipment with regard to the connected power generation systems in accordance with the relevant rating regulations. For calculation purposes the maximum apparent power of the sum of all power generation systems
∑ S Amax
and usually the load factor m = 1 shall be used. The only exception are buried cables for the connection of photovoltaic systems for which a load factor m = 0,7 shall be used.
5.3
Permissible voltage change
For undisturbed operation of the network, the amount of the voltage change caused by all power generation systems with a network connection point in a low-voltage network shall at none of the PCCs in this network may a value of 3 % as compared with the voltage without power generation systems: Δua ≤ 3 %
(1)
If stipulated by the network operator and, if necessary, taking into account the possibilities of the static voltage stability it may be permitted in individual justified cases to deviate from this value of 3 %. NOTE Depending on the resulting displacement factor of all power generation systems, the voltage change can be positive or negative, i.e. the voltage may rise or fall.
When calculating the voltage change, the displacement factor shall be taken into account which is provided by the network operator for the maximum apparent connection power of the power generation system SAmax. For determination of the voltage changes for meshed low-voltage networks and high spatially distributed feed-in powers, it is recommended to use complex load-flow calculations.
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5.4 5.4.1
System reactions General
The electrical installations of the customer system shall be planned, constructed and operated so that reactions to the network operator’s network and to the systems of other customers are permanently reduced to a permissible minimum. Should interfering reactions on the network operator’s network occur nonetheless, the customer shall apply measures to his system that are to be coordinated with the network operator. The network operator is entitled to disconnect the power generation system concerned from the network until the deficiencies are corrected. The connection owner provides the network operator with values from the device documents of the manufacturer which are necessary in order to evaluate system reactions (see Annex F.3). If connection of several power generation systems would result in exceedance of the flicker limits at the most unfavourable PCC, then measures shall be taken which result in the flicker limits being complied with at the most unfavourable point. Responsibility for implementation of these measures lies in turn with the system operator whose system contributes the greatest share of flicker strength. 5.4.2
Rapid voltage changes
Voltage chances at the PCC attributable to the simultaneous connection and disconnection of power generation units do not give rise to inadmissible network reactions if the maximum voltage change does not exceed a value of 3 % (related to Un) at the PCC: Δumax ≤ 3 %
(2)
For a value of 3 % the frequency shall not exceed once every 10 min. Depending on the network short-circuit power SkV at the PCC of maximum apparent connection power SEmax of the activated power generation unit and on the ratio of starting current Ia to rated current IrE, the voltage change can be estimated as follows: Δumax = kimax
5.4.3
SEmax I S = a ⋅ Emax SkV I rE SkV
(3)
Flicker
Flicker describes a phenomenon which is characterised by voltage fluctuations whose frequency and amplitude are of a magnitude that causes lamps supplied with this voltage to show disturbing brightness fluctuations. Further details are given in [4]. The measured variable and the evaluation criterion for flicker caused by power generation systems is the long-term flicker strength Plt. For power generation systems with rated currents of up to 75 A, reactions are deemed to be limited sufficiently, if the power generation units comply with the limit values given in DIN EN 61000-3-3 (VDE 0838-3) or DIN EN 61000-3-11 (VDE 0838-11), respectively. Together, all power generation systems in the low-voltage network shall not exceed the following flicker strength at the most unfavourable PCC: Long-term flicker strength: Plt = 0,5 This value also applies to power generation systems with rated currents above 75 A.
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5.4.4
Harmonics and inter-harmonics
The currents of harmonics and inter-harmonics generated by power generation systems shall be included in the conformity check (see Clause 9). For power generation systems reactions are deemed to be limited sufficiently, if the power generation units comply with the following limit values: –
for rated currents of up to and including 16 A per conductor: the limit values of class A (Table 1) specified in DIN EN 61000-3-2 (VDE 0838-2);
–
for rated currents above 16 A and up to and including 75 A per conductor: the limit values of Table 2 and Table 3 specified in DIN EN 61000-3-12 (VDE 0838-12).
If in the standards mentioned above, limit values are explicitly stated for power generation units, then these limit values shall apply. If the limit values of DIN EN 61000-3-2 (VDE 0838-2) or DIN EN 61000-3-12 (VDE 0838-12), respectively, are not complied with, then the maximum permissible harmonic currents Ivzul of a power generation system are calculated from the related harmonic currents ivzul of Table 1 multiplied by the network short-circuit power at the PCC (minus the power generation system’s share in short-circuit power):
Ivzul = ivzul ⋅ SkV
(5)
Table 1 also applies for power generation systems with rated currents above 75 A. If several power generation systems are effective at this PCC, then the currents to be evaluated in accordance with Table 1 are obtained by superposition of the individual currents in accordance with A.3.3. Table 1 — Permissible harmonic currents related to the network short-circuit power SkV that may be supplied in a network connection point Ordinal number ν, μ
Permissible related harmonic current ivzul in A/MVA
3
3
5
1,5
7
1
9
0,7
11
0,5
13
0,4
17
0,3
19
0,25
23
0,2
25
0,15
25 < ν < 40a
0,15 – 25/ν
Even
1,5/ν
μ < 40
1,5/ν
42 < ν,μ < 178b
4,5/ν
a
Odd.
b
Integral and non-integral within a range of 200 Hz with the mid-band frequency ν. Measurement in accordance with DIN EN 61000-4-7 (0847-4-7.)
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Harmonic currents shall be measured in accordance with DIN EN 61000-4-7 (VDE 0847-4-7). NOTE
Of the methods listed in DIN EN of 61000-4-7 (VDE 0847-4-7), the following shall be applied:
–
in the case of harmonics: r.m.s. values of harmonic subgroups;
–
in the case of inter-harmonics: r.m.s. values of inter-harmonic centred subgroups.
Harmonic currents which flow into the power generation system (e.g. into filter circuits) due to a distorted network voltage, are not assigned to the power generation system. The same shall apply if the power generation system works as an active harmonics filter and, due to its operating mode, brings about a continuous reduction of harmonic voltages existing in the network voltage. However, centralised multi-service control systems shall not be inadmissibly affected (see 5.4.7). 5.4.5
Voltage unbalance
If several single-phase power generation systems are connected to the same network connection point, then uniform distribution of the power supplied to the three line conductors shall be aimed for, where a maximum power difference of 4,6 kVA shall not be exceeded. 5.46
Commutation notches
The relative depth of commutation notches dkom through line-commutated inverters shall not exceed the value of
dkom = 5 %
(6)
at the PCC in the most unfavourable operational state (dkom = ΔUkom/ Uˆ n with Uˆ n = the peak value of the nominal voltage Un). 5.4.7
Audio-frequency centralised ripple-control
Audio-frequency centralised ripple-control are usually operated at frequencies between approx. 100 Hz and 1 500 Hz. Information about the locally applied ripple-control frequency can be obtained from the network operator. Broadcasting levels of audio-frequency impulses are normally about 1 % Un to 4 % Un. In principle, power generation systems may inadmissibly influence the ripple-control installations through additional load on the centralised ripple-control transmitting station or through an inadmissibly high reduction of the signal level in the system operator’s network. As a matter of principle, the audio-frequency level caused by the operation of power generation systems shall not be reduced by more than 5 % at any point of the low-voltage network as compared to the operation without power generation systems; power consumption and generation installations shall be taken into account according to their audio-frequency impedance. With this reduction of the audio-frequency level by power generation systems, it is necessary to take account of the fact that power generation systems supplying the network through static inverters without filter circuits do normally not cause a substantial reduction of the ripple-control level. Where filter circuits or compensating capacitors are present, it is necessary to examine whether the short-circuit reactance of the system transformer may give rise to a series resonance. Apart from the limitation of the level reduction, it is not allowed to generate inadmissible interference voltages. The following rules shall apply in particular: –
The interference voltage caused by a power generation system whose frequency corresponds to the locally applied ripple-control frequency or is very close to it (± 5 Hz), shall not exceed the value of 0,1 % Un.
–
The interference voltage caused by a power generation system whose frequency lies at the ambient frequencies of ± 100 Hz to the locally applied ripple-control frequency or in its immediate proximity, shall not exceed a value of 0,3 % Un.
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These limit values as well as further details can be found in the guidelines on audio-frequency centralised ripple control („Tonfrequenz-Rundsteuerung“) [5]. Should a power generation system inadmissibly impair the operation of the centralised ripple-control systems, the operator of the power generation system shall take appropriate remedial measures even if the impairment is noticed at a later date. 5.4.8
Carrier frequent usage of the customer network
If the system operator runs a system with carrier frequent usage of his network, then it shall be ensured by means of suitable devices (e.g. carrier frequency limitation) that interfering influences on other customer systems as well as on the systems of the network operator are avoided. Shared usage of the network operator’s network by the customer is permitted solely with the network operator’s consent for the carrier frequent transmission of signals. 5.4.9
Precautionary measures against voltage drops and voltage interruptions
If power generation systems are sensitive to short-time voltage drops or interruptions of supply, then the customer shall take suitable measures to safeguard the system and to ensure operation operational safety.
5.5
Connection criteria
For the technical execution of connections of the power generation system or the customer system with a power generation system, the technical connection conditions of the network operator shall be considered. If the generated power is fully supplied to the network operator’s network, then the connection line of the power generation system shall be firmly connected to the meter panel within the customer system and the meter panel shall then be executed in accordance with the applicable TCC (currently TAB 2007 [3]). When doing so, supply to the meter panel is always carried out via the upper connection compartment. The exception are those power generation systems that are operated with excess feed-in (e.g. in accordance with EEG [6], § 33 (2) or KWK-G [7], § 4 (3a)). In that case, the power generation systems may also be connected in sub-distributions; ((this also applies to)) photovoltaic systems with a maximum active power PAmax of up to and including 30 kW. The meter panels for feed-in meters Z2 (see Clause 7 and connection examples in Annex B) then shall be executed as follows: a)
for central arrangement: in accordance with the applicable TCC (i.e. at present TAB 2007 [3]);
b)
for decentralised arrangement next to the power generation system in accordance with the applicable TCC (i.e. at present TAB 2007 [3]) or in the small distributor (≥ 2 TE) in accordance with DIN VDE 0603 (VDE 0603), also with top hat rail meter;
c)
for decentralised arrangement in the power generation unit (CE certified unit) taking into consideration the standards for the respective fastening of the chosen meter construction (three point: DIN 43870, BKE unit: DIN 43870, measuring devices for top hat rail mounting in accordance with DIN 43880 Size 1, 2 or 3).
NOTE 1
With regard to item c) above: Mounting space and type of connection are included in the CE certification.
NOTE 2 With regard to item c) above: Extension function “ability to communicate”: The equipment manufacturer shall point out in the technical data sheet that subsequent connection to, e.g., SmartGrid is impossible or else show how such an (internal or external) extension can be achieved.
Connection to a final circuit is not permitted in any circumstance. With regard to that, the system erector shall also exercise special care to check of the electrical installation with respect to line dimensioning and protection. Examples of meter panel configurations are given in Annex C. According to the amended version of DIN VDE 0100-551 (VDE 0100-551), it is not required anymore to have an additional section point for the connection of a power generation system to the network operator’s low21
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voltage network. For this reason, the section point, that had to be accessible at any time, is omitted for new connections of power generation systems to the network operator’s network in future. This has consequences for the network operator with regard to the network operation (see 8.2). As a rule, power generation systems shall be designed and connected to the network as balanced threephase generators (characteristics of a three-phase system are explained in 5.6, the term “three-phase system” is defined in 3.1.6). Power generation systems may also be single-phase connected to the network, if the sum of all single-phase connected power generation units per network connection does not exceed the following:
∑ SEmax ≤ 4,6 kVA per line conductor
(7)
Therefore, it is possible to connect in single phase, distributed to the three line conductors, at maximum 3 × 4,6 kVA = SEmax ≤ 13,8 kVA. As soon as the limits given above are exceeded at the network
∑
connection point, any extension shall be three-phase connected to the three-phase system. This requirement may also be satisfied by communicatively coupling single-phase connected power generation units of the same primary energy carrier. For extensions, the single-phase inverters can be replaced by three-phase inverters (see 5.6.3), thus enabling the 3 × 4,6 kVA single-phase to be used for the power generation units to be newly connected. The communicative coupling between power generation units ensures the power generation system’s balanced supply to the individual line conductors of the three-phase network in accordance with 5.6.3. NOTE Thus, communicatively coupled power generation units act like balanced three-phase inverters ensuring balanced currents even in the event of a failure of individual power generation units.
For all that, the maximum permissible imbalance of 4,6 kVA (design and operational state) at a single network connection point for the sum of all power generation systems applies here as well (see Annex B.4). NOTE Thus, the formerly valid regulation that PV systems may feed-in no more than 110 % of their nominal inverter power is obsolete.
Explanations with regard to the connection criteria are given in Annex A, whereas Annex B shows examples for the connection of power generation systems.
5.6 5.6.1
Three-phase network General
Unbalanced loads or unbalanced feed-in by power generation systems will cause unbalanced currents to occur in balanced three-phase systems which may also lead to unbalanced voltages in the network because of the voltage drops thus caused. The maximum permissible value of the voltage unbalance is specified in DIN EN 50160 as a line voltage product feature. For the purposes of maintaining the symmetric characteristics of the three-phase network, three-phase power generation systems shall have the characteristics described in the following. 5.6.2
Three-phase synchronous generators
Synchronous generators generate an electromotive force (EMF) or synchronous generated voltage (opencircuit voltage), respectively, satisfying the conditions for ideal balance (see Figure 1).
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Figure 1 — Synchronous generated voltage of a synchronous generator as an ideal balanced three-phase system In the event of a short circuit, the currents are limited by three identical “internal resistances” which are assumed to be nearly pure reactances (short-circuit reactance). Figure 2 shows the equivalent circuit diagram of a synchronous generator for the case of a short circuit. For a salient-pole synchronous generator the following applies by way of approximation: xg′′ = xd′′ (p. u.).
Figure 2 — Equivalent circuit diagram of a synchronous generator for the case of a short circuit Due to the balance of the synchronous generated voltage and the small short-circuit reactance of the generator ( xd′′ << 1 ), unbalanced currents in synchronous generators lead to only small asymmetries at the terminal voltages of the generator. The generators are — in terms of symmetric components — able to deliver currents not only in the positive sequence system, but also in the negative sequence system and, given a suitable connection, also in the zero sequence system. This way, voltage unbalance is counteracted by the supplied generator currents. 5.6.3
Three-phase inverter systems
For three-phase power generation systems with network feed-in over inverters, the power shall be fed threephase balanced into the three line conductors. The inverter circuit shall preferably be set up as a three-phase current unit. A circuit of single-phase inverters is deemed to be technically equivalent, if these inverters feed three-phase balanced into the three line conductors by means of a suitable communicative coupling. In the medium term, three-phase inverter systems shall provide all the three-phase related functions of the three-phase synchronous generators.
5.7 5.7.1
Behaviour of the power generation system at the network General
Automatic disconnection from the network is not permitted for frequency deviations within the range of 47,5 Hz to 51,5 Hz. The mode of action is described in detail in 5.7.3.3 and 5.7.3.4. Implementation of the frequency dependent active load control is carried out in the open-loop control of the power generation units.
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5.7.2
Maximum permissible short-circuit current
Due to operation of a power generation system, the short-circuit current of the low-voltage network is increased by the short-circuit current of the power generation system. Therefore, information about the shortcircuit current of the power generation system to be expected at the network connection point has shall be provided in accordance with 4.2. For determination of the short-circuit current contributed by the power generation system the following roughly estimated values can be assumed: –
for synchronous generators: 8 times the rated current;
–
for asynchronous generators: 6 times the rated current;
–
for generators with inverters: 1 time the rated current.
If the power generation system gives rise to a short-circuit current increase in the network operator’s network in excess of the rated value, then connection owner and network operator shall agree upon appropriate measures limiting the short-circuit current from the generating facility. 5.7.3 5.7.3.1
Active power output Basics
In the following cases, the network operator is entitled to require and to carry out a system shot-down: –
potential danger to the safety of system operation;
–
congestion or risk of overload on the network operator’s network;
–
risk of islanding;
–
risk to the steady-state or dynamic network stability;
–
rise in frequency endangering the system;
–
repairs or execution of construction measures;
–
operation of network stand-by systems;
–
resynchronisation of sub-networks;
–
within the scope of the generation management/network security management (see 5.7.3.2.)
5.7.3.2
Generation management/network security management
Power generation systems with a system power of more than 100 kW shall be able to reduce their active power in steps of not more than 10 % of the maximum active power PAmax. For every operational state and from each and every operation point, it shall be possible for this power to be reduced to a set point provided by the network operator. This set point is generally provided at the network connection point gradually or continually and it corresponds to a percentage related to the maximum active power PAmax. In the past, the following values have been shown to be suitable: 100 %/60 %/30 %/0 %. (Still, the generated power may also be lower. If all else is technically impractical, then this may also be achieved by shutting down the power generation system.) The network operators do not interfere with the open-loop control of the power generation systems. They are merely responsible for the signalling. Dry contacts are normally used for this. The sole responsibility for the reduction of feed-in power lies with the system operator. For this, the contractual conditions have to be taken into consideration, in particular if this leads to the customer system extracting power. Variable power generation systems shall carry out the power output reduction to the respective set point immediately, however, at maximum within a minute. It shall be technically possible for these power generation systems to reduce the power to the set point 10 % without automatic disconnection from the network, and only at a value of less than 10 % of the maximum active power PAmax are they permitted to disconnect from the network. All other power generation systems shall carry out the power output reduction to the respective set point within a maximum period of five minutes. If the set point is not reached within five minutes, then the power generation system shall be disconnected.
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5.7.3.3
Active power feed-in at overfrequency
At frequencies between 50,2 Hz and 51,5 Hz, all adjustable power generation systems shall reduce (for frequency increase) or increase (for frequency decrease) the active power PM generated instantaneously (at the time of exceeding the mains frequency 50,2 Hz; freezing the value on the current level) with a gradient of 40 % of PM per Hertz (see Figure 3). From this, it follows that the power generation unit will continuously move up and down the frequency characteristic curve in the frequency range of 50,2 Hz to 51,5 Hz with regard to its active power feed-in (“running along the characteristic curve”). The increment of the frequency measurement shall be ≤ 10 MHz. If the mains frequency drops again to a value below 50,2 Hz and if the possible generation power is greater at that instant than the active power PM (frozen value, see above), then the increase of the active power supplied to the network operator’s network shall not exceed a gradient of 10 % of the maximum active power PAmax per minute. At mains frequencies > 51,5 Hz, the power generation system shall disconnect from the network immediately (see 6.5.2).
ΔP = 20 PM
50,2 Hz − f mains for 50,2 Hz ≤ fmains ≤ 51,5 Hz 50 Hz
Where:
PM
is the power generated at the time of exceeding 50,2 Hz;
P
is the power reduction;
fmains
is the mains frequency.
There are no restrictions for frequencies of 47,5 Hz ≤ fmains ≤ 50,2 Hz. Disconnection from the network is required for fmains ≤ 47,5 Hz and fmains ≥ 51,5 Hz. Figure 3 — Active power reduction at overfrequency As an alternative to active power reduction at overfrequency, non-variable power generation systems are permitted to disconnect from the network in the frequency range of 50,2 Hz to 51,5 Hz; in that case, uniform distribution of the disconnection frequency in maximum increments of 0,1 Hz shall be ensured by the manufacturer for every type of system. Power generation systems that are variable under certain conditions, e.g. only within the range of 70 % PAmax to 100 % PAmax, are permitted to be adjusted in correspondence to the characteristic curve. Outside the adjustable range disconnection is then carried out in correspondence to the evenly distributed shut-down limit curve. Linear generators, such as corresponding stirling engines with a maximum apparent power SAmax of up to an including 30 kVA are exempt from this regulation; for frequencies between 50,2 Hz and their maximum frequency upper limit, they are permitted to stay connected to the network and they may disconnect if this upper limit is exceeded, however, at the latest when a frequency of 51,5 Hz is reached or exceeded. In the event of the disconnection frequency being exceeded, the power generation system shall disconnect from the network within a maximum period of one second.
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VDE-AR-N 4105:2011 (E)
5.7.3.4
Active power feed-in at underfrequency
For frequencies between 47,5 Hz and 50,0 Hz, automatic disconnection from the network as a result of a frequency deviation is not permitted (however, linear generators, such as corresponding stirling engines with a maximum apparent power SAmax ≤ 30 kVA, are exempt from the 47,5 Hz requirement because they are currently considered to be of minor system relevance). 5.7.4
Principles for network support
As a rule, power generation systems shall be able to contribute to the static voltage stability in the network operator’s network. Static voltage stability is understood to be the voltage stability in the low-voltage network at which the slow voltage changes are maintained within compatible limits in the distribution network. If required due to network related circumstances and by the network operator, then the power generation systems shall contribute to the static voltage stability in the low-voltage network. A dynamic grid support, i.e. voltage stability in the event of voltage drops in the higher voltage levels, is not required for power generation systems feeding into low-voltage networks. 5.7.5
Reactive power
Irrespective of the number of feed-in phases, power generation systems shall allow for operation under normal stationary operating conditions in the voltage tolerance band Un ± 10% and in their permissible operation points starting with an active power output of more than 20 % of the rated active power with the following displacement factors cos ϕ: –
power generation system
∑ SEmax ≤ 3,68 kVA:
cos ϕ = 0,95under-excited to 0,95over-excited in accordance with DIN EN 50438 (no default given by the network operator); –
power generation system 3,68 kVA <
∑ SEmax ≤ 13,8 kVA:
characteristic curve provided by the network operator within cos ϕ = 0,95under-excited to 0,95over-excited (see Figure 4); –
power generation system
∑ SEmax > 13,8 kVA:
characteristic curve provided by the network operator within cos ϕ = 0,90under-excited to 0,90over-excited (see Figure 5). In the load-reference arrow system, this means the operation in Quadrant II (under-excited) or III (overexcited).
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VDE-AR-N 4105:2011 (E)
Figure 4 — Limit power range for the reactive power of a power generation system within the SEmax ≤ 13,8 kVA (load-reference arrow system) range of 3,68 kVA <
∑
Figure 5 — Limit power range for the reactive power of a power generation system within the SEmax > 13,8 kVA (load-reference arrow system) range of
∑
Within the hatched triangles for the reactive power limit shown in Figures 4 and 5 the reactive power of the power generation system shall be freely adjustable. Upon a change in the active power, the reactive power shall be able to adjust itself automatically in correspondence to the predefined cos ϕ. Type and set points of the reactive power setting will be determined by the respective network conditions and can therefore be provided individually by the network operator within the triangles for the reactive power limit. For power generation systems, whose power generation units feed over inverters or synchronous generators capable to generate reactive power, it is permitted to provide as default either: a)
a displacement factor/active power characteristic curve cos ϕ (P); or
b)
a fixed displacement factor cos ϕ.
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VDE-AR-N 4105:2011 (E)
If the network operator provides a characteristic curve, then any set point resulting from that curve shall be set automatically on the power generation unit within 10 seconds. As a rule, characteristic curve based regulation shall not be applied for power generations systems with generators directly coupled to the network which, due their very operational principle, cannot control the reactive power and, therefore, use constant capacities (such as CHP with asynchronous or linear generators). In that case, the network operator provides a fixed displacement factor cos ϕ. For power generation units with a generator directly coupled to the network, a transition period between startup and reaching the reactive power set point of 10 minutes is permitted. Implementation of the reactive power requirements is carried out at the generator terminals of the power generation units. NOTE 1 A characteristic curve cos ϕ (P) may be provided by the network operator for power generation units feeding with fluctuating power. Such power generation units include, e.g., PV systems or CHP with a generator coupled via inverters. NOTE 2 A fixed displacement factor is appropriate for power generation units feeding with constant power, such as CHP with a generator coupled directly to the network (see example in E.2). Compliance with this default value can be realised by means of suitable capacitors. In that case, characteristic curve control by the power generation units is not required. NOTE 3 In addition to these procedures which are always noncritical with regard to the network voltage stability, it is possible also for net voltage dependent procedures to be used in the future, such as the Q(U) characteristic curve method known from the higher voltage levels.
In conjunction with the connection approval, the network operator informs the applicant about the default for the reactive power setting. Modification of the default or of the procedure by the network operator shall be implemented by the connection owner. Figure 6 shows the standard characteristic curve for cos ϕ (P).
*)
Depending on
∑ SEmax Figure 6 — Standard characteristic curve for cos ϕ (P)
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NOTE 4 The power generation units should be delivered with the standard characteristic curve for cos ϕ (P) shown in Figure 6. Depending on network topology, network load and feed-in power, the network operator can also require a characteristic curve differing from the standard characteristic curve for cos ϕ (P). NOTE 5
6
Explanations with regard to reactive power are given in Annex A.
Construction of the power generation system/network and system protection (NS protection)
6.1
General requirements
The network and system protection (NS protection) is a type-tested protective device with a conformity certifycate (see Annex G.3) in which all protective functions specified in 6.5 are installed. The NS protection acts on the interface switch in accordance with 6.4. The NS protection shall be realized as central NS protection at the central meter panel. For power generation systems of ≤ 30 kVA it is also permitted to have an NS protection installed in the power generation unit(s). Depending on the sum of the maximum apparent powers of all power generation systems connected to the same network connection point, S Amax , the following conditions apply for the NS protection:
∑
–
–
∑ S Amax > 30 kVA
•
∑ S Amax ≤ 30 kVA
•
Central NS protection at the central meter panel or decentralised in a subdistribution or
•
integrated NS protection.
NOTE 1
Central NS protection at the central meter panel Exception: In the case of combined heat and power units, an integrated NS protection is permitted also for power generation systems of > 30 kVA, if there is a disconnection device available at the network connection point that is accessible for the network operator’s staff at any time.
The information given in 6.5.2 shall be taken into account.
NOTE 2 As a rule, the first to inform in the event of a relay of the integrated NS protection being tripped is the system erector since the cause for the tripping may also lie somewhere in the customer system. The network operator has to be informed in the event of a relay of the central NS protection being tripped. NOTE 3
When determining the sum of the maximum apparent powers of all power generation systems connected to the
same network connection point
∑ S Amax , it is necessary to consider all existing as well as all new systems. Combined
heat and power units that are connected via a disconnection device that is accessible at any time are not taken into consideration when determining
∑ S Amax .
The loss of the auxiliary voltage of the central NS protection or the control of the integrated NS protection shall lead to an instantaneous tripping of the interface switch. Tripping of a relay of the integrated protection shall not be inadmissibly delayed by other functions of the control system in order to ensure that the required disconnection periods are kept. The protective functions shall be maintained even in the event of a malfunction in the system control. Single-fault tolerance shall be ensured for both central and integrated NS protection (see explanations in A.6).
6.2
Central NS protection
The central NS protection shall be accommodated as independent apparatus in a suitable circuit distributor in accordance with TAB 2007, Clause 8, Paragraph 1, and not in the upper connection compartment specified in TAB 2007, 7.2, Paragraph 9 and connected to the central meter panel. It shall allow for sealing or for password protection. Examples for the arrangement of central NS protection and, thus, for the connection of power generation systems to meter panels are given in Annex C. 29
VDE-AR-N 4105:2011 (E)
For central NS protection, it is in addition required to carry out a trigger test for the purposes of checking the actuation circuit “NS protection — interface switch”. To this end, the central NS protection has a test button which when operated activates the interface switch. Activation shall be visualized at the interface switch. NOTE If a power generation system is connected via several meters, then a interface switch is required for each of the separate outgoing feeders. These interface switches are activated over an NS protection (see Annex B).
6.3
Integrated NS protection
In the case of integrated NS protection, the NS protection can be integrated in the programmable system control of the power generation units (e.g. in the inverter control). If so, then both the test button and the sealing may be omitted, however, password protection is required, if the protective function U > is adjustable. The integrated NS protection acts on an integrated interface switch (see 6.4.3).
6.4
Interface switch
6.4.1
General
For the connection of the power generation system to the network operator’s low-voltage network or to the remaining customer system, it is necessary to use a interface switch. It consists of two electric switching devices connected in series and shall thus be constructed redundantly. The interface switch is controlled by the NS protection and activates automatically if at least one protective function responds. The interface switch may connect both the entire customer system to the network and the power generation system to the remaining customer system. Unless isolated operation is intended, the switching devices of the individual power generation units (integrated interface switch) may be used for this. NOTE case, for
It is also possible to use the integrated interface switches in connection with the central NS protection. In any
∑ S Amax > 30 kVA (sum of the maximum apparent powers of all power generation systems connected to the
same network connection point; for the exception see 6.1) the central NS protection is to be connected directly at the central meter panel; the maximum disconnection time of 200 ms shall on no account be exceeded and it is required to carry out a trigger test.
The break devices of the interface switch shall be designed to be short-circuit proof and shall be releasable without delay and with due regard to the protective devices required by Clause 6.5. The breaking capacity of the two break devices of the interface switch shall be dimensioned at least in accordance with the responding range of the upstream safety fuse or the maximum short-circuit current contribution of the power generation system. Switches with at least breaking capacity shall be used for both break devices of the interface switch. In addition to that, all-pole disconnection shall be ensured (see explanations in A.7). The response time of the interface switch shall be given in the manufacturer documents. The short-circuit strength of the entire electrical installation shall be demonstrated by the connection owner based on the technical connection conditions. Connection examples are given in Annex B. 6.4.2
Central interface switch
The two break devices of the central interface switch shall be executed as galvanic break devices (e.g. mechanical contactors (only for power generation systems with SAmax ≤ 100 kVA), protective motor switch, mechanical circuit breaker); a separating function in accordance with DIN VDE 0100-460 (VDE 0100-460) is not required.
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VDE-AR-N 4105:2011 (E)
The two break devices of the interface switch shall be installed directly at the central meter panel in the circuit distributor of the power generation system. Examples for the arrangement of interface switches and, thus, for the connection of power generation systems to meter panels are given in Annex C NOTE The two break devices connected in series do not ensure single-fault tolerance within the meaning of the explanations given in A.6. A single fault can safely be treated, but is, however, not detected and does therefore not cause the power generation system to be disconnected.
6.4.3
Integrated interface switch
Construction of the interface switch shall be carried out taking into consideration the single-fault tolerance (see the explanation given in A.6). A interface switch (e.g. power relay, mechanical contactor, mechanical circuit-breaker, etc.) ensures a singlefault tolerant all-phase galvanic breaking. NOTE The integrated interface switch does not ensure separation in accordance with VDE 0100-460 (VDE 0100-460). This shall instead be realized for servicing works by an additional suitable break device that is not part of the interface switch (e.g. line safety switch).
For power generation systems with inverters, the interface switch shall be provided on the inverter’s network side. A short circuit in the inverter shall not impair the switching function of the interface switch.
6.5
Protective devices for the interface switch
6.5.1
General
The purpose of the NS protection is to disconnect the power generation system from the net in the event of inadmissible voltage and frequency values (also see DIN VDE 0100-551 (VDE 0100-551), 8.2.) This is intended to prevent an unintentional feed-in of the power generation system into a power-supply unit separated from the remaining distribution network as well as the feed-in of faults within this network. The specifications given in 6.5.2 do not refer to the protective functions short-circuit protection, overload protection, protection against electric shock and all-phase separator of the circuit to the power generation system (e.g. by means of line circuit breakers, earth leakage circuit breakers) which shall be executed in accordance with the applicable VDE regulations and for which the connection owners are themselves responsible (to ensure self-protection). In this respect, the protection function described in this VDE application guide may have to be extended by the connection owner as appropriate to the power generation system. However, the self-protection shall not undermine the requirements described in this VDE application guide. The system operator shall himself take precautions to prevent damages to his systems and installations as might be caused by switching actions, voltage fluctuations and automatic reclosings in the network connected upstream or other processes in the network of the network operator. The following functions of the decoupling protection shall be implemented: –
voltage drop protection
U<;
–
rise-in-voltage protection
U>;
–
rise-in-voltage protection
U>>;
–
frequency decrease protection
f<;
–
frequency increase protection
f>;
–
islanding detection.
Voltage protection devices should utilise the half-wave r.m.s. value. For this, using the 50 Hz fundamental component is sufficient. Only the rise-in-voltage protection U> shall be designed as 10-minute running mean value protection which prevents the upper voltage limit specified in DIN EN 50160 from being exceeded (monitoring of the power 31
VDE-AR-N 4105:2011 (E)
quality). For this, formation of a new 10-minute mean value at least every 3 seconds is sufficient, which is then to be compared with the setting value for U> given in Table 2. Voltage protection devices shall be constructed so, that they monitor the supplying (feeding) line conductors. For power generation systems of up to 30 kVA, the voltage(s) (per line conductor supplied) shall be measured between the line conductors and the neutral conductor. Voltage protection devices for power generation systems of more than 30 kVA shall be constructed as threephase equipment. To this end, the three voltages between the line conductors and the neutral conductor shall be measured; the three line-to-line conductor voltages shall either be determined arithmetically from the three line-to-neutral voltages or else also be measured separately. Thus, recording of 2 × 3 voltage values is required for this. The voltage values shall be composed by disjunction (logical OR). Disjunction means in this case that: –
for rise-in-voltage protection relays, exceeding the threshold value leads to an excitation for at least one measuring voltage;
–
for voltage-drop protection relays, a drop below the threshold value leads to an excitation for at least one measuring voltage.
Frequency protection devices may be designed as single-phase equipment. The setting values of the protective functions and the last five dated failure reports (a relative time stamp is sufficient, i.e. a real time clock is not required) shall be readable at the NS protection. Interruptions of supply with durations of 3 s or longer shall not lead to loss of any of the failure reports. Read-out shall be possible at the central NS protection irrespective of the operational state of the power generation system and without any additional aids (such as a display). For integrated NS protection read-out may be carried out using a data interface. Power generation systems with integrated NS protection and a maximum apparent power SAmax ≤ 4,6 kVA are exempt from the requirements of this paragraph until 2012-12-31. 6.5.2
Protective functions
Except for the rise-in-voltage protection U>, all protective functions shall be firmly set in the NS protection (i.e. so as to be unalterable). The protective functions of the NS protection shall be designed so that the disconnection time (i.e. the sum of the proper times of NS protection and interface switch plus a delay for the protection relay, which may or may not be adjustable) does not exceed 200 ms. The following protective functions shall be set in the NS protection.
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VDE-AR-N 4105:2011 (E)
Table 2 — Setting values for the NS protection Protective function
Protection relay setting values*
Voltage drop protection
U<
0,8 Un
< 100 ms
Rise-in-voltage protection
U>
1,1 Un**
< 100 ms
Rise-in-voltage protection
U>>
1,15 Un
< 100 ms
Frequency decrease protection
f<
47,5 Hz
< 100 ms
Frequency increase protection
f>
51,5 Hz
< 100 ms
*
The duration set point “< 100 ms” for the protection relay setting value is based on the assumption that the maximum proper time for both NS protection and interface switch is also 100 ms. This leads to a maximum total disconnection time of 200 ms. If the proper time of a component is less than 100 ms (e.g. 50 ms), then this allows for a longer period during which to perform the measurements and evaluation of the protective function (e.g. up to 150 ms). This could then lead to a protection relay setting value higher than “< 100 ms”, i.e. “< 150 ms”. However, in that case, only the 100 ms shall be visualised as setting value at the NS protection. Still, the disconnection time of 200 ms shall not be exceeded under any circumstance.
**
It shall be ensured, that the voltage at the network connection point cannot fall below 1,1 Un. If compliance with this requirement is ensured by a central NS protection, then it is permissible to set the rise-in-voltage protection at the decentralised power generation unit or system to a value of up to 1,15 Un. In that case, the system erector should consider any possible effects on the customer installation. Combination of central NS protection (U>: 1,1 Un) and integrated NS protection (U>: 1,1 to 1,15 Un) is advisable, if the voltage drop does in the house installation cannot be neglected. This is typically the case with longer connection lines.
If only an integrated NS protection is used for power generation systems of up to 30 kVA, then the value of the rise-in-voltage protection U> of 1,1 Un shall not be changed. The admissible tolerance between setting value and trip value of the voltage shall be at maximum ± 1 % and the admissible tolerance for the frequency at maximum ± 0,1 %. The conditions for connection/re-connection of the power generation system are described in 8.3. 6.5.3
Islanding detection
For power generation systems, islanding detection shall be carried out using one of the following methods: a)
active method, e.g. by means of a frequency shift method (generally for PV systems);
b)
passive method by means of the three-phase voltage monitoring (possible only for power generation systems without inverters or for single-phase power generation units with inverters).
Method a) shall be verified by means of a resonant circuit test, whereas method b) shall be verified at an AC voltage source (see Annex D). NOTE In special cases it may be necessary to use additional protective functions (e.g. vector surge or load step relays) in order to ensure decoupling or safe network operation. This is the case, e.g., if the output of power generation systems with rotating machines amounts to more than 20 % of the output of PV systems using the frequency shift method in the same local network. If so, then more powerful power generation systems should be equipped with rotating machines with vector surge relays.
The islanding detection is implemented in the central NS protection or in the integrated NS protection of the power generation unit. If an islanding detection system acting on the integrated interface switch is integrated in all power generation units of a power generation system, then it is permitted to omit the islanding detection in the central NS protection regardless of the system power. Detection of an isolated network and disconnection of the power generation system by means of the interface switch shall be completed within 5 seconds.
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VDE-AR-N 4105:2011 (E)
7
Metering for billing purposes
Installation and operation of the measuring device Z1 shall comply with VDE-AR-N 4400:2011-08 (formerly BDEW guideline “Metering Code” [8]), the VDN guideline „Technische Anschlussbedingungen für den Anschluss an das Niederspannungsnetz“ (Technical connection conditions for connection to the low-voltage network; TAB 2007 [3]) as well as the connection conditions of the network operator. Load-profile meters shall be used for system powers of more than 100 kW. Installation and operation of the measuring devices shall be agreed in due time between the system operator and the network or metering point operator, respectively. According to the German Calibration Act (Gesetz über das Mess- und Eichwesen or Eichgesetz for short), only certified and calibrated meters and transformers shall be used in the course of business. A two-direction meter shall preferably be used as meter Z1 (see C.4.3) for extraction from the network operator’s network and for feed-in into the network operator’s network; alternatively, it is possible to use, for system powers of up to 100 kW, one backstop measuring device each for extraction and feed-in on separate meter sections. The execution shall be co-ordinated with the network operator. The measuring devices (Z1) used for extraction and feed-in in conjunction with power generation systems shall be constructed so that a measurement procedure balancing over all phases is ensured separately for the two current flow directions. Electronic three-phase meters shall be parameterised in accordance with the Ferraris principle with regard to the backstops and recording of two directions. Therefore, the meter point-related balance shall first be calculated for the three line conductors after which it is required to apply the “backstop” function to this balance or to carry out the allocation to the meter “extraction” or “feed-in”, respectively. In order to ensure correct metering of the generation quantities supplied to the customer system in accordance with EEG 2009 [6], § 33 (2) or of the CHP net current generation in accordance with KWK-G 2009 [7], § 4 (3a), the only meters to be installed as meter Z2 (see C.4) shall be backstop meters. Separate meters Z2 shall be installed for each type of system (e.g. PV or CHP system). A separator shall be installed between the meter Z2 and the customer system (see Figure C.6 and Figure C.7 of C.4.3). It is not permitted to allocate the three line conductors of a power generation unit feeding into the three-phase system to different measuring devices (e.g. for full feed-in and excess feed-in). For photovoltaic systems with a maximum active power PAmax of up to 30 kW and for CHP systems the system operator is free to chose whether to install the measuring device Z2 at a central meter panel in accordance with TAB [3] or next to or inside the power generation unit (see 5.5). In addition, the metrological framework conditions (e.g. temperature, humidity, operating position, mechanical influences) shall be adhered to. NOTE [9].
This regulation replaces the specifications given in „Ergänzung zu den TAB 2007“ (Supplement to TAB 2007)
The minimum requirements for the accuracy classes of the measuring devices are prescribed by the respective network operator. As a rule, the following accuracy classes shall be provided: –
energy meters:
Class 2 (active energy);
–
load-profile meters:
Class 1 (active energy) or Class 2 (reactive energy);
–
current transformers: 0,5S.
In the case of load-profile meters, the system operator shall maintain a communication connection that can be used for remote transmission of the metered values. Data recorded by the network operator are treated as confidential and will only be made available to authorised persons. The line colours for meters directly connected to a meter panel in accordance with TAB 2007 [3] shall be chosen as specified in DIN 43870-3: –
lines “lower connection compartment → meter”:
–
lines “meters → main line branch terminal in the upper connection compartment”:
black brown
The meter section shall be marked so, that the label “power generation system” is durable and easily readable. 34
VDE-AR-N 4105:2011 (E)
8 8.1
Operation of the system General
The operation of electrical installations includes all technical and organisational activities required to ensure the functional efficiency and safety of the systems. These activities include all operating measures as well as electrical and non-electrical operations as described in the applicable rules and regulations. Particular reference is made to DIN VDE 0105-100 (VDE 105-100). The system operator is responsible for the operation of the power generation system. If required by the network operator, the system operator shall name an electrically skilled person able to carry out the required works on the system operator’s electrical installation. For connection of the power generation systems, the conditions given in 8.3 shall be satisfied. During operation, the conditions of Clause 5, which the decisions regarding the connection of the power generation system were based on, shall only be changed with the consent of the network operator. The system operator shall ensure that the equipment required for parallel operation with the low-voltage network is always in proper technical condition. To this end, it is required to have an electrically skilled person check the switches and protective devices for proper functioning at regular intervals. This requirement is deemed to be satisfied for normal operating and environmental conditions if the test intervals mentioned in BGV A3 or TRBS 1201 are adhered to. The repeat tests shall include at least the following: –
check of the environmental conditions (pollution, mechanical or isolation damages) and elimination of deficiencies, if required;
–
tripping control of the interface switch.
The result shall be recorded in a test protocol which shall be submitted to the network operator upon request. Regular repeat tests of the NS protection, the interface switch and the functional chain NS protection— interface switch may be omitted if a routine test has been conducted in the context of conformity checks (see G.3) and if a test certificate issued by a certification body appropriately accredited by DAkkS, the Deutsche Akkreditierungsstelle (i.e. the national accreditation body of the Federal Republic of Germany) in accordance with DIN EN 45011 is available. In justified cases, the network operator can require a check of the NS protection and the interface switch in order to demonstrate their proper functioning. Power reduction or disconnection required due to network conditions Upon request of the network operator, the system operator is obliged to switch off the power generation system or to disconnect it from the network if this is required for conducting works that are necessary for operational purposes in the network operator’s network. Scheduled disconnections shall be announced to the system operator in a timely and suitable manner. In case of danger, breakdown or risk to network security, the network operator is entitled to immediately disconnect the power generation system from the network or to reduce its active power, respectively. In the event of the agreed maximum connection power being exceeded the network operator is entitled to disconnect the power generation system from the network. To this end, the network operator may require of the system operator to install adequately designed technical equipment that will separate the power generation system from the network operator’s network as soon as certain limit values (e.g. the maximum apparent connection power) are exceeded. If the network operator detects serious defects in the power generation system concerning the safety of persons and systems, then they are entitled to disconnect the system parts concerned from the network until the defects are rectified.
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Access Upon co-ordination with the system operator, the network operator shall be granted access to all components of the power generation system (meter panel, central NS protection (if available), interface switch, facilities of the power generation/network security management (if available), and the power generation units). Exchange of information The network operator will inform the system operator about substantial modifications in his network which will have an impact on the current parallel operation. The system operator shall, in due time, co-ordinate with the network operator any scheduled modifications to his power generation system which will have an impact on the parallel operation or the decoupling protection, such as increase or decrease of the system power, replacement of protective devices or modifications to the compensation equipment. Coupling of network connection points Different network connection points on the network of the network operator(s) shall not be operated in galvanic connection through systems of one or more system operator(s). Behaviour in the event of disturbances The reconnection conditions given in 8.3 shall be satisfied. The system operator shall immediately inform the network operator about any incidents detected as far as they are of importance to the network operator. Due to the possibility of voltage recovery at any time after an interruption of supply, the network connection point is to be considered to be constantly energised. Reconnection is usually carried out by the network operator without prior consultation with the system operator. Fault clearance may require unscheduled investigations and measurements which the network operator and the system operator shall carry out on their respective operating equipment. For fault clearance and remedy, the network operator and the system operator shall provide mutual support. All information required for fault clearance shall be exchanged between them.
8.2
Particular characteristics of the management of the network operator’s network
Earthing and short-circuiting for works on the network After isolation, a prerequisite for the safety of works on the network is to prevent any voltage sources from reconnecting unintentionally. Due to the fact that spurious actions can never be excluded and that the hitherto common separating device that was to be accessible to the network operator at any time is omitted, the working methods permitted in accordance with DIN VDE 0105-100 (VDE 0105-100):2009-10 are earthing and short-circuiting in accordance with DIN VDE 0105-100:2009-10, 6.4.2 or live working in accordance with DIN VDE 0105-100:2009-10, 6.3. Earthing and short-circuiting are required upstream as well as downstream of the point where the work is done. For this, sufficiently dimensioned house connection boxes should also be used. This means that network operators are required to consistently apply all five of the safety rules when works are carried out on the low-voltage network (with the exception of live working). In future, it is therefore required also to provide earthing and short-circuiting downstream of a disconnected line in the network operator’s low-voltage network (when viewed from the local network transformer, i.e. on the customer side of the splitting point). If earthing and short-circuiting are not provided on the customer side of the splitting point, then third-party feed-in (e.g. via an emergency power generator as used in farming) shall be prevented by other means. Operation of network stand-by systems For certain works on the network (e.g. replacement of a local network transformer), the network operator has to disconnect sub-networks from the remaining network. In order to ensure continuous supply to the 36
VDE-AR-N 4105:2011 (E)
customers during this time, the network operator may use network stand-by systems. Normally, the network operator will inform the customers concerned about the use and operation of network stand-by systems. However, if the feed-in power of the power generation systems exceeds the load extraction in this separated sub-network, it is possible for the network stand-by system to be disconnected by the protection system. Stable operation of the network stand-by system would then no longer be possible. In order to prevent this from happening, care shall be taken that the power generation systems are and remain disconnected in the event of such an operating state. To this end, the network stand-by system is connected and started in parallel to the low-voltage network. After that, the local network transformer is switched off and the network stand-by system takes over supply of the “network island”. In case of a power surplus in the low-voltage network, the network stand-by system shall be able to temporarily “stave off” the surplus power. Therefore, the network stand-by system shall be set to 52,0 Hz for a short time so that all power generation systems can safely disconnect themselves from the network. Transition to the “operating frequency” of the network standby system of 50,5 Hz to 51,0 Hz is to be achieved in a matter of seconds (approx. 10 seconds). Given that operating mode, almost all power generation systems will remain separated from the network operator’s network (prior to this VDE application guide, the reconnection criterion has mostly been 50,2 Hz; starting with the application of this VDE application guide, it will be 50,05 Hz; see 8.3). In order to enable uninterrupted resynchronisation of the sub-network with the rest of the network, the frequency is realigned to the current mains frequency once operation of the network stand-by system is ended and the local network transformer is returned to service. In order to prevent the power generation systems from immediately switching on again as soon as the frequency returns to the tolerance range specified by the connection and reconnection conditions given in 8.3, which would, at that time, put the stability of the network operation at risk, it is required to ensure a waiting period of at least 60 seconds after a switch off time of the power generation systems of more than 3 seconds To ensure uninterruptable supply of the network — in particular when the network stand-by system connects at a moment of power surplus in the low-voltage network — it is advisable to use network stand-by systems that are able to reverse power on a short-term basis.
8.3 8.3.1
Connection conditions and synchronisation General
A power generation system shall be connected to the network operator’s network only if a suitable device determines that both the mains voltage and the mains frequency are within the tolerance range of 85 % Un to 110 % Un or 47,5 Hz to 50,05 Hz, respectively, for a period of at least 60 seconds. In addition to that, the delay times for reconnection of a generator and the staggered times applicable when connecting several generators shall be chosen so that all control and adjustment processes within the power generation system caused by the connection are safely finished. If decoupling protection devices are tripped because of a short interruption (AR in the upstream mediumvoltage network or other short-time interruptions), then the power generation system is permitted to already reconnect as soon as the mains voltage and mains frequency have uninterruptedly remained within the tolerance ranges given above for a period of 5 seconds. Short-time interruptions are characterised by the NS protection settings of the mains frequency and/or network voltage being exceeded or undershot for a maximum period of 3 seconds. In the case of the power generation system being reconnected to the network operator’s network at the tripping of the decoupling protection device, the active power of controllable power generation systems supplied to the network operator’s network shall not exceed the gradient of 10 % of the active power PAmax per minute. Non-controllable power generation systems may connect after 1 minute to 10 minutes (random generator) or later. From this, it follows that it is permissible to supply with PAmax after 10 minutes. For manual operations performed on site (e.g. for the purposes of initial start-up or maintenance) it is permitted to deviate from the reconnection conditions described in this paragraph. In the case of manual disconnection of the power generation system by the network operator, the system operator is to co-ordinate reconnection with the network operator’s department responsible for the network operation. 37
VDE-AR-N 4105:2011 (E)
8.3.2
Connection of synchronous generators
A synchronisation device shall be provided in a suitable place for synchronous generators coupled directly to the network. While, for power generation systems not capable of isolated operation, the synchronisation device is, for practical reasons, assigned to the generator switch, a synchronisation device should in addition be provided at the interface switch for power generation systems that are capable of isolated operation. An automatic parallel connection device is to be provided. The setting values shall be co-ordinated with the network operator. The following values may be considered to be common maximum values: –
Δϕ = ± 10°;
–
Δf = ± 500 mHz;
–
ΔU = ± 10 % Un.
Depending on the ratio of network short-circuit power to generator power it may be necessary to establish narrower limits to avoid inadmissible system reactions at the moment of connection. 8.3.3
Connection of asynchronous generators
For asynchronous generators started by a prime mover and connected at a rotational speed between 95 % and 105 % of the synchronous rotational speed, kimax is expected to be = 4. For asynchronous generators, which are not connected dead, the connection conditions specified for synchronous generators shall be satisfied. 8.3.4
Connection of power generation units with inverters
Power generation units with inverters (such as photovoltaic systems) shall only be connected with kimax ≤ 1.
8.4
Reactive power compensation
Equipment for reactive power compensation shall either: –
be connected or disconnected together with the consumption devices or power generation systems; or
–
operated via control equipment.
Necessity and type of detuning shall be agreed upon between system operator and network operator. NOTE
9 9.1
Provisions in analogy to TAB 2007 [3].
Verification of the electrical properties General
For every power generation system, a type-specific certificate of conformity in accordance with G.2 is required. This certificate of conformity shows the electrical properties of the power generation unit in order to demonstrate its conformity with the requirements of this VDE application guide. In addition to that, a type-specific certificate of conformity in accordance with G.3 shall be submitted to the network operator for the network protection and system protection confirming the protective functions and the protection settings of this VDE application guide. The certificates of conformity issued for the power generation units and the NS protection shall confirm their conformity with the requirements of this VDE application guide at least with regard to the properties described in 9.2 to 9.4. For this, the following properties shall be verified by measurement. Until such time when a test
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specification is available, the conformity shall be verified in accordance with Clauses G.2 and F.3 for power generation units and Clauses G.3 and F.4 for the NS protection.
9.2 9.2.1
Verification of the feed-in power Verification of the feed-in active power
For power generation units, it is sufficient to indicate the maximum active power feed-in. 9.2.2
Verification of the reactive power values
Indication of the maximum reactive powers for inductive (under-excited) and maximum capacitive (overexcited) reactive power extraction as a function of the feed-in active power is required. For this, at least the conditions given in 5.7.5 shall be satisfied. In order to check for compliance with the firmly predefined displacement factor cos ϕ, it shall be verified by measurement in the course of type testing that the default displacement factor given for the system control is actually complied with at the terminals of the power generation unit (maximum deviation for cos ϕ: less than 0,01). For power generations units with a generator directly coupled to the network which, due its very operational principle, cannot control the reactive power and, therefore, uses non-controllable, fixed capacities (such as an asynchronous generator) cos ϕ shall be reached within 60 seconds. The maximum deviation for cos ϕ at nominal voltage shall be 0,02. 9.2.3
Verification of the reactive power transition function
In order to check the standard characteristic curve cos ϕ (P) given in 5.7.5, the change of the reactive power mode of operation is to be checked in correspondence to the magnitude of the active power feed-in. To this end, the active power range of the power generation unit shall be run through three times from minimum to maximum active power feed-in and vice versa in steps of 10 % of the nominal power more and, based on that, the magnitude of the displacement factor cos ϕ and the transient period shall be indicated. As a minimum, the conditions given in 5.7.5 shall be satisfied.
9.3
Verification of the network reactions
In order to verify the permissible network reactions specified in 5.4, it is required to submit evidence provided by the manufacturer (see the forms given in G.2 and F.3) for the radiated interference produced by the power generation unit. This applies to all power generation units in general, because in the case of several possibly smaller power generation units being interconnected the sum current of all power generation units can exceed 75 A which would require the network reactions to be calculated.
9.4
Verification of the features of the network and system protection
Compliance with the conditions required by Clause 6 for NS protection (such as setting values and disconnection times) for the protection against inadmissible voltage and frequency increase/decrease shall be verified based on measurements (see the forms given in G.3 and F.4). For integrated NS protection, the functional chain “NS protection — interface switch” shall be checked. Islanding detection shall be verified in accordance with 6.5.3.
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Annex A (informative) Explanations A.1
“Power generation system” (3.1.8) and “power generation unit” (3.1.9)
Figure A.1 shows the power generation system, the power generation unit and the sum of all power generation systems connected to the same network connection point.
Figure A.1 — Overview on the concepts of power generation unit and power generation system
A.2
Permissible voltage change (5.3)
The operation of power generation systems changes the operating voltage of the network. The voltage change at the PCC for the extraction of inductive reactive power can be expressed as follows:
Δua =
40
S Amax ⋅ (RkV ⋅ cos ϕ − X kV ⋅ sin ϕ ) U2
(A.1)
VDE-AR-N 4105:2011 (E)
As shown by equation (A.1), the voltage change may become negative, if the first term in the numerator becomes smaller than the second one, which is possible when cos ϕ is sufficiently small, hence, if there is a sufficiently high extraction of inductive reactive power. For the extraction of capacitive reactive power:
S ⋅ (RkV ⋅ cos ϕ + X kV ⋅ sin ϕ ) Δua = Amax U2
(A.2)
This equation shows that the extraction of capacitive reactive power adds to the voltage increase which is to be taken into consideration for variable reactive power extraction. Equations (A.1) and (A.2) are practicable approximations. The voltage changes calculated by means of these equations are slightly larger than the more exact results of a complex load-flow analysis.
A.3
System reactions (5.4)
A.3.1
Rapid voltage changes
The factor kimax is referred to as the maximum switching current factor and indicates the ratio of the highest current occurring during the switching operation gives (e.g. a starting current Ia) to the nominal current of the power generation system; for example: kimax =
Ia InG
(A.3)
Results obtained from a calculation using this maximum switching current factor represent an upper estimate and are therefore, as a matter of principle, on the safe side. Values for this factor shall be gathered from the certificate of conformity. If the maximum switching current factor kimax is not calculated using equation (A.3), then the following reference values may be used: –
kimax = 1,2
–
kimax = 4 for asynchronous generators, which are connected at 95 % to 105 % of their synchronous rotational speed if no further details are available as to the type of current limitation.
for synchronous generators with fine synchronisation, inverters;
With regard to short-term transient phenomena, the condition mentioned below shall be adhered to for very short voltage changes; –
kimax = 8 unknown.
for asynchronous generators, which are started from the network by means of motors if Ia is
Rapid voltage changes can be calculated more accurately than with equation (3) if the feed-in and network angles are taken into consideration: Δu = kimax
SrE ⋅ cos (ψ + ϕ ) SkV
(A.4)
Where: ⎛X is the network impedance angle ψ = arctan ⎜⎜ kV ⎝ RkV
ϕ
⎞ ⎟ ⎟ ⎠
is the displacement factor of the power generation system
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The displacement factor ϕ shall be positive for under-excited generator operation and negative for overexcited generator operation. Even if asynchronous machines or smaller synchronous generators without fine-step synchronisation are connected to the network with an approximately synchronous rotational speed, there may be very short voltage changes as a result of internal transient phenomena. Such a voltage change is permitted to be two times the otherwise applicable value, i.e. 6 %, provided that it is no longer than two full oscillations and that the voltage change following it does not exceed 3 % of the voltage measured initially before connection of the asynchronous machine. Coincidence of switching operations of several generators connected to the same PCC leads to a multiple of the voltage change caused by a single generator and is to be avoided, if the maximum voltage change exceeds 3 % in total. One possible way that is suitable in terms of technology is to stagger the individual switching operations. With that, the intervals between two switching operations are determined by the magnitude of the voltage changes caused by them and they shall be at least 10 minutes for the maximum permissible apparent generator power. In case of a nominal generator power of less than half the permitted value, an interval of one minute is sufficient.
A.3.2
Flicker
According to 5.4.3, flicker is deemed to be sufficiently limited for power generation systems with rated currents of up to 75 A, if the limit values of DIN EN 61000-3-3 (VDE 0838-3) or DIN EN 61000-3-11 (VDE 0838-11) are complied with. If the limit values of DIN EN 61000-3-3 (VDE 0838-3) are not complied with at the reference impedance Zref, connection may still be permissible, according to DIN EN 61000-3-11 (VDE 0838-11), if the amount of the impedance of the supply network at the connection point shared with the public network is less than the amount of the maximum permissible network impedance Zmax determined in accordance with DIN EN 61000-3-11 (VDE 0838-11). In order to perform this comparison, the network impedance shall be determined at the connection point and compared with the value Zmax gathered from the device documents. The connection owner provides the network operator with the necessary values from the device documents of the manufacturer. For power generation systems with several power generation units, Plti shall be calculated separately for each individual power generation unit and, using this value, a resulting value for the flicker interference factor at the PCC shall be obtained using the following equation: Plt res =
∑ Plt2i
(A.5)
i
For a power generation system consisting of n identical power generation units, the resulting value for the flicker interference factor is: Plt res = n ⋅ Plt E
A.3.3 A.3.3.1
(A.6)
Harmonics and inter-harmonics General
When calculating the permissible harmonic currents care shall be taken not to apply the rated short-circuit power of the low voltage network but the actual network short-circuit power SkV at the PCC. For the superposition of the harmonic currents of certain inverter types, the type specific rules listed in the following apply.
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A.3.3.2
Line-commutated inverters (six- or 12-pulse)
The inverter-typical harmonic currents (of 5th order, 7th order, 11th order, 13th order, etc.) as well as non-typical ones of very low order (ν < 13) are added up arithmetically: n
∑ Iνi
Iν =
(A.7)
i =1
For the non-typical harmonics of higher order (ν ≥ 13), the total harmonic current of an order equals the root of the sum of squares of the harmonic currents of this order: n
∑ Iνi2
Iν =
A.3.3.3
(A.8)
i =1
Pulse-modulated inverters
For an ordinal number μ which is, in principle, non-integral but also includes integral values for values of μ ≥ 13, the total current equals the root of the sum of squares of the currents of the power generation units: n
∑ I μi2
Iμ =
(A.9)
i =1
If untypical harmonic currents occur with such inverters for integral ordinal numbers of ν < 13, these currents shall be added up arithmetically in correspondence to equation (A.7). Harmonic currents above 2nd order as well as inter-harmonics may be calculated using equation (A.9), if the pulse frequency of the inverter is at least 1 kHz. If several power generation units/power generation systems are effective at the same PCC, then the harmonic currents permissible for an individual power generation unit/power generation system are calculated from the apparent power SAimax of the power generation unit/power generation system i and the feed-in power connectable or planned SAV at this PCC as follows: –
for arithmetical addition of the harmonic currents, using equation (A.7):
Iν –
A izul
= Iν
zul
⋅
S A i max S AV
(A.10)
for square addition of the harmonic currents using equation (A.8) and equation (A.9):
Iν
A izul
= Iν
zul
⋅
S A i max S AV
(A.11)
Under special circumstances, harmonics of higher frequency (i.e. within a range above 1 250 Hz) may occur, which are attributable to the fact that weakly damped resonances of sub-networks are excited by commutation notches. In such a case, particular measures shall be taken which are described in greater detail in Technische Regeln zur Beurteilung von Netzrückwirkungen (Technical rules for evaluation of network reactions).
A.4
Connection criteria (5.5)
Table A.1 shows the possible variants of feed-in and protection as determined by the maximum apparent power of the power generation system SAmax.
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Table A.1 — Implementation of the connection criteria after 5.5
Feed-in Protection
EA ≤ 13,8 kVA
13,8 ≤ EA ≤ 30 kVA
EA > 30 kVA
Single-phase or threephase current
Three-phase current
Three-phase current
Integrated NS protection with U> = 1,1 Un
Central NS protection with U> = 1,1 Un
or
or
Central NS protection with U> = 1,1 Un
Central NS protection with U> = 1,1 Un
or
and
Central NS protection with U> = 1,1 Un
Integrated NS protection with U> = 1,1 … 1,15 Un
and Integrated NS protection with U> = 1,1 … 1,15 Un
A.5
Reactive power (5.7.5)
For power generation units, the reactive power control serves to better integrate the power generation systems into the low-voltage network. It provides an important contribution to the efficient use of available network capacities. Along with the properties of the power generation system (fluctuating or constant feed-in), it is also required to take into account the respective network conditions in order to achieve optimum usage. In a network in which the feed-in power is limited by the voltage criterion (typically line taps), the voltage stability can be optimised by under-excited operation of the power generation system (Figure A.2).
Figure A.2 — Potential for optimisation provided by a suitable reactive power feed-in for typical overhead line or cable types (related to an operation mode where cos ϕ = 1)
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The bandwidth takes into account an under-excited operation mode between cos ϕ = 0,9 and cos ϕ = 1, typical local network transformers as well as the distance of the power generation system to the local network transformer. Due to their lower R/X ratio, the potential for optimisation is generally larger for overhead lines than it is for cables. Even for great distances from the local network transformer, there are considerable effects on the mains voltage when using a suitable reactive power control. However, it shall be noted that the reactive power control comes along with a greater power loss in the lowvoltage network. This power loss can be minimised using a characteristic curve cos ϕ (P). When doing so, the power generation system is operated in an under-excited mode only, if it feeds with nearly rated power. Because of this behaviour, the characteristic curve cos ϕ (P) is suitable for power generation systems with fluctuating power feed-in, such as PV systems. The network operator may provide different characteristic curves for the power generation system’s reactive power operation mode depending on the network conditions. In general, the prescribed characteristic curve cos ϕ (P) has two, however, not more than four nodes (cf. Figure A.3). Characteristic curve cos ϕ (P)
*)
Depending on SAmax.
Key Standard characteristic curve Variant of the characteristic curve Figure A.3 — Examples of a characteristic curve cos ϕ (P) with three nodes Starting with a power of 0,2 PEmax, the characteristic curve shall be adhered to. The reactive power operation mode used to ensure static voltage stability in the networks is a new requirement for power generation systems and requires further consideration in particular for reactive energy clearing and for the use of reactive current compensation systems.
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VDE-AR-N 4105:2011 (E)
For full feed-in of the power generation system, the network operator will, in general, require an the power generation system to operate in an under-excited mode above 0,5 Pn (also see the standard characteristic curve cos ϕ (P) in Figure 4). For excess feeding the use of an “intelligent” reactive current compensation system is required which, depending on the overall behaviour of the customer system for extraction or feed-in, regulates the displacement factor cos ϕ respectively required for the entire customer system at the network connection point. As long as the required reactive current compensation systems are not commercially available, it is advisable to use a differentiated approach when specifying the displacement factor cos ϕ of the power generation system. In the case of the greater part of the generated power being supplied to the network operator’s network and for a feed-in power of more than approx. one third of the maximum extraction power agreed, a displacement factor cos ϕ in the range from 0,90under-excited to 0,95under-excited is normally to be set in accordance with the network operator’s provisions. If a reactive current compensation system regulates in relation to cos ϕ at the network connection point, then the predefined value shall be set at the reactive current compensation system. The power generation system may be set to cos ϕ = 1. If cos ϕ is regulated only in correspondence to the extraction customer part of the customer system, then the power generation system shall be set to the value of cos ϕ provided by the network operator. More detailed information on the power ratio can be obtained by network calculations examining the effects that the different load cases of the customer system have on the voltage change at the network connection point. In cases where the feed-in power is less than one third of the maximum extraction power agreed, a specific default for the displacement factor of the power generation system is normally not required. For minimisation of the losses in the entire system, a displacement factor of cos ϕ = 1 shall be aimed for. If a reactive energy clearing is applied that is influenced by the power generation system, then the network operator and the system operator should always coordinate their procedures for a reactive power compensation of the customer system and for the default displacement factor for the power generation system. It may also be sensible to use a reactive energy meter (e.g. load- profile meter) for the power generation system and, for balancing purposes, to take into account the entire supply point for the customer system.
A.6
General requirements, single-fault tolerance (6.1)
The central NS protection, integrated NS protection, integrated interface switch as well as the trigger circuit consisting of the integrated NS protection and integrated interface switch shall meet the requirements for single-fault tolerance. Taking into account the basic safety principles, these devices shall be designed, constructed, chosen, assembled and combined at least so that they can withstand the operating conditions to be expected (e.g. reliability with regard to their breaking capacity and switching frequency) as well as the external influences to be expected (e.g. mechanical vibration, external fields, interruptions or disturbances of the energy supply). A single fault shall not lead to a loss of the safety function. Faults of common cause shall be taken into account if the probability for the occurrence of such a fault is significance. Whenever reasonably practical, the individual fault shall be displayed and lead to the power generation unit or system being disconnected. NOTE 1 This requirement for the detection of individual faults does not mean that all faults are detected. Accumulation of undetected faults can therefore lead to an unintentional output signal and to a hazardous state. NOTE 2
This system allows for:
–
the safety to always be maintained in the event of a single fault;
–
some but not all faults o be detected;
–
the accumulation of undetected faults to possibly lead to the loss of the safety functions.
NOTE 3 Further explanation of the term “single-fault tolerance”: For implementation of the single-fault tolerance, all the units required for the protective functions in the devices are executed so that, in the event of a fault occurring (e.g.
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VDE-AR-N 4105:2011 (E)
malfunctioning of a processor or measurement amplifier), this malfunction is detected by another unit and leads to disconnection.
Independent of each other, the series-connected switches shall have a breaking capacity corresponding to the rated current of the power generation system. At least one switch shall be executed as a power relay or contactor and be suitable for overvoltage category 2. For single-phase feed-in systems, the switch shall have one contact of this overvoltage category each for both the neutral conductor and the line conductor. For polyphase supply systems, it is required to have one contact of this overvoltage category each for all active conductors. The second switch may be formed by the electronic switching components of the inverter bridge or another circuit provided that the electronic switching components can be disconnected by control signals and that it is ensured that a failure is detected and leads to prevention of the operation at the latest at the next reconnection. For inverters without simple separation between network and PV generator (inverters without transformers), both the switches mentioned in the paragraph above shall be executed as power relays, contactors or mechanical circuit-breakers with the requirements described therein, although a disconnection device is permitted to be connected between PV generator and inverter.
A.7
Interface switch (6.4)
All-phase switching means switching all active conductors of the power generation system from the feed-in point to the customer system or from the network operator’s network (depending on the interface switch mounting place). DIN VDE 0100-200 (VDE 0100-200) defines active conductors as all conductors intended to be live under normal operating conditions and includes the neutral conductor. By agreement, PEN conductors are excluded. DIN VDE 0100-460 (VDE 0100-460) defines the conductors to be switched. Depending on the network system at the interface switch mounting place, the following requirements arise. In the TT system, the three line conductors and the neutral conductor shall be connected. In the TN-C system and in the TN-C part of the TN-C-S system, the three line conductors shall be connected. In the TN-S system and in the TN-S part of the TN-C-S system, the three line conductors and the neutral conductor shall be connected. This means that, with the exception of the conductors with a PE function, all conductors shall be connected. If connection of the neutral conductor is required, then a interface switch shall be used which connects the neutral conductor with phase-lead at turn-on and phase-lag at turn-off, however, at least simultaneously.
A.8 A.8.1
Protective devices for the interface switch (6.5) General
With regard to the proper protection of the power generation system, it shall be considered that the shortcircuit current is considerably lower for island mode than for network parallel operation. For power generation systems feeding into the low-voltage network via inverters, it may even be less than the system’s rated current. The use of residual current devices (RCD) may be inevitable.
A.8.2
Protective functions
Should operational problems occur for existing systems in the context of the protective functions required by the now obsolete VDEW directive „Eigenerzeugungsanlagen am Niederspannungsnetz“ (Power generation systems connected to the low-voltage network) (such as problems with the net impedance measurement hitherto applied), the existing system may be retrofitted following the provisions of this VDE application guide.
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Annex B (informative) Connection examples B.1
Maximum apparent connection power SAmax ≤ 4,6 kVA
*) RCD required in the TT system or in accordance with, e.g., DIN VDE 0100-410 (VDE 0100-410) and DIN VDE 0100-712 (VDE 0100-721), respectively. Figure B.1 — Connection of a single-phase power generation unit with full feed-in and a maximum apparent connection power ≤ 4,6 kVA
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VDE-AR-N 4105:2011 (E)
B.2
Maximum apparent connection power SAmax ≤ 13,8 kVA
*) RCD required in the TT system or in accordance with, e.g., DIN VDE 0100-410 (VDE 0100-410) and DIN VDE 0100-712 (VDE 0100-721), respectively. Figure B.2 — Connection of 3 single-phase power generation units with full feed-in and a maximum apparent connection power ≤ 4,6 kVA per line conductor
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B.3
Power generation system with communicative coupling of the single-phase inverters and with integrated NS protection
*) RCD required in the TT system or in accordance with, e.g., DIN VDE 0100-410 (VDE 0100-410) and DIN VDE 0100-712 (VDE 0100-721), respectively. Figure B.3 — Connection of 3 single-phase power generation units in full feed-in and with communicative coupling
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B.4
Maximum apparent connection power of SAmax > 30 kVA
*) RCD required in the TT system or in accordance with, e.g., DIN VDE 0100-410 (VDE 0100-410) and DIN VDE 0100-712 (VDE 0100-721), respectively. NOTE Co-ordination with the network operator is required with regard to the meter panel execution for system sizes with operating currents > 6 A.
a)
direct measurement
b)
half-indirect measurement Figure B.4 — Connection of 3 three-phase power generation units with full feed-in
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VDE-AR-N 4105:2011 (E)
B.5
New power generation unit connected in parallel to an existing system SAmax > 30 kVA
*) RCD required in the TT system or in accordance with, e.g., DIN VDE 0100-410 (VDE 0100-410) and DIN VDE 0100-712 (VDE 0100-721), respectively. Figure B.5 — Connection of a new power generation unit connected in parallel to an existing system with full feed-in for a maximum apparent connection power SAmax > 30 kVA
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VDE-AR-N 4105:2011 (E)
B.6
Connection with meter column
*) RCD required in the TT system or in accordance with, e.g., DIN VDE 0100-410 (VDE 0100-410) and DIN VDE 0100-712 (VDE 0100-721), respectively. NOTE Co-ordination with the network operator is required with regard to the meter panel execution for system sizes with operating currents > 63 A.
a)
direct measurement
b)
half-indirect measurement Figure B.6 — Connection of a power generation system with meter column for a maximum apparent connection power SAmax > 30 kVA
53
VDE-AR-N 4105:2011 (E)
B.7
Connection for excess feed-in (self consumption in accordance with EEG, § 33 EEG and KWK-G, § 4 (3))
*) RCD required in the TT system or in accordance with, e.g., DIN VDE 0100-410 (VDE 0100-410) and DIN VDE 0100-712 (VDE 0100-721), respectively. Figure B.7 — Connection of a power generation system with excess feed-in (taking into account self consumption in accordance with EEG, § 33 and KWK-G, § 4 (3))
54
VDE-AR-N 4105:2011 (E)
B.8
Connection for excess feed-in of > 30 kVA
*) RCD required in the TT system or in accordance with, e.g., DIN VDE 0100-410 (VDE 0100-410) and DIN VDE 0100-712 (VDE 0100-721), respectively. NOTE Co-ordination with the network operator is required with regard to the meter panel execution for system sizes with operating currents > 63 A.
a)
direct measurement
b)
half-indirect measurement Figure B.8 — Connection of a power generation system with excess feed-in for a maximum connection power SAmax > 30 kVA
55
VDE-AR-N 4105:2011 (E)
Annex C (informative) Examples of meter panel configurations C.1
Meter panel for connection of a power generation system with a maximum apparent connection power SAmax ≤ 30 kVA (full feed-in)
*) RCD required in the TT system or in accordance with, e.g., DIN VDE 0100-410 (VDE 0100-410), respectively. **) Selective overcurrent protective device in accordance with TAB 2007, 7.4 required for full feed-in only. Figure C.1 — TAB meter panel: general system and power generation system ≤ 30 kVA NOTE 1
For NS protection (also see 6.1):
For a maximum apparent connection power SAmax ≤ 30 kVA, the NS protection may be integrated in the system control of the power generation units (integrated NS protection). NOTE 2
For the interface switch (also see 6.4.2):
For power generation systems with inverters, the interface switch may be provided on the inverter’s network side. A short circuit in the inverter shall not affect the interface switch in its breaking function.
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VDE-AR-N 4105:2011 (E)
C.2
*)
Meter panel for the connection of a power generation system with a maximum apparent connection power SAmax > 30 kVA and with central NS protection
RCD required in the TT system or in accordance with DIN VDE 0100-410 (VDE 0100-410), respectively.
**) Selective overcurrent protective device in accordance with TAB 2007, 7.4 required for full feed-in only. ***) The ball switch may also be inserted decentralised at or in the power generation system. Figure C.2 — TAB meter cabinet: general system and power generation system > 30 kVA NOTE 1
For NS protection (also see 6.1):
The NS protection is to be implemented as central NS protection at the meter panel. NOTE 2
For the interface switch (also see 6.4.2):
The two break devices of the interface switch are to be installed in the circuit distributor of the power generation system adjacent to the meter panel.
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VDE-AR-N 4105:2011 (E)
C.3
*)
Meter panel for the connection of a power generation system that includes transformer measurement
RCD required in the TT system or in accordance with DIN VDE 0100-410 (VDE 0100-410), respectively.
**) The ball switch may also be inserted decentralised at or in the power generation system. Figure C.3 — Meter panel for the connection of a power generation system that includes transformer measurement NOTE 1
For NS protection (also see 6.1):
The NS protection is to be implemented as central NS protection at the meter panel. NOTE 2
For the interface switch (also see 6.4.2):
The two break devices of the interface switch are to be installed in the circuit distributor of the power generation system adjacent to the meter panel.
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VDE-AR-N 4105:2011 (E)
C.4
Meter panel (that may also be arranged in a decentralised manner) for the connection of a power generation system for self consumption or excess feed-in in accordance with EEG, § 33 and KWK-G, § 4
C.4.1
*)
General
RCD required in the TT system or in accordance with DIN VDE 0100-410 (VDE 0100-410), respectively. Figure C.4 — Meter panel (that may also be arranged in a decentralised manner) for the connection of a power generation system for self consumption or excess feed-in
NOTE 1
For NS protection (also see 6.1):
The NS protection may be integrated in the system control of the power generation units (integrated NS protection) for a maximum apparent connection power SAmax ≤ 30 kVA. NOTE 2
For the interface switch (also see 6.4.2):
For power generation systems with inverters, the interface switch may be provided on the inverter’s network side. A short circuit in the inverter shall not affect the interface switch in its breaking function.
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VDE-AR-N 4105:2011 (E)
C.4.2
Schematic representation
Figure C.5 — Measuring principle for the implementation of EEG 2009, § 33 (2) or KWK-G 2009, § 4 (3a)
C.4.3
Organisation of a central meter panel
Figure C.6 and Figure C.7 show variants for the metering and meter panel organisation that are suitable for implementation of EEG 2009, § 33 (2) or KWK-G 2009, § 4 (3a) taking into consideration „Technische Anschlussbedingungen für den Anschluss an das Niederspannungsnetz“ (Technical connection conditions for connections to the low-voltage network (TAB 2007) [3]) for conventional meter panels (three-point fastening) and meter panels with integrated fastening and contacting devices (BKE-I).
Figure C.6 — Connection variant for a central conventional meter panel with three-point fastening
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VDE-AR-N 4105:2011 (E)
Figure C.7 — Connection variant for a central eHZ meter panel with BKE-I
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VDE-AR-N 4105:2011 (E)
Annex D (normative) Islanding detection D.1
Islanding detection by means of the oscillating circuit test
Test circuit The inverter is supplied by a suitable voltage source. For power generation units without inverters, the energy supply is ensured by a suitable drive mechanism. Downstream of the inverter, resistors, reactors and capacitors are switched parallel to the output, which form an RLC oscillating circuit and can be adjusted in very small steps to the generated active and reactive powers (Figure D.1). Both RLC oscillating circuit and power generation unit shall be connected via separate switches to the network or to a suitable network simulator. This oscillating circuit shall have a quality factor Q of at least 2. The active power input of the oscillating circuit shall equal the active power output of the power generation unit or the inverter, respectively, to within ± 3 %. For nominal voltage, the total harmonic distortion factor of the reactor current shall be less than 3 %. With that, the following relationships apply to the setting of inductance and capacity: L=
U2 2π ⋅ f ⋅ P ⋅ Q
C=
P⋅Q 2π ⋅ f ⋅ U 2
(D.1)
Where U is the mains voltage, f is the mains frequency and P is the active power supplied by the power generation unit.
Figure D.1 — Example with integrated NS protection in the inverter Test sequence The sequence of the test is as follows: 1)
By means of the voltage source or, in the case of power generation units without inverters, a suitable drive mechanism, the power of the power generation unit to be tested is defined.
2)
The power generation unit is connected to the network or the network simulator, respectively, by closing S3 and S2. With the oscillating circuit not connected (S1 opened), the active power (P) and the reactive power (Q) flowing into the network from the power generation unit are now measured.
3)
The power generation unit is separated from the network (S2 open).
4)
The oscillating circuit is tuned as follows:
62
a)
The inductance is adjusted correspondingly, so that Q > 2.
b)
The capacity is adjusted correspondingly, so that PQC + PQL = −PQ,WR.
c)
The resistance is adjusted so that the active power absorbed by the entire oscillating circuit equals P.
VDE-AR-N 4105:2011 (E)
d)
The oscillating circuit and power generation unit are connected with the network (S1, S2 and S3 closed) and, following this, the power generation unit is put into operation.
NOTE The purpose of tuning is to minimise the fundamental component of the current over S3 as far as possible. Through fine tuning of the oscillating circuit (step 6)), the most unfavourable conditions shall be established with respect to a possible island effect.
5)
In order to start the test, S3 is opened and the time until disconnection of the power generation unit is measured.
6)
After every successful test, one parameter (L or C) is changed by approx. 1 % within a total range of ± 5 % and the test is repeated.
The full test sequence shall be carried out at P = 25 %, 50 % and 100 % of the rated power respectively. The complete test is deemed to have been passed if the disconnection times of every individual test are shorter than 5 seconds. The test shall be carried out at nominal frequency ± 0,1 Hz and nominal voltage ± 3 %. For the purpose of testing a three-phase disconnection device, a test circuit is connected successively to one of the line conductors as shown in Figure D.1. Each time, the two remaining line conductors are directly connected to the network. The disconnections shall respectively occur within 5 seconds after opening the switch S.
D.2
Islanding detection by three-phase voltage monitoring
If at least one line conductor voltage falls below the limit values of 80 % or exceeds 115 %, automatic disconnection shall follow within 0,2 seconds. Here, too, the requirements with regard to functional safety given in A.6 of this VDE application guide shall be satisfied. For the purpose of checking the voltage monitoring, the power generation unit shall be operated via an alternating voltage source of variable amplitude at nominal voltage and with arbitrarily chosen power. The disconnection time shall be maintained at test voltage steps from 100 % Un to 118 % Un and from 100 % Un to 77 % Un. This test shall be carried out for all line conductor combinations. NOTE The three-phase voltage monitoring is permissible even for structural integration of several singlephase power generation units feeding into different line conductors validly, as long as the currents of these power generation units are regulated independent of each other so that arbitrary phase relationships can develop.
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VDE-AR-N 4105:2011 (E)
Annex E (informative) Examples for the connection evaluation of power generation systems E.1
Connection of a 20 kW photovoltaic system
Data of the power generation system
Figure E.1 — Power generation unit (sketch of the set-up and connections) Strategy (principle, inverter strategy): –
1 central inverter connected to the low-voltage network via a meter port column;
–
inverter with integrated NS protection.
Power generation system (data were taken from the data sheet) Low-voltage side network of the power generation system Total cable length:
50 m
Type, cross-section of the cable:
NAYY-J 4 ⋅ 35 mm2
Network data
Figure E.2 — Network (sketch) Short-circuit power of the upstream network:
SK,MS = 100 MVA
Local network transformer:
Sr Tr = 400 kVA
uk = 4 %
Cable NAYY-J 4 × 95:
R’ = 0,32 Ω/km
X’ = 0,082 Ω/km
Overhead line Al 70:
R’ = 0,436 Ω/km
X’ = 0,309 Ω/km
64
PCu = 4,6 kW
VDE-AR-N 4105:2011 (E)
Calculation of the network short-circuit power of SkV at the network connection point –
Impedances of the 20 kV network SkVN = 100 MVA R/X = 0,5 ZN =
400 V × 400 V U2 = = 1,6 m Ω 100 MVA SkVN
(E.1)
with R/X = 0,5 RN =
–
ZN2 = 0,72 mΩ 3
X N = 2 ⋅ RN = 1,43 mΩ
(E.2)
Impedances of the local network transformer Sr Tr = 400 kVA, uk = 4 % S SkT = r = 10 MVA uk
ZT =
U2 = 16 mΩ SkT
(E.3)
The resistance of the local network transformer can be calculated from the short-circuit losses of the local network transformer. –
Short-circuit losses PCu = 4,6 kW PCu = 3 ⋅ Ir 2 ⋅ RT = 3 ⋅ U2
RT =
Sr 2
Sr 2
3 ⋅U2
⋅ RT
(E.4)
⋅ PCu = 4,6 mΩ
X T = Z T 2 − RT 2 = 15,3 mΩ
–
Impedances of the cable, length:
200 m
–
Reactance per unit length of the cable:
0,082 Ω/km
–
Resistance load per unit length of the cable:
0,32 Ω/km
XL = 16,4 mΩ
RL = 64 mΩ
–
Impedances of the overhead line, length:
300 m
–
Reactance per unit length of the overhead line:
0,309 Ω/km
–
Resistance load per unit length of the overhead line:
0,436 Ω/km
XL = 92,7 mΩ
RL = 130,8 mΩ
(E.5)
(E.6)
(E.7)
The impedances relevant for the connection of the system result from the sum of the following individual values
XkV = 125,8 mΩ
RkV = 200,1 mΩ
ZkV = 236,4 mΩ
(E.8)
and the short-circuit power SkV =
U2 ⋅ 676,8 kVA ZkV
(E.9)
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VDE-AR-N 4105:2011 (E)
Specifications of the network operator with regard to the network connection In order to ensure optimum network loading, all new power generation systems are required to participate in the static voltage stability. Static voltage stability shall be ensured with the standard characteristic curve cos ϕ (P) given in 5.7.5. To this end, the power generation system shall allow to be operated so, that the displacement factor can be set in the range of: 0,9under-excited ≤ cos ϕ ≤ 1
(E.10)
On the outgoing feeder, a 10 kW photovoltaic system (cos ϕ = 1) is already available. On the other outgoing feeders of the local network transformer, a total feed-in power of 35 kW (cos ϕ = 1) is connected. Check of the permissible voltage change specified in 5.3 Since the photovoltaic system is operated with a characteristic curve cos ϕ (P), a displacement factor of cos ϕ = 0,90under-excited shall be assumed for the maximum apparent power of the power generation system. A displacement factor cos ϕ = 1 results in a voltage change at the PCC of the PV system of: Δua =
S Amax ⋅ (RkV ⋅ cos ϕ − X kV ⋅ sin ϕ ) U
2
=
20 kW ⋅ (200,1 m Ω ∗ 1)
(400 V )2
= 2,5 %
(E.11)
The maximum apparent power of the power generation system is obtained when using a displacement factor cos ϕ = 0,90under-excited. According to equation (A.1), under-excited operation yields a voltage change at the PCC of the PV system of: Δua =
S Amax ⋅ (RkV ⋅ cos ϕ − X kV ⋅ sin ϕ ) U
2
=
22,2 kVA ⋅ (200,1 mΩ ⋅ 0,9 − 125,8 m Ω ⋅ 0,44 )
(400 V )2
= 1,73 %
(E.12)
When taking into consideration the power generation systems already in existence and the planned photovoltaic system, superposition of the voltage changes of the systems results in a voltage change as shown in Table E.1. Table E.1 — Voltage change at the individual PCCs Voltage change in % VP ON transformer
VP PVold
VP PVnew
EA 35 kW (cos ϕ = 1)
0,12
0,12
0,12
PVold (cos ϕ = 1)
0,03
0,43
0,43
-0,04
0,66
1,73
0,11
1,21
2,28
PVnew (0,90under-excited) Sum
That leads to a voltage increase of at maximum 2,28 %. It is to be checked, whether the predefined standard characteristic curve cos ϕ (P) can be used without modifications. To this end, the maximum voltage increase of the power generation system is set as the limit and the maximum feed-in power, PAmax, that is possible for this limit value is calculated for the respective displacement factors cos ϕ = 1, cos ϕ = 0,9over-excited and cos ϕ = 0,9under-excited.
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VDE-AR-N 4105:2011 (E)
PAmax =
(RkV
cos ϕ ⋅ Δua ⋅ U 2 0,017 3 ⋅ (400 V )2 = = 13,8 kW ⋅ cos ϕ − X kV ⋅ sin ϕ ) 200,1 mΩ
(E.13)
This leads to the following points on the characteristic curve: Table E.2 — Voltage change at the individual PCCs (with the characteristic cos ϕ (P)) cos ϕ (PV system only)
Voltage change sum (only PVnew) in % VP ON transformer
VP PVold
VP PVnew
PAmax/kW
0,90under-excited
0,11 (−0,04)
1,21 (0,66)
2,28 (1,73)
20
0,95under-excited
0,15 (0,00)
1,19 (0,64)
2,28 (1,73)
17,4
1
0,20 (0,05)
1,15 (0,60)
2,28 (1,73)
13,8
The resulting characteristic curve is on the safe side, when compared to the predefined standard characteristic curve, which means that the standard characteristic curve leads to a smaller voltage increase. Therefore, the predefined standard characteristic curve can be used. Verification of the rating of the electrical equipment in accordance with 5.2
Constant current load The maximum apparent power results from the maximum active power and the predefined displacement factor cos ϕ: 20 kW P S Amax = Emax = = 22,2 kVA cos ϕ 0,9
(E.14)
The maximum feed-in current resulting at the nominal network voltage of 400 V is: I Amax =
S Amax ( 3 ⋅ 400 V )
=
22,2 kVA ( 3 ⋅ 400 V )
= 32,1 A
(E.15)
The maximum fed-in currents are far below the permitted constant current load capacity of the electrical equipment. Short-circuit current The new photovoltaic system delivers a short-circuit current corresponding to the nominal current of ′′ PV = 32 A. Ik, The photovoltaic system raises the short-circuit current at the PCC from 977 A to 1 009 A. The rated shortcircuit current of the overhead line Al 70 is 3,8 kA. Therefore, the short-circuit rating of the electrical equipment is sufficient. Verification of the system reaction “rapid voltage change”
The rated apparent power of the inverter is given as 22,5 kVA. The value for kimax is 1,2.
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VDE-AR-N 4105:2011 (E)
Δua = kimax ⋅
22,5 kVA SrE = 1,2 ⋅ =4% 676,8 kVA SkV
(E.16)
The rapid voltage change of 4 % is outside the permitted range. Therefore, a more exact consideration is required: Δua = kimax ⋅
SrE ⋅ cos (Ψ + ϕ ) SkV
(E.17)
Where: Ψ
⎛X is the network impedance angle Ψ = arctan ⎜⎜ kV ⎝ RkV
ϕ
is the displacement factor of the power generation system (in this case: cos ϕ = 0,9under-excited). Δua = kimax ⋅
⎞ ⎟; ⎟ ⎠
22,5 kVA SrE ⋅ cos (Ψ + ϕ ) = 1,2 ⋅ ⋅ cos (32,2° + 25,8°) = 2,1 % 676,8 kVA SkV
(E.18)
With 2,1 %, the rapid voltage change is inside the permissible range. Check of the network reaction “long-term flicker”
The limit values of DIN EN 61000-3-11 (VDE 0838-11) are adhered to. Check of the network reaction “harmonics and inter-harmonics”
The limit values given in Table 2 or Table 3 of DIN EN 61000-3-12 (VDE 0838-12) were adhered to. Check of the reaction on audio-frequency centralised ripple control
Centralised ripple control is not active in the network concerned. Connection decision
Connection of the 20 kW photovoltaic system to the low-voltage network can be approved of, if the power generation system feeds with a displacement factor corresponding to the standard characteristic cos ϕ (P).
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VDE-AR-N 4105:2011 (E)
E.2
Reactive power control of a heat led CHP
Figure E.3 — Reactive power control of a heat led CHP
Voltage increase caused by CHP at cos ϕ = 1:
3,65 %
Voltage increase caused by CHP at cos ϕ = 0,9under-excited:
2,83 %
Active power extraction and feed-in
Voltage deviation at the connection point for cos ϕ = 1 without consumer load
Figure E.4 — Characteristic curve cos ϕ (P) of the CHP
Figure E.5 — Resultant characteristic curve Q(P)
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VDE-AR-N 4105:2011 (E)
Figure E.6 — Characteristic curve cos ϕ (P) of the CHP
Figure E.7 — Resultant characteristic curve Q(P)
Figure E.8 — Voltage deviation at the connection point
Figure E.9 — Loss parameter current square
Increase of the losses on the line for cos ϕ = 0,9under-excited:
10,9 %
Increase of the losses on the line for the characteristic curve cos ϕ (P):
4,7 %
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VDE-AR-N 4105:2011 (E)
Annex F (normative) Forms (mandatory) F.1
initial start-up protocol for power generation systems
Initial start-up protocol — Power generation systems, low voltage (to be completed by the system erector)
System address
System erector (Electric company)
First name, surname
_____________________________________________
Street, number
_____________________________________________
ZIP code, city
_____________________________________________
Company, place
_____________________________________________
Telephone, e-mail
_____________________________________________
Power generation system Max. apparent power SAmax
_________ kVA Max. active power PAmax
_______ kW
For PV systems: Module power/generator power PAgen (relevant for feed-in remuneration)
______ kWp
Initial start-up order completed and present? Does the completed data sheet F.2 correspond to the system set-up? Measurement for billing purposes: Have the required tests been carried out prior to and at initial start-up? Is the certificate of conformity for power generation units available? Is the certificate of conformity for the NS protection available? Setting value of the central NS protection for the rise-in-voltage protection U>
_______ Un
Setting value of the integrated NS protection for the rise-in-voltage protection U>
_______ Un
If central NS protection is available: Trigger test “Central NS protection — interface switch” passed successfully? Technical equipment for reduction of the feed-in power available and operational? Does the connection confirmation require an audio frequency suppressor? Yes No
Built-in
Test protocol available
If the power generation system is considered to be a locked electric operational facility within the meaning of the currently valid DIN VDE regulations and the accident prevention regulation BGV A3, then laymen shall enter the operational facility concerned only in the company of electrically skilled persons or electrically instructed persons. The power generation system has been erected in accordance with the conditions of the VDE application guide “Power generation systems connected to the low-voltage network” and the technical connection conditions of the network operator. In the context of handing over the system, the erector has instructed the system operator and has declared the power generation system to be operational in accordance with BGV A3 § 3 and § 5 or TRBS 1201 ready-to-operate. Initial start-up of the power generation system was carried out on: _______________________________ _________________________ Place, date
_________________________ System operator
_________________________ System erector
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VDE-AR-N 4105:2011 (E)
F.2
Data sheet for power generation systems
Data sheet — Power generation systems connected to the low-voltage network (to be completed by the connection owner; one data sheet for each power generation unit)
System address
Energy type CHP operated with: Power generation system Network feed-in
Mode of operation
First name, surname
____________________________________________
Street, number
____________________________________________
ZIP code, city
____________________________________________
Solar
Wind
Hydro
Other __________
Biogas
Natural gas
Oil
Other __________
Monovalent mode of operation Max. active power PAmax _________ kW 1-phase
2-phase
Max. apparent power SAmax ____ kVA 3-phase
Three-phase current
Island mode intended?
Yes
No
Motor powered start intended?
Yes
No
Feed-in into the network operator’s network intended (excess feed-in)?
Yes
No
Feed-in of the total amount of energy into the network operator’s network (full feed-in)?
Yes
No
Reactive power Not available Available with _______________ kVAr compensation of the Number of steps _________________ Reactive power per step _______ kVAr customer system Detuning degree or resonant frequency __________________________________
Power generation units*
Manufacturer ______________________
Type __________________________
Max. active power PEmax _________ kW
Max. apparent power SEmax ____ kVA
Nominal voltage (AC) Un _________ V
Rated current (AC) Ir ___________ A
Short-circuit current _____________ kA
Starting current Ia ______________ A
Number of identically constructed units
Own demand _______________ kVA
Inverter Inverter(s) Harmonics
Remarks
NOTE*:
72
Asynchronous generator
Self-commutated; pulse frequency: ________ kHz Currents in accordance with DIN EN 61000-3-2 (VDE 0838-2) or DIN EN 61000-3-12 (VDE 0838-12), respectively
Synchronous generator Line commutated; pulse number: ___________ In accordance with the annex enclosed
________________________________________________________________
For PV systems, details for the inverters shall be given.
VDE-AR-N 4105:2011 (E)
F.3
Requirements for the test report for power generation units
Extract from test report for unit certificate "Determination of electrical properties"
No. JJJJ - nnnn (consecutive number)
Type of system:
Manufacturer's data
____________________________________
System manufacturer: ____________________________________ ____________________________________ ____________________________________ ____________________________________
____________________
Type of system: (CHP, PV-WT, ...)
Active power (nominal power at reference conditions):
_____ kW
Rated voltage:
_____ V
Measuring period: from XXXX-XX-XX to XXXX-XX-XX Active power
kW
PEmax
Reactive power reference 10
Active power P/Pn [%]
20
30
40
50
60
70
80
90
100
max. possible cos ϕunderexcited max. possible cos ϕoverexcited Compliance of required displacement factor cos ϕ 0,900ov 0,920ov 0,940ov 0,960ov 0,980ov
Default in system control Measured value at PGU terminals
1,000
0,980un 0,960un 0,940un 0,920un 0,900un
Reactive power transfer function – Standard-cos ϕ-(P)-characteristic 10
Active power P/Pn [%] cos ϕ
20
30
40
50
60
70
80
50°
70°
85°
90
100
Conform to Standard-cos ϕ-(P)-characteristic Switching actions Making operation without default (of primary energy carrier)
ki
Worst case at switch over of generator sections Making operation at reference conditions (of primary energy carrier)
ki ki
Breaking operation at nominal power Worst-case value of all switching operations
ki kimax
Angle of network impedance ψk:
Flicker
30°
Coefficient of system flicker cψ: Harmonics Active power P/Pn [%] Harmonic number 2
0
10
20
30
40
50
60
70
80
90
100
1[%]
1[%]
1[%]
1[%]
I [%]
I [%]
1[%]
1[%]
1[%]
I [%]
I [%]
0 I [%]
10 I [%]
20 I [%]
30 I [%]
40 I [%]
50 I [%]
60 I [%]
70 I [%]
80 I [%]
90 I [%]
100 I [%]
0 I [%]
10 I [%]
20 I [%]
30 I [%]
40 I [%]
50 I [%]
60 I [%]
70 I [%]
80 I [%]
90 I [%]
100 I [%]
3 4 5 ... 40 Subharmonics Active power P/Pn [%] Frequency [Hz] 75 125 175 225 ... 1975 Higher Frequencies Active power P/Pn [%] Frequency [kHz] 2,1 2,3 2,5 2,7 ... 8,9
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VDE-AR-N 4105:2011 (E)
F.4
Requirements for the test report for the NS protection Nr. JJJJ - nnnn (consecutive number)
Extract from test report for NS protection "Determination of electrical properties"
NS protection as central NS protection
Type of NS protection: ____________________________________
Software version:
__________________________________
Manufacturer:
__________________________________ __________________________________ __________________________________ __________________________________
Other manufacturer's data
Measuring period: from JJJJ-MM-TT to JJJJ-MM-TT
Protection function
Setting value
Tripping value
Tripping time NS protectiona
Voltage drop protection U <
0,8 * Un
* Un
ms
Rise-in-voltage protection U >
1,1 * Un
* Un
ms
Rise-in-voltage protection U >>
1,15 * Un
* Un
ms
Frequency decrease protection f <
47,5 Hz
Hz
ms
Frequency increase protection f >
51,5 Hz
Hz
ms
a
The tripping time comprises the period before limit violation U/f until tripping signal to interface switch.
During planning of power generation system the proper time of interface switch shall be added to the highest value of time determined above. The break time (sum of tripping time NS protection plus proper time of interface switch) shall not exceed 200 ms.
NS protection as integrated NS protection
Type of NS protection: ________________________________ Software version:
__________________________________
Manufacturer:
__________________________________ __________________________________ __________________________________ __________________________________
Other manufacturer's data Assigned to PGU type
________________
Integrated interface switch Type of Switching equipment 1
________________
Type of Switching equipment 2
________________
Measuring period: from JJJJ-MM-TT to JJJJ-MM-TT
Protection function
Setting value
Tripping value
Break time
Voltage drop protection U <
0,8 * Un
* Un
ms
Rise-in-voltage protection U >
1,1 * Un
* Un
ms
Rise-in-voltage protection U >>
1,15 * Un
* Un
ms
Frequency decrease protection f <
47,5 Hz
Hz
ms
Frequency decrease protection f >
51,5 Hz
Hz
ms
proper time of interface switch
ms
The break time (sum of tripping time NS protection plus proper time of interface switch) shall not exceed 200 ms. The verification of the full functional chain "NS protection – Interface switch" has yield to intended disconnection.
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VDE-AR-N 4105:2011 (E)
Annex G (informative) Forms (optional) G.1
Application
Application for power generation systems connected to the low-voltage network (to be completed by the connection owner)
System address
Connection owner (Owner)
System operator
System erector (Electric company) Type of system
First name, surname
________________________________________
Street, number
________________________________________
ZIP code, city
________________________________________
Telephone, e-mail
________________________________________
First name, surname
________________________________________
Street, number
________________________________________
ZIP code, city
________________________________________
Telephone, e-mail
________________________________________
First name, surname
________________________________________
Street, number
________________________________________
ZIP code, city
________________________________________
Telephone, e-mail
________________________________________
Company, city
________________________________________
Registry number
________________________________________
New erection
Extension
Dismantling
Application form “Application for network connection” enclosed Layout plan enclosed showing the designation and limits of the property as well as the installation site of the power generation system Data sheet of the power generation system enclosed (see form F.2) Certificate of conformity of the power generation unit enclosed (see form G.2) Certificate of conformity of the NS protection enclosed (see form G.3) Overview wiring diagram (single-polar representation) enclosed, starting with the network connection (incl. arrangement of the measuring and protective devices) Planned date for initial start-up
___________
________________________________________
_________________________________________
Place, date
Signature of the connection owner
75
VDE-AR-N 4105:2011 (E)
G.2
Certificate of conformity for power generation units No:YYYY — nnnn (consecutive no.)
Certificate of conformity Power generation unit
Signed copy No. 1
Manufacturer Type power generation unit Assessment values
Network connection rule
Max. active power PEmax
___________ kW
Max. apparent power SEmax
___________ kVA
Rated voltage
___________ V
VDE-AR-N 4105 “Power generation systems connected to the low-voltage network”
Technical minimum requirements for connection and parallel operation of power generation systems connected to the low-voltage network The above mentioned power generation unit meets the requirements of VDE-AR-N 4105. ____________________________________________________________________________________ The certificate of conformity includes the following details: – technical data of the power generation unit, auxiliary equipment used and software version used; –
schematic set-up of the power generation unit;
–
summarized details on the properties of the power generation unit of (mode of action).
____________________________________________________________________________________ Place, date (DD.MM.YYYY)
Manufacturer
____________________________________________________________________________________ This certificate of conformity shall not be used in parts. System manufacturer, company logo, address, e-mail address
76
VDE-AR-N 4105:2011 (E)
G.3
Certificate of conformity of the network and system protection No:YYYY — nnnn (consecutive no.)
Certificate of conformity NS protection
Signed copy No. 1
Manufacturer Type of NS protection Central NS protection Integrated NS protection Network connection rule
Assigned to power generation unit of type VDE-AR-N 4105 “Power generation systems at the low-voltage network”
Technical minimum requirements for the connection and parallel operation of power generation systems connected to the lowvoltage network The network and system protection mentioned above meets the requirements of VDE-AR-N 4105. ___________________________________________________________________________________ The certificate of conformity includes the following details: – the setting values and disconnection times of the protective functions described in 5.5; –
for integrated NS protection the operational functional chain “NS protection — interface switch” as well as the technical data of the breaking devices of the interface switch;
–
the software version used for the NS protection;
–
the check of the self-monitoring in accordance with Annex A “To 5.1, General requirements, single-fault tolerance.”
Place, date (DD.MM.YYYY)
Manufacturer
___________________________________________________________________________________ This certificate of conformity shall not be used in parts. Protective devices manufacturer: Company logo, address, e-mail
77
VDE-AR-N 4105:2011 (E)
Bibliography [1] Eigenerzeugungsanlagen am Niederspannungsnetz (Richtlinie für Anschluss und Parallelbetrieb von Eigenerzeugungsanlagen am Niederspannungsnetz), 4th edition 2011 with VDN supplements (as of September 2005), VDEW/VDN [2] Erzeugungsanlagen am Mittelspannungsnetz (Richtlinie für Anschluss und Parallelbetrieb von Erzeugungsanlagen am Mittelspannungsnetz), Edition of June 2008 with BDEW supplements (as of 15th February 2011), VDN/BDEW [3] TAB 2007, Technische Anschlussbedingungen für den Anschluss an das Niederspannungsnetz, July 2007, Verband der Netzbetreiber VDN e. V. beim VDEW [4] Technische Regeln zur Beurteilung von Netzrückwirkungen, 2nd edition 2007, Verband der Netzbetreiber VDN e. V. beim VDEW [5] Tonfrequenz-Rundsteuerung — Empfehlung zur Vermeidung unzulässiger Rückwirkungen, 3rd edition 1997, VDEW [6] Gesetz zur Neuregelung des Rechts der Erneuerbaren Energien im Strombereich und zur Änderung damit zusammenhängender Vorschriften (Erneuerbare-Energien-Gesetz, EEG 2009). ErneuerbareEnergien-Gesetz of 25th October 2008 (BGBl. I p. 2074), last amended by the Act of 11th August 2010 (BGBl. I p. 1170) [7] Gesetz für die Erhaltung, die Modernisierung und den Ausbau der Kraft-Wärme-Kopplung (Kraft-WärmeKopplungsgesetz, KWK-G). Kraft-Wärme-Kopplungsgesetz of 19th March 2002 (BGBl. I p. 1092), last amended by Article 5 of the Act of 21st August 2009 (BGBl. I p. 2870) [8] MeteringCode, Edition of May 2008, BDEW [9] Ergänzung zur TAB 2007 (Implementation of EEG 2009, § 33, Art. 2 and KWK-G 2009, § 4, Art. 3a to 1st January 2009: Auswirkungen auf Zählerplatz und Messung), October 2009, BDEW
– End of English translation –
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