NZS/ AS 5033

AS/NZS 5033:2005 5033:2005 (Incorporating Amendment No. 1)

A S / N Z S 5 0 3 3 : 2 0 0 5

Australian/New Zealand Standard ™

Installation of photovoltaic (PV) arrays

. e m i t e n o y n a t a m r o f d e t n i r . p t n n i e d m l e u h c o e d b s y i a h t m d o a t o d l n e w b i o r d c s y b l i r u s a r s o t p n m e e m t u o c t o d d e e s h n t e f c i l o % e r 0 a 1 ) n 3 a 8 h 4 t 7 e 4 r 3 ( o m p t u o o r n G t u g b n t i n s e n e m c u i L c o s r d e i s k r t h o t W i l n a r c p i r y t c a e m l E ) f 3 o 8 4 s 7 e 4 e 3 y ( o p l p u o m r E G * g n i s n e c i L s r e k r o W l a c i r t c e l E

AS/NZS 5033:2005

* d n a l a e Z w e N s d r a d n t a S t h g i r y p o C This Joint Australian/New Zealand Standard was prepared by Joint Technical Committee EL-042, Renewable Energy Power Supply Systems and Equipment. It was approved on behalf of the Council of Standards Australia on 8 April 2005 and on behalf of the Council of Standards New Zealand on 15 April 2005. This Standard was published on 19 Ma y 2005.

The following are represented on Committee EL-042:

Alternative Technology Association Australian Electrical and Electronic Manufacturers Association Business Council for Sustainable Energy Electrocomm and Energy Utilities Qualifications Standards Energy Network Association Institution of Professional Engineers, New Zealand Ministry of Economic Development, New Zealand Nation Nat ional al Elec trical tri cal and Comm uni cat ions ion s A ssoci ss ociati ation on New Zea land lan d El ectric ect rical al Ins tit ute Research Institute for Sustainable Energy Sustainable Energy Authority, Victoria University of New South Wales

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This Standard was issued in draft form for comment as DR 03389.

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* d n a l a e Z w e N s d r a d n t a S t h g i r y p o C

NOTES




AS/NZS 5033:2005 5033:2005 (Incorporating Amendment No. 1)

* d n a l a e Z w e Installation of photovoltaic (PV) arrays N s d r a d n t a S t h g i r y p o C Australian/New Zealand Standard ™

First published as AS/NZS 5033:2005. Reissued incorporating Amendment Amendment No. 1 (January 2009).

COPYRIGHT

© Standards Australia/Standards New Zealand All rig hts are res erv ed. No par t of thi s wor k may be rep rod uced or cop ied in any for m or by any means, electronic or mechanical, including photocopying, without the written permission of the publisher. Jointly published by Standards Australia, GPO Box 476, Sydney, NSW 2001 and Standards New Zealand, Private Bag 2439, Wellington 6020

ISBN 0 7337 6699 4

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* d n a l a e Z w e N s d r a d n t a S t h g i r y p o C PREFACE

This Standard was produced by Joint Standards Australia/Standards New Zealand Committee EL-042, Renewable Energy Power Supply Systems and Equipment, with the assistance of the Australian Greenhouse Office (AGO) and the University of NSW.

This Standard incorporates Amendment No. 1 (January 2009). The changes required by the Amendm Ame ndment ent are indicate indi cated d in the text by a margina mar ginall bar and amendm ame ndment ent number num ber against aga inst the clause, note, table, figure or part thereof affected. The objective of this Standard is to prov ide guidance for installers of photovoltaic arrays.

The term ‘informative’ has been used in this Standard to define the application of the appendix to which it applies. An ‘informative’ appendix is only for information and guidance.

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* d n a l a e Z w e N s d r a d n t a S t h g i r y p o C CONTENTS

Page

SECTION 1 SCOPE AND GENERAL 1.1 SCOPE .................................................................. .................................................................................................... ...................................................... .................... 5 1.2 OBJECTIVE....................................................................................... OBJECTIVE................................................................................................................ ......................... 5 1.3 NORMATIVE REFERENCES.................................................... REFERENCES.................................................................................... ................................ 5 1.4 DEFINITIONS ..................................................................... ......................................................................................................... ....................................... ... 7

SECTION 2 PROTECTION REQUIREMENTS 2.1 GENERAL ...................................................................... .......................................................................................................... .......................................... ...... 14 2.2 BYPASS DIODES....................................... DIODES........................................................................... .............................................................. .......................... 14 2.3 BLOCKING DIODES ...................................................................... ............................................................................................... ......................... 14 2.4 FAULT CURRENT PROTECTION PROTECTION ................................................................... .......................................................................... ....... 14 2.5 DISCONNECTING MEANS....................... MEANS........................................................... .............................................................. .......................... 16 2.6 EARTH FAULT PROTECTION PROTECTION ........................................................................ ............................................................................... ....... 17 2.7 ALARMS ........................................................................ ........................................................................................................... .......................................... ....... 19 2.8 LIGHTNING AND OVERVOLTAGE PROTECTION PROTECTION ............................................. ............................................. 19 SECTION 3 WIRING REQUIREMENTS 3.1 COMPLIANCE WITH AS/NZS 3000 ..................................................................... ....................................................................... .. 20 3.2 SYSTEM VOLTAGE.................................... VOLTAGE ........................................................................ ............................................................ ........................ 20 3.3 INSTALLATION WIRING................................ WIRING .................................................................... ....................................................... ................... 20 3.4 CABLE SELECTION.............................. SELECTION.................................................................. .................................................................. .............................. 21 3.5 WIRING IDENTIFICATION ...................................................................... .................................................................................... .............. 22

SECTION 4 COMPONENT REQUIREMENTS 4.1 PV MODULES.......................................................... MODULES.............................................................................................. ................................................ ............ 23 4.2 PV ARRAY AND PV SUB-ARRAY JUNCTION BOXES.................................... BOXES....................................... ... 23 4.3 SWITCHING DEVICES .................................................................. ........................................................................................... ......................... 23 4.4 PLUGS, SOCKET-OUTLETS SOCKET-OUTLETS AND COUPLERS .................................................... .................................................... 24 4.5 FUSES............................................................................................... FUSES....................................................................................................................... ........................ 24 SECTION 5 EARTHING 5.1 GENERAL ...................................................................... .......................................................................................................... .......................................... ...... 25 5.2 PV ARRAY SYSTEM EARTHING .................................................................. .......................................................................... ........ 25 5.3 EARTHING OF EXPOSED CONDUCTIVE PARTS AND EQUIPOTENTIAL BONDING (SYSTEM (SYSTEM BONDING) BONDING) ........................................................................ ........................................................................... ... 29 5.4 EQUIPMENT EARTHING .................................................................... ....................................................................................... ................... 29

SECTION 6 MARKING AND SIGNS 6.1 GENERAL ...................................................................... .......................................................................................................... .......................................... ...... 31 6.2 PV ARRAY AND PV SUB-ARRAY JUNCTION BOXES.................................... BOXES....................................... ... 31 6.3 DISCONNECTION DEVICES............................................. DEVICES................................................................................. ...................................... 31 6.4 FIRE EMERGENCY INFORMATION............................................................. INFORMATION..................................................................... ........ 31 SECTION 7 DOCUMENTATION 7.1 DESIGN INFORMATION .................................................................... ........................................................................................ .................... 32 7.2 COMMISSIONING INFORMATION..................................... INFORMATION....................................................................... .................................. 32

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SECTION 8 COMMISSIONING TESTS 8.1 GENERAL .................................................................. .................................................................................................... .............................................. ............ 33 8.2 OPEN CIRCUIT VOLTAGE...................... VOLTAGE........................................................ ............................................................... ............................. 33 8.3 SOLAR ISOLATION DEVICE TEST............................... TEST................................................................. ........................................ ...... 33 SECTION 9 CASE STUDIES 9.1 GENERAL .................................................................. .................................................................................................... .............................................. ............ 34 9.2 EXAMPLES EXAMPLES ................................................................. ................................................................................................... ............................................. ........... 34

APPENDICES A CHARACTERISTICS CHARACTERISTICS OF PV ARRAYS AND SYSTEMS................................ SYSTEMS....................................... ....... 35 B MECHANICAL SAFETY RECOMMENDATIONS................................................. RECOMMENDATIONS................................................. 38 C FAULT CURRENT ANALYSIS.................................................. ANALYSIS............................................................................... ............................. 39 D EARTHING ISSUES............................................. ISSUES............................................................................... .................................................... .................. 43 E SUGGESTED METHODS OF DETECTION AND AUTOMATIC DISCONNECTION FOR FOR EARTH FAULT FAULT PROTECTION PROTECTION ...................................... ...................................... 49 F LIGHTNING/OVERVOLTAGE PROTECTION PROTECTION ...................................................... ...................................................... 50 G EXAMPLES OF SIGNS............................................................... SIGNS............................................................................................ ............................. 53 H MAINTENANCE REQUIREMENTS ................................................................. ....................................................................... ...... 55 I ADDITIONAL COMMISSIONING TESTS ............................................................. ............................................................. 58 J CASE STUDIES DIAGRAMS ............................................................... .................................................................................. ................... 61

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STANDARDS AUSTRALIA/STANDARDS NEW ZEALAND

* d n a l a e Z w e N s d r a d n t a S t h g i r y p o C Australian/New Zealand Standard

Installation of photovoltaic (PV) arrays

S E C T I O N

1

S C O P E

A N D

G E N E R A L

1.1 SCOPE

This Standard sets out the general installation requirements for photovoltaic (PV) arrays with d.c. open circuit voltages up to 600 V between positive and negative conductors or up to ±600 V with respect to earth and a maximum power of 30 kW. A1

This Standard does not apply to photovoltaic systems or arrays operating at less than 25 V d.c. and with a power of less than 25 W. NOTE S: 1

This includes the following PV array configurations (refer to Figures 1.1 and 1.2)—

(a)

Single string of modules.

(b)

Multi-string PV array.

(c)

PV array divided into several sub-arrays.

2

Direct current systems, and photovoltaic systems in particular, pose some hazards in addition to those derived from conventional a.c. power systems, including the ability to produce and sustain electrical arcs with currents that are not much greater than normal operating currents. This Standard addresses the safety requirements arising from the particular characteristics of photovoltaic systems. A discussion of those characteristics is presented in Appendix A.

3

Although this Standard does not cover PV array systems with a power greater than 30 kW, similar principles can be used for such systems.

1.2

OBJECTIVE

The objective of this Standard is to provide electrical safety and fire protection requirements for— (a) (b) (c)

uninformed persons, including owner(s)/occupier(s) and users of the premises where photovoltaic arrays are installed; informed workers (e.g. electricians) working on these systems; and

emergency workers.

NOTE : Me cha nica l s afety afe ty reco mm mmend endati ations ons are given giv en in Appendi Appe ndix x B.

1.3 NORMATIVE REFERENCES

AS 1319

Safety signs for the occupational environment

60529

Degrees of protection provided by enclosures (IP Code)

4509 4509.1 4509.2

Stand-alone power systems Part 1: Safety requirements Part 2: System design guidelines

AS/NZS 1170 1170.2

Structural design actions Part 2: Wind actions COPYRIGHT

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1768

Lightning protection

3000

Electrical installations (known as the Australian/New Zealand Wiring Rules)

3008 3008.1.1

Electrical installations—Selection installations—Selection of cables Part 1.1: Cables for alternating voltages up to and including 0.6/1 kV—Typical Australian installation conditions Part 1.2: Cables for alternating voltages up to and including 0.6/1 kV—Typical New Zealand Zeal and installa ins tallation tion conditio cond itions ns

3008.1.2 3100

Approval and test specification—General specification—General requirements for electrical equipment

3112

Approval and test specification—Plugs specification—Plugs and socket outlets

3123

Approval and test specification—Plugs, specification—Plugs, socket-outlets and couplers for general industrial application

3133

Approval and test specification—Air break switches

3190

Approval and test specification—Residual specification—Residual current devices (current-operated earth-leakage devices)

61008

Residual current-operated circuit-breakers without protection for household and similar uses ( RCCBs) Part 1: General rules

61008.1 61009

61009.1

IEC 60309 60309-2 61215

A1

A1

integral

overcurrent

Residual current operated circuit-breakers with integral overcurrent protection for household and similar uses (RCBOs) Part 1: Residual current operated circuit-breakers with integral overcurrent protection for household and similar uses ( RCBOs)—General rules

Plugs, socket-outlets and couplers for industrial purposes Part 2: Dimensional interchangeability requirements for pin and contact-tube accessories Crystalline silicon terrestrial photovoltaic (PV) modules—Design qualification and type approval

61643 61643-12

Low voltage surge protective devices Part 12: Surge protective devices connected to low voltage power distribution systems—Selection and application principles

61646

Thin-film terrestrial photovoltaic (PV) modules—Design qualification and type approval

61730 61730-1 61730-2

Photovoltaic module safety qualification Part 1: Requirements for construction Part 2: Requirements for testing

61829

Crystalline silicon photovoltaic (PV) array—On-site measurement of I-V characteristics

EN

61730 61730-1 61730-2

Photovoltaic (PV) module safety qualification Part 1: Requirements for construction Part 2: Requirements for testing

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1.4 DEFINITIONS


1.4.1 Accessible, readily

Capable of being reached quickly and without climbing over or removing obstructions, standing on a chair, or using a movable ladder, and in any case not more than 2.0 m above the ground, floor or platform. 1.4.2 Active (or active conductor)

Any conductor which is maintained at a difference of potential from the neutral or earthed conductor. In a system which does not include a neutral or earthed conductor, all conductors shall be considered to be active conductors. 1.4.3 Available, readily

Capable of being reached for inspection, maintenance or repairs without necessitating the dismantling of structural parts, cupboards, benches or the lik e. 1.4.4 Bypass diode

A diode that is connected in parallel with a PV module, or a group of PV cells within a PV module, and prevents the PV module or group of cells from being reverse biased (see Figures 1.1 and 1.2). 1.4.5 Cable

A single cable core, or two or more cable cores laid up together, either with or without fillings, reinforcements, or protective coverings. 1.4.6 Cable, armoured

A cable provided with a wrapping of m etal, usually tapes or wires, primarily for the purpose of mechanical protection. 1.4.7 Cable core

The conductor with its insulation but not including any mechanical protective covering. 1.4.8 Class II equipment

Equipment in which protection against electric shock does not rely on basic insulation only, but in which additional safety precautions such as double insulation or reinforced insulation are provided, there being no provision for protective earthing or reliance upon installation conditions. Such equipment may be one of the following types: (a)

(b)

(c)

Equipment having durable and substantially continuous enclosures of insulating material which envelops all metal parts, with the exception of small parts, such as nameplates, screws and rivets, which are isolated from live parts by insulation at least equivalent to reinforced insulation; such equipment is called insulation-encased Class II equipment.

Equipment having a substantially continuous metal enclosure, in which double insulation is used throughout, except for those parts where reinforced insulation is used, because the application of double insulation is manifestly impracticable; such equipment is called metal-encased Class II equipment. Equipment that is a combination of the types described in Items (a) and (b).

NOTE S: 1

The enclosure of insulation-encased Class II equipment may form part of the whole of the supplementary insulation or of the reinforced insulation.

2

If the equipment with double insulation or reinforced insulation throughout has an earthing terminal or earthing contact, it is considered to be of Class I construction.

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3

Class II equipment may be provided with means for maintaining the continuity of protective circuits, insulated from accessible conductive parts by double insulation or reinforced insulation.

4

Class II equipment may have parts operating at SELV.


1.4.9 Insulation monitor

A device that periodically measures the resistance to earth of each pole of the PV array output circuit, and produces an alarm signal when the resistance values fall under a specified limit. 1.4.10 Installation earth

When a PV array is installed on a building, the installation earth is the earthing bar or earthing rod of the building. For freestanding PV arrays, the installation earth is the earthing bar or earthing rod of the PV system. 1.4.11

I SC S C ARRAY

The short circuit current of the PV array at standard test conditions, and is equal to: I SC ARRAY = I SC MOD

where

S A is

1.4.12

I SC

×

S A

the total numb er of parallel-connected PV strings in the PV array

MOD

The short circuit current of a PV module or PV string at standard test conditions, as specified by the manufacturer on the product specification plate.

NOTE : As PV string str ing s a re a group grou p of PV modu les con nected nec ted in ser ies , t he shor t circ c irc uit current cur rent of a string is equal to I SC MOD .

1.4.13

I MOD MOD REVERSE

The current a module can withstand in the reverse direction to normal without damage to the module. This rating shall be obtained from the manufacturer at expected operating conditions. NOTE S: 1

This current rating does not relate to bypass diode rating. The module reverse current is the current flowing through the PV cells in the reverse direction to normal current.

2

A typical figure for crystalline silicon modules is between 2 and 2.6 times the normal short circuit current rating I SC MOD.

1.4.14

I SC

S-ARRAY

The short circuit current of a PV sub-array at standard test conditions, and is equal to: I SC S-ARRAY

where

S SA SA is

= I SC MOD ×

S SA

the number of parallel-connected PV strings in the PV sub-array

1.4.15 Junction box

An enclosure where cables are joined, terminated or connected to electrical equipment and/or protective devices. 1.4.16 Live part

A conductor or conductive part intended to be energized in normal use. 1.4.17

P ARRAY

The nominal power of the PV array calculated as the sum of the nameplate power ratings of all the PV modules that constitute the array. COPYRIGHT

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1.4.18 PELV (protected extra-low voltage)


An extra-low voltage system which is not electrically separated from earth, but which otherwise satisfies all the requirements for SELV. 1.4.19 Power conditioning unit (PCU)

A unit that converts the electrical power delivered by the PV array into the appropriate frequency and/or voltage to be delivered to the load, or stored in a battery or injected into the electricity grid (see Figures 1.1 and 1.2). NOTE : An A n i nve nverte rterr i s an a n exam e xam ple of a po wer cond itioni iti oning ng uni t.

1.4.20 Power conditioning unit (PCU), isolated

A power conditioning unit where there is electrical isolation between the input and output circuits. NOTE : One O ne mea ns of achi evi ng this thi s iso lati on is by usi ng an isolat iso lation ion transf tra nsform ormer er

1.4.21 Power conditioning unit (PCU), non-isolated

A power conditioning unit (PCU) where there is no electrical isolation between the input and output circuits. 1.4.22 PV array

An electrically integrated assembly of PV modules, and other necessary components, to form a d.c. power supply unit. A PV array may consist of a single PV module, a single PV string, or several parallel-connected strings, or several parallel-connected PV sub-arrays and their associated electrical components (see Figures 1.1 and 1.2). The boundary of a PV array is the connection to the PV array cable at the PV array junction box (or equivalent location, if there is no junction box, e.g. output side of the isolator). Two or more PV arrays, which are not interconnected in parallel on the generation side of the power conditioning unit (PCU), shall be c onsidered as independent PV arrays. 1.4.23 PV array cable

The output cable of a PV array that connects the PV array junction box (or equivalent location) to the power conditioning unit (PCU), battery or load (see Figures 1.1 and 1.2). 1.4.24 PV array, earthed

A PV array where one of the poles of the d.c. output circuit is electrically connected to earth.

NOTE : PV arra ys conn ect ed to eart hed batt ery syst sy stems ems via a ser ies regu lat or on the earthe ear thed d conductor (i.e. the regulator switches the earthed conductor) are deemed to be earthed PV arrays for the purposes of this Standard.

1.4.25 PV array, floating

A PV array not referenced to earth in any way. Thus neither the positive nor the negative connection are connected to earth and there is no centre tapped arrangement (e.g. resistive or capacitive bridge) connected to earth. 1.4.26 PV array, isolated

A PV array where there is electrical separation between the PV array output circuit and the a.c. system. NOTE : One O ne mea ns of achi evi ng electr ele ctrica icall i sola tion is by usi ng an isolat iso lation ion tran sforme sfo rme r.

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1.4.27 PV array junction box


An enclosure where all the PV strings of a PV array (in the not subdivided PV array case, see Figure 1.1) or all the PV sub-arrays of a PV array (in the subdivided PV array case, see Figure 1.2) are electrically connected in parallel and where protection devices may be located, if necessary. 1.4.28 PV array voltage

The PV array voltage shall be considered to be equal to V OC O C ARRAY . NOTE : The open circ uit volt age is depe nden t on o n t he c ell tempera tem pera ture. tur e.

1.4.29 PV cell

The basic unit of photovoltaic conversion; a semiconductor device that can convert light directly into electrical energy. 1.4.30 PV module

An assembly of several PV cells electrically connected to form a larger photovoltaic conversion device, and which are encapsulated together to protect them from the environment. A PV module is the smallest ready to use photovoltaic conversion device (see Figure 1.1). 1.4.31 PV module junction box

An enclosure affixed to a PV module, where the electrical connections to the PV module are made. 1.4.32 PV string

A circuit formed by one or more series connected PV modules. The series connection of PV modules to form a PV string is intended to provide the required circuit voltage (see Figure 1.1). 1.4.33 PV string cable

The cable connecting the modules in a PV string, and/or connecting the string to the PV sub-array junction box or to the PV array junction box (or equivalent location, if there is no junction junc tion box) box ) (see ( see Figure Figu re 1.1). 1.1 ). 1.4.34 PV sub-array

A group of PV strings connected in parallel, that comprise a partial section of the PV array, where the output current of that group of strings is carried by a dedicated output cable before being connected in parallel with other sub-arrays. NOTE : No t all a ll PV arra ys are divi ded int o subs ub-arra arra ys.

1.4.35 PV sub-array cable

The output cable of a PV s ub-array that carries only the output current of its associated subarray in normal operation, and that connects the PV sub-array with the other PV sub-arrays that constitute the PV array.

NOTE : PV sub- arra y cables cab les are onl y rel eva nt for PV arra ys tha t are divi ded into int o sub-arr sub -arr ays (se e Figures 1.1 and 1.2 for clarification).

1.4.36 PV sub-array junction box

An enclosure where all the PV strings of a PV sub-array are electrically connected in parallel and where protection devices may be located if necessary (see Figure 1.2). NOTE : PV sub-ar sub -array ray jun cti on boxe s are only onl y rel evant eva nt for PV arrays arr ays tha t are div ided into sub arrays (see Figures 1.1 and 1.2 for clarification).

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1.4.37 Ripple-free d.c.


For sinusoidal ripple voltage, a ripple content not exceeding 10% r.m.s.

NOTE : The refore ref ore the maxim max imum um peak pea k val ue does not exceed exc eed 140 V for a nomina nom ina l 120 V ripp lefree d.c. system and 70 V for a nominal 60 V ripple-free d.c. system.

1.4.38 SELV (separated extra-low voltage)

An extra-low voltage system which is electrically separated from earth, and from other systems, in such a way that a single fault cannot give rise to the risk of electric shock. 1.4.39 Shall

Indicates that a statement is mandatory. 1.4.40 Should

Indicates that a statement is a recommendation. 1.4.41 STC (standard test conditions)

A standard set of reference conditions used for the testing and rating of photovoltaic cells and modules. The standard test conditions are: (a) (b) (c)

PV cell temperature of 25°C.

Irradiance in the plane of the PV cell or module of 1 000 W/m 2.

Light spectrum corresponding to an atmospheric air mass of 1.5.

1.4.42

V OC ARRAY

The open circuit voltage at standard test conditions of a PV array, and is equal t o: V OC O C ARRAY = V OC OC MOD × M

Where M Where M is is the number of series-connected PV modules in any PV string of the PV array.

NOTE : This Th is Sta ndard ndar d ass ume s tha t all string str ing s wit hin a PV array arra y are connect con nect ed in para llel; lle l; hen hence ce the open circuit voltage of PV sub-arrays and PV strings is equal to V OC O C ARRAY .

1.4.43

V OC

MOD

The open circuit voltage of a PV module at STC, as specified by the manufacturer in the product specification. 1.4.44 Voltage

Differences of potential normally existing between conductors and between conductors and earth as follows: (a) Extra-l Extr a-low ow volta v oltage ge (ELV)

Not exceeding 50 V a.c. or 120 V ripple-free d.c.

(b) Low voltage volt age (LV)

Exceeding extra-low voltage, but not exceeding 1 000 V a.c. or 1 500 V d.c.

NOTE : When Wh en cal culati cul ati ng the volt age of a PV P V ar ray, ray , V OC O C ARRAY is to be used.

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NOTE S: 1

2

If there are no string fault current protection devices present, the parallel connection of PV strings may be done within the PV module junction boxes, as long as the current rating of the terminal strips is— (a)

greater than the nearest fault current protection device; or

(b)

greater than I SC ARRAY .

The PV array overcurrent protection devices and the elements shown in the PV array junction box are not required in all cases. (Refer to Appendix J for specific case studies.)

FIGURE 1.1 PV ARRAY DIAGRAM: CASE WHERE ARRAY NOT DIVIDED INTO SUB-ARRAYS COPYRIGHT

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NOTE : The PV arra y o verc urre nt prot ection ect ion device dev icess and the elem ent s wit hin the PV arra y and PV sub-array junction boxes are not required in all cases. (Refer to Appendix J for specific c ase studies.)

FIGURE 1.2 PV ARRAY DIAGRAM: CASE WHERE ARRAY IS DIVIDED INTO SUB-ARRAYS

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S E C T I O N

2

P R O T E C T I O N

R E Q U I R E M E N T S

2.1 GENERAL

The installation of PV arrays shall comply with the requirements of AS/NZS 3000 except as varied var ied herein here in and with the addition addi tional al require requ iremen ments ts of this Standard Stan dard . The provis pro vision ionss of this thi s section are aimed at ensuring that these requirements are met, taking into account a range of system configurations and earthing arrangements. 2.2 BYPASS DIODES

Bypass diodes may be used to prevent PV modules from being reverse biased and consequent hot spots occurring. If bypass diodes are added by the installer, they shall comply with all the following requirements: (a) (b) (c) (d)

Have a voltage rating of at least 2

×

V OC OC MOD of the protected module.

Have a current rating of at least 1.25

× I SC SC

MOD

.

Be installed so no live parts are exposed.

Be protected from degradation due to environmental factors.

2.3 BLOCKING DIODES

Blocking diodes may be used but they are not a substitute for fault current protection. One of their purposes is to prevent reverse currents from battery systems leaking into a PV array at night, when this protection is not an integral part of the battery charge controller. If used, blocking diodes shall comply with all the following r equirements: (a) (b)

(c) (d)

Have a voltage rating of at least 2

×

V OC O C ARRAY .

Have a current rating of at least 1.3 times the short circuit current at STC of the circuit that they are intended to protect. That is—

(i)

1.25 × I SC S C MOD for PV strings;

(ii)

1.25 × I SC S C S-ARRAY for PV sub-arrays; or

(iii)

1.25 × I SC S C ARRAY for PV arrays.

Be installed so no live parts are exposed.

Be protected from degradation due to environmental factors.

2.4 FAULT CURRENT PROTECTION

2.4.1 Number of of parallel strings without overcurrent protection

The maximum number of strings connected in parallel without overcurrent protection shall be nP where nP is related to the PV modules reverse current rating and is given by Table 2.1 unless the conditions of Clause 2.4.3 apply. If I MOD M OD REVERSE is not obtainable from the manufacturer of the PV modules, nP shall be taken as 1. 2.4.2 Discrimination

Fault current protection of the PV array installation shall be graded in such a way that lower level protection trips first in the event of fault currents flowing from higher current sections to lower current sections of the PV array installation. NOTE : When Wh en circui cir cuitt brea kers wit h fault fau lt curr ent protect prot ection ion ele ments men ts are used, use d, they the y als o provide prov ide the disconnecting means required in Clause 2.5. COPYRIGHT

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AS/ NZS 5033 :200 5

TABLE 2.1


NUMBER OF PARALLEL STRINGS WITHOUT OVERCURRENT PROTECTION nP

nP

Module reverse current rating - I SC MOD REVERSE

1 (i.e. no paralleling)

I MOD REVERSE < I SC MOD

2

1

× I SC MOD ≤ I MOD REVERSE

<2

× I SC MOD

3

2


<3

× I SC MOD

4

3


<4

× I SC MOD

5

4


<5

× I SC MOD

2.4.3 PV strings

Where there are more than nP parallel connected strings, fault current protection shall be installed unless the array is ELV and— (a)

(b)

the PV modules are mounted in such a way and location that an arc or molten metal coming out of the back of any of the PV modules shall not result in property damage or risk to the lives of people or animals; or

the PV modules are of a type which prevents any molten metal coming out of the back of the module.

NOTE : In lar ger sys tem s fault fau lt current curr ent protect prot ect ion should sho uld be consid con sidered ered (se e Appe ndix ndi x A for explanation).

The rated trip current ( I ( I TRIP T RIP) of fault current protection devices for PV strings shall be as specified by the PV module manufacturer. If the manufacturer does not give any recommendation, I recommendation, I TRIP T RIP shall be determined by the following formula: 1.25 × I SC SC MOD ≤ I TRIP T RIP ≤ 2 × I SC S C MOD

NOTE : Appen A ppendix dix C give g ivess e xample xam pless o f a num number ber of eart h f ault aul t condi c ondi tions. tio ns.

2.4.4 PV sub-arrays (subdivided PV PV arrays only)

ELV PV arrays, where the PV modules are mounted in such a way and location that an arc or molten metal coming out of the back of the PV module shall not cause a fire, do not require PV sub-array fault current pr otection. For LV, PV sub-arrays, fault current protection shall be provided.

The rated trip current ( I TRIP T RIP ) of fault current protection devices for PV sub-arrays shall be determined by the following formula: 1.25 × I SC S C S-ARRAY ≤ I TRIP T RIP ≤ 2 × I SC S C S-ARRAY .

2.4.5 PV array cables

PV array cables of systems connected to batteries shall be protected with fault current protection devices.

The trip current ( I TRIP T RIP ) of PV array fault current protection devices shall be determined by the following formula: 1.25 × I SC S C ARRAY ≤ I TRIP T RIP ≤ 2 × I SC S C ARRAY

NOTE : Fa ult current curr ent prote ction cti on devi ces are common com monly ly ins tal led betwee bet wee n the batter bat ter y and the charge controller. If these devices are appropriately rated, they provide protection to both the charge controller and the PV array cable. In such cases, no further PV array cable fault current protection is required between the PV array and the charge controller.

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2.4.6 Location of fault current protection devices


Table 2.2 sum marizes the location of fault current protection devices, if required by Clauses 2.4.1 to 2.4.5. TABLE 2.2

LOCATION OF FAULT CURRENT PROTECTION DEVICES Location of protection devices

System configuration

PV string cables

Floating array double insulated with respect to earth

PV sub-array cable

In one active conductor

Floating array single insulated Earthed PV array

PV array cable

In all active conductors

In all active conductors

Array connected to load via a nonisolated power conditioning unit

NO TE: Activ Ac tiv e c ondu ctors cto rs are thos e not n ot direct dir ect ly connect conn ect ed to ear th.

Fault current protection devices, where required by Clauses 2.4.2 through 2 .4.5 for PV strings, PV sub-arrays and PV arrays, shall be at the load (downsteam) end of those cables.

NOTE : Becau Be cause se PV string str ing s/arra s/a rrays ys are inh eren tly cur rent lim ite d, the source sou rce of fau lt curr ent is likely to be from other parallel connected strings/sub-arrays or from batteries. Hence, the protection needs to be near the parallel connection point (i.e. the load end)

2.5 DISCONNECTING MEANS 2.5.1 General

Disconnecting means shall be provided in PV arrays according to Clauses 2.5.2 to 2.5.4, to isolate the PV array from the power conditioning unit (PCU) and vice versa, and to allow for maintenance and inspection tasks to be carried out safely. In ELV stand-alone systems the disconnecting means may be located between the charge regulator and the battery as required in AS 4509.1.

NOTE : This Th is Cla use does doe s not apply appl y to module mod ule inv erte rs whe re the inv erte r is an int egra l part of the PV module.

2.5.2 Selection and installation

A circuit-breaker installed for fault current protection may also provide isolation, if it is rated as an isolation device. Isolation switches complying with AS/NZS 3133 may be used to provide isolation.

Plugs and socket-outlets complying with the requirements of Clause 4.4 may be used to provide disconnection and isolation.

Fuse systems, which are used for fault current protection, are acceptable non-load breaking disconnecting means, if they have removable fusing elements, preferably with a disconnection mechanism (fuse-combination unit). For a reference to the location of disconnection devices see Figures 1.1 and 1.2. 2.5.3

Disconnection device requirements

Table 2.3 specifies disconnection device requirements for PV array installations. Table 2.4 specifies the location of these devices, when required.

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TABLE 2.3


DISCONNECTION DEVICE REQUIREMENTS IN PV ARRAY INSTALLATIONS PV array vol tage tag e

Circuit or sub-circuit

Type of disconnection device

Array cable OR between regulator and battery as required by AS 4509.2

ELV

String cable

LV

Readily available load-breaking disconnection device

Readily available disconnection device

Sub-array cable

Readily available load-breaking disconnection device

Array cable

Readily available load-breaking disconnection device, lockable in the off position

TABLE 2.4

LOCATION OF DISCONNECTION DEVICES ACCORDING TO SYSTEM CONFIGURATION Location of disconnecting devices

System configuration

PV string cables

PV sub-array cables

Unearthed PV array

In all active 1) conductors

PV array cable In all active 1) conductors

In all current carrying conductors 2)

Earthed PV array

1)

Active conductors are those those not directly connected to earth.

2)

The disconnection device is required in this situation to interrupt the earth bonding bonding conductor so that earth fault currents may be interrupted.

2.5.4 Extra-low voltage segmentation

In low voltage PV arrays, means shall be provided to sectionalize each PV string into segments whose open circuit voltage at STC is within the ELV range. 2.6 EARTH FAULT PROTECTION 2.6.1 General

Earth fault detection requirements specified in this Clause are intended for electric shock and fire protection. These requirements are set out in Table 2.5. NOTE S: 1

Earth faults in PV array installations are potentially dangerous because of the risks associated with a floating array being inadvertently earthed, or the development of fault currents and arcs in earthed arrays. The risk level associated with earth faults depends on several factors, such as the voltage and current ratings of the PV array, equipment class and on the PV array location (ground mounted or on a building).

2

See Appendix D for further information on earthing issues.

Examples of possible locations for earth fault protection devices are shown in Figure 2.1

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m r o f d e t n i r . p t n n i e d m l e u h c o e d b s y i a h t m d o a t o d l n e w b i o r d c s y b l i r u s a r s o t p n m e e m t u o c t o d d e e s h n t e f c o i l % e C r 0 a O 1 P )Y n 3 a 8 R h 4 I t G 7 e 4 H r 3 (T o m p t u o o r n G t u g b n t i s n n e e m c u i L c o s r d e i s k r h o t t W i l n a r c p i r y t c a e m l E ) f 3 o 8 4 s 7 e 4 e 3 y ( o p l p u o m r E * G g n i s n e c i L s r

* d n a a l a e Z w e N s d d r a d n a a t S t h g g i r y p o C TABLE 2.5

EARTH FAULT PROTECTION REQUIREMENTS

V OC

Arr ay

Syst em

Floating

d.c. load(s) only (i.e. stand-alone system with no a.c. loads)

Floating

Isolated PCU(s) with d.c. and/or a.c. loads

Non ear thed the d

Earthed

V OC

ARRAY

≤ 50

V

50 V < V OC ARRAY ≤ 120 V

> 120 V

OR

Systems which contain a voltage > ELV where there is not electrical isolation between the array and that voltage (refer to AS/NZS 3000)

Double or reinforced insulation 1) , or automatic disconnection of PV supply to load 2)

No requir req uirem ement ent

Double or reinforced insulation 1) , or alarm indicating fault, or automatic disconnection of PV supply to power conditioning unit 2

Grid-connected system connected via a non-isolated PCU(s) 3) (a) d.c. load(s) only (i.e. stand-alone system with no a.c. loads)

ARRAY

Double or reinforced insulation 1)

No requ ire men t

Double or reinforced insulation 1) , or automatic disconnection of PV supply and disabling of earth fault current path 2), 4)

(b) Isolated PCU(s) (a.c. and/or d.c. loads) 1)

A PV array installation is deemed to comply with double double insulation if it complies with the requirements of Clause 5.4 (a).

2)

Suggested methods for automatic disconnection are given in Appendix E.

3)

This configuration is applicable only to grid-connected systems. In this case , the PV array is referenced to earth via the grid interconnection and therefore will not be floating.

4)

Not required on ground ground mounted ELV PV arrays where there is minimal risk of personal or property damage if a fire occurs in the array (s ee Clause 2.4).

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. e m i t e n o y n a t a m r o f d e t n i r . p t n n i e d m l e u h c o e d b s y i a h t m d o a t o d l n e w b i o r d c s y b l i r u s a r s o t p n m e e m t u o c t o d d e e s h n t e f c i l o % e r 0 a 1 ) n

A S / N Z S 5 0 3 3 : 2 0 0 5

AS/ NZS 5033 :200 5

* d n a l a e Z w e N s d r a

FIGURE 2.1 LOCATION OF EARTH FAULT PROTECTION DEVICES AND THEIR THE IR ASS OCIATE OCI ATED D D ISC ONNECT ONN ECTION ION DEVICE DEV ICE

2.6.2 Earth fault protection settings

Detection devices based on insulation resistance measurement, where required, shall operate when the insulation resistance between any of the active conductors and earth is less than 36/A MΩ, where A is the PV array area in m 2. Detection devices based on earth leakage or residual current measurement, where required, shall operate before the leakage or residual current exceeds 30 m A (see Appendix D) .

1 8

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AS/ NZS 5033 :200 5

* d n a l a e Z w e N s d r a d n t a S t h g i r y p o C FIGURE 2.1 LOCATION OF EARTH FAULT PROTECTION DEVICES AND THEIR THE IR ASS OCIATE OCI ATED D D ISC ONNECT ONN ECTION ION DEVICE DEV ICE

2.6.2 Earth fault protection settings

Detection devices based on insulation resistance measurement, where required, shall operate when the insulation resistance between any of the active conductors and earth is less than 36/A MΩ, where A is the PV array area in m 2. Detection devices based on earth leakage or residual current measurement, where required, shall operate before the leakage or residual current exceeds 30 m A (see Appendix D) . 2.7

ALARMS

2.7.1 Visual alarms

Visual alarms, where used, should be located where the system owner and/or service personnel can easily see them. NOTE : See S ee Sectio Sec tion n 7 regardi reg ardi ng docu mentat men tat ion for alarms ala rms .

2.7.2 Audible alarms

Audible alarms, where used, should be placed where the system owner and/or service personnel can easily hear them. NOTE : See S ee Sectio Sec tion n 7 regardi reg ardi ng docu mentat men tat ion for alarms ala rms .

2.8 LIGHTNING AND OVERVOLTAGE PROTECTION 2.8.1 Lightning protection

Lightning protection measures may be required in some PV installations. The need for lightning protection should be assessed in accordance accordance with AS/NZS 1768. Appendix F gives guidance on the assessment of lightning protection requirements. 2.8.2 Overvoltage protection

Overvoltage protection measures include— (a)

equipotential bonding;

(b)

avoidance of wiring loops;

(c)

installation of surge arrestors; and

(d)

shielding.

NOTE : See S ee Appendi Appe ndix x F for addi tion al inf orma tion. tio n.

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* d n a l a e Z w e N s d r a d n t a S t h g i r y p o C S E C T I O N

3

W I R I N G


3.1 COMPLIANCE WITH AS/NZS 3000

The installation of wiring associated with PV array systems shall be in accordance with AS/NZS 3000 except as varied herein and with the additional requirements of this Standard.

NOTE : Parti Pa rti cular cul ar attent att ent ion needs nee ds to be given giv en to the prot ect ion of wir ing sys tem s agains aga ins t extern ext ernal al influences.

3.2 SYSTEM VOLTAGE

V OC O C ARRAY shall not exceed the maximum allowed operating voltage of the PV modules (as specified by the manufacturer). 3.3 INSTALLA TION WIRING 3.3.1 General

The wiring for PV arrays shall be arranged to minimize the possibility of line-to-line and line-to-earth faults occurring.

All connections shall be verified for tightness and polarity during installation. (This is to reduce the risk of faults and possible arcs occurring during commissioning and operation.) 3.3.2 Wiring loops

The PV array wiring should be laid in such a way that the area of conductive loops is minimized ( e.g. b y laying cables in parallel as shown in Fig ure 3.1) (see also Paragraph F2.2).

FIGURE 3.1

PV STRING WIRING WITH MINIMUM LOOP AREA COPYRIGHT

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AS/ NZS 5033 :200 5

3.3.3 String wiring


If the wiring of PV strings between modules is not in conduit, all the following shall apply: (a) (b) (c)

Insulated and sheathed cables shall be used.

Cables shall be protected from mechanical damage.

Cables shall be clamped (to relieve tension and to prevent conductors coming free from connections).

3.3.4 Wiring installation in junction boxes

The following provisions apply to the installation of wiring systems i n junction boxes: (a)

(b)

Where conductors enter a junction box without conduit, a tension relief system shall be used to avoid cable disconnections inside the junction box (for example by using a gland connector). All cable entries shall maintain the IP rating of the enclosure.

NOTE : Wa ter condens cond ens ation ati on ins ide juncti jun ction on boxe s may be a probl em in som e locati loc ations ons and provision may be needed to drain water build-up.

(c)

For LV PV arrays, where a return conductor is routed through module junction boxes, such return conductor(s) shall be a single-core double-insulated cable, and the cable and its insulation shall maintain double insulation status over its entire length, particularly through junction boxes (i.e. these provisions also apply to the joints, if any).

NOTE : Th is require requ ire ment men t is to provi de double doub le ins ulatio ula tio n betw een the ret urn conduct con duct or and exposed metal terminals in junction boxes.

3.3.5 Location of PV array and PV sub-array junction boxes

PV array and PV sub-array junction boxes, where installed, shall be readily available. 3.4 CABLE SELECTION 3.4.1 Cable size

The minimum cable sizes for PV array wiring, based on current carrying capacity, shall be based upon a current rating calculated from Table 3.1, and the current carrying capacity of cables as specified in AS/NZS 3008.1 series, where the a.c. to d.c. conversion factor is taken as 1.0. NOTE : When Wh en cal culati cul ati ng cable cabl e s ize, ize , cons c ons iderati ider ati on needs nee ds to be b e give g ive n to— t o— (a)

voltage drop (a maximum of 5% is recommended); and

(b)

de-rating of the current carrying capacity of a cable due to temperature.

3.4.2 Insulation

The insulation of cables used within the PV array installation shall— (a)

have a voltage rating of at least 1.2

×

V OC O C ARRAY ;

NOTE : The T he use of sin gle core ins ulated ula ted and she ath ed cable cabl e is reco mme nded for wir ing of PV array installations where V OC ARRAY ≥120 V d.c. to minimi ze the risk of faults wi thin the wiring.

(b)

have a temperature rating according to the application; and NOTE : PV P V module mod uless frequen fre quen tly tl y opera te at temper tem peratu atures res of the orde r of 40 K abov e amb ient ien t temperature. Cable insulation of wiring installed in contact with, or near, PV modules needs to be rated accordingly.

(c)

if exposed to the environment, be UV resistant, or be protected from UV light by appropriate protection (e.g. installed in UV resistant conduit).

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TABLE 3.1

* d n a l a e Z w e N s d r a d n t a S t h g i r y p o C CURRENT RATING OF PV ARRAY CIRCUITS

Minimum current upon which cable cross-sectional area should be chosen 1)

Type of cable

1

PV string cable (PV string fault current protection not provided)

2)

Rated trip current of the nearest downstream fault current protection device + 1.25 × I SC MOD × ( S PO −1) where S PO is

the number of parallel connected strings protected by the nearest fault current protection device.

NO TE: Whe n no fau lt curr ent prot ect ion is use d, S PO is the total number of parallel connected strings in the PV array, and the trip current of the nearest fault current protection device is replaced by zero.

2

3

PV string cable (PV string fault current protection provided)

Rated trip current 2) of the PV string fault current protection device (See Figure 1.1)

PV sub-array cable (PV sub-array fault current protection not provided)

The greater of the following calculations:

(a) Rated trip current 2) of the PV array fault current protection device + 1.25 × sum of short circuit current of all other subarrays

(b) 1.25

×

I SC S-ARRAY (of

relevant array).

Not e: When Whe n PV P V arra a rray y fault fau lt curren cur rentt prot p rotect ection ion is not used, use d, the corresponding parameter is replaced by zero in equation (a).

4

5

6

1)

2)

PV sub-array cable (PV sub-array fault current protection provided)

Rated trip current 2) of the PV sub-array fault current protection device (See Figure 1.2)

PV array cable (PV array fault current protection not provided)

1.25 × I SC ARRAY

PV array cable (PV array fault current protection provided)

Rated trip current of the PV array fault current protection device (See Figures 1.1 and 1.2)

2)

The operating temperature of PV modules and consequently their associated wiring can be significantly higher than the ambient temperature. A minimum temperature rise above maximum expected ambient temperature of +40 K should be considered for cables installed near, or in contact with, PV modules. The AS/NZS 3008.1 series contains appropriate cable temperature derating factors. The rated trip current will be be greater than the nominal rated current current of the PV string/sub-array/array.

3.5 WIRING IDENTIFICATION

Where PV array cabling could be confused with other wiring systems, appropriate identification shall be provided at regular intervals. NOTE : Typic Ty picall all y, iden tif icat ion should sho uld be n ot more tha n 3 m a part .

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S E C T I O N

4

C O M P O N E N T


4.1 PV MODULES 4.1.1 Reliability

Crystalline silicon PV modules shall comply with IEC 61215. Thin film PV modules shall comply with IEC 61646. 4.1.2 Equipment class*

PV modules should be Class II. 4.1.2 Equipment class† A1

PV modules shall comply with the requirements of IEC 61730-1 and IEC 61730-2 or EN 61730-1 and EN 61730-2. PV modules for systems operating at greater than 50 V or greater than 240 W shall comply with Class A of the above Standards.

PV modules for systems operating at less than 50 V and less than 240 W may comply with Class C of the above Standards.

Modules complying with Class B requirements of the above Standards shall not be used in Australia and New Zealand. NOTE : Cl ass B does do es not prov ide suffic suf fic ien t i nsu lation lat ion for saf e usag u sag e.

4.2 PV ARRAY AND PV SUB-ARRAY JUNCTION BOXES 4.2.1 Environmental effects

PV array and PV sub-array junction boxes exposed to the environment shall be at least IP 54 compliant in accordance with AS 60529, and shall be UV resistant. 4.3 SWITCHING DEVICES 4.3.1 General

All switching devices shall comply with all the following requirements: (a) (b) (c)

Be rated for d.c. use.

Have a voltage rating equal to, or greater than, 1.2

×

V OC ARRAY.

Not have exposed expo sed metallic meta llic live liv e parts pa rts in the t he conn c onnecte ected d or disconn disc onnected ected state. stat e.

4.3.2 Non-load-breaking switches

In addition to the requirements of Clause 4.3.1, non-load-breaking switches shall have a current rating equal to, or greater than, their associated fault current protection device, or in the absence of such device, have a current rating equal to, or greater than, the required current carrying capacity of the circuit to which they are fitted. (Refer to Table 3.1) 4.3.3 Current breaking devices

In addition to the requirements of Clause 4.3.1, circuit breakers and any other load breaking disconnection devices used for protection and/or disconnecting means shall comply with all the following requirements:

* This Clause ceases to be part of this Standard on 31 May 2009. † This Clause becomes part of this Standard on 1 June 2009. COPYRIGHT

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(a)

(b) (c)

24

Not be polarit pola rity y sensitiv sens itivee (as fault faul t current cur rentss in a PV array arra y may flow flo w in the opposi opp osite te direction to normal operating currents) except for the PV array main switch in systems without batteries.

* d n a l a e Z w e N s d r a d n t a S t h g i r y p o C Be rated to interrupt full load and prospective fault currents from the PV array and any other connected power sources (e.g. batteries, generators and the grid).

When fault current protection is incorporated, the trip current shall be rated according to Clause 2.4.

4.4 PLUGS, SOCKET-OUTL ETS AND COUPLERS

Plugs, sockets-outlets and couplers shall comply with all the following requirements: (a) (b) (c) (d) (e) (f) (g) (h) (i) (j) (k)



×

V OC ARRAY .

Be protected from contact with live parts in both the connected and disconnected state (i.e. be shrouded). Have a current rating equal to, or greater than, the cable to which they are fitted. Require a deliberate force to disconnect.

Have a temperature rating suitable for their installation location. location. If multipolar, be polarized.

Comply with Class II.

If exposed to the environment, be rated for outdoor use, be UV resistant and be at least IP 54 compliant in accordance with AS 60529. Plugs shall not be able to enter socket-outlets of other voltage systems. Socket-outlets shall not accept plugs of other voltage systems.

Plugs and socket-outlets normally used for connection to a.c. mains power, as described in AS/NZS 3112, AS/NZS 3123 and IEC 60309-2, shall not be used in PV array wiring. 4.5 FUSES

4.5.1 Ratings

Fuses used in PV array installations installations shall comply with all the following requirements: (a) (b) (c)



×

V OC ARRAY.

Be rated to interrupt the full load and prospective fault currents from the PV array and any other connected power sources (e. g. batteries, generators and the grid).

NOTE : Wh en fus es are provide pro vided d for fault fau lt current curr ent prot ection ect ion,, the use of fus ed swi tch disconnectors (fuse-combination units) is recommended.

4.5.2 Fuse holders

Fuse holders shall comply with all the following requirements: (a)


(b)

Have a current rating equal to, or greater than, the corresponding fuse.

(c)

Provide a degree of protection not less than IP 20.

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×

V OC ARRAY.

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5

E A R T H I N G

5.1 GENERAL 5.1.1 General

The complete system configuration shall be considered when determining the earthing requirements of the PV array. Two separate issues shall be addressed— (a) (b)

earthing of the main current carrying conductors or the array (system earthing); and

earthing of exposed conductive parts for lightning protection and/or equipotential bonding (system bonding).

5.1.2 Point of connection of PV system earth

When the PV array is earthed, the connection to earth shall be made at a single point and this point shall be connected to the installation earth.

In systems without batteries, this connection point shall be between the PV array disconnection device and the power conditioning unit and as close as possible to the powerconditioning unit.

In systems containing batteries, this connection point shall be between the charge controller and the battery. This is to allow for interruption of any earth f ault current. 5.1.3 PV system earthing cable

If the PV array is earthed, the PV system earthing cable shall be sized to carry 1.25 × I SC SC ARRAY continuously, and comply with the provisions for earthing conductors set out in AS/NZS 3000 with respect to material and type, insulation and identification, installation, connections and aluminium conductors. 5.1.4 Bonding conductors

All PV array system bonding conductors shall comply with the material, type, insulation, identification, installation installation and connection requirements s pecified in AS/NZS 3000. 5.2 PV ARRAY SYSTEM EARTHING

In Table 5.1 several configurations of system earthing are considered. No consideration is given to earthing of exposed metallic parts (system bonding) as these are covered in later Clauses. The requirements of the manufacturer(s) of the PCU(s) to which the PV array is connected, shall be taken into account in determining the most appropriate system earthing arrangement.

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* d n a l a e Z w e N s d r a d n t a S t h g i r y p o C TABLE 5.1

PV SYSTEM EARTHING CONFIGURATION

PV array

Unearthed

Application circuit

Consequence on the status of the PV array

Unearthed d.c. load

Floating (refer to Figure 5.1)

Earthed d.c. load

Fixed to earth (refer Figure 5.2)

AC load connected via isolated PCU

Floating (refer Figure 5.3)

AC load connected via a non-isolated power conditioning unit

Fixed by the status of the neutral of the application circuit. (refer to Figure 5.4).

NO TE: If the a.c . v oltage olt age is LV the entire ent ire installation becomes LV (refer to AS/NZS 3000).

Unearthed d.c. load (refer to Figure 5.5)

Fixed to earth

Earthed d.c. load (refer to Figure 5.6)

Earthed 1

AC load connected via isolated PCU (refer to Figure 5.7) AC load connected via a non-isolated power conditioning unit (refer to Figure 5.8)

This configuration is dangerous and is NOT PERMITTED.

NO TES : 1

2

In simple earthed arrays either positive or negative conductors could be connected to the earth, but the preferred configuration is to earth the negative because connecting the positive to earth could result in corrosion of the earth electrode. In a centre tapped earthed PV array, the PV array is equally divided into two segments connected in series, and the midpoint is connected to earth. The ‘consequences on the status of the PV array’ column is not changed whether the array is centre tapped earthed or earthed on one pole.

FIGURE 5.1

UNEARTHED PV ARRAY AND UNEARTHED D.C. LOAD

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* d n a l a e Z w e N s d r a d n t a S t h g i r y p o C FIGURE 5.2

FIGURE 5.3

UNEARTHED PV ARRAY AND EARTHED D.C. LOAD(S)

UNEARTHED PV ARRAY CONNECTED TO A.C. LOAD VIA VI A A N I SOL ATE ATED D P CU

WARNING: THIS CONFIGURATION CAN BE VERY DANGEROUS.

NOTE : If the a.c. side sid e i s L V, the n th e whole who le instal ins tal lat ion (inclu (in cludin ding g t he PV arra y) has to be treate tre ated d as LV.

FIGURE 5.4

UNEARTHED PV ARRAY CONNECTED TO A.C. LOAD VIA VI A A NON- ISO LAT ED PCU

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* d n a l a e Z w e N s d r a d n t a S t h g i r y p o C FIGURE 5.5

FIGURE 5.6

FIGURE 5.7

EARTHED PV ARRAY AND UNEARTHED D.C. LOAD(S)

EARTHED PV ARRAY AND EARTHED D.C. LOAD(S)

EARTHED PV ARRAY CONNECTED TO A.C. LOAD VIA VI A A N I SOL ATE ATED D P CU

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* d n a l a e Z w e N s d r a d n t a S t h g i r y p o C WARNING: This configuration is NOT PERMITTED FIGURE 5.8

EARTHED PV ARRAY CONNECTED TO A.C. LOAD VI A A NON- ISO LAT ED PCU

5.3 EARTHING OF EXPOSED CONDUCTIVE CONDUCTIVE PARTS AND EQUIPOTENTIAL EQUIPOTENTIAL BONDING (SYSTEM BONDING)

There are three possible reasons for earthing exposed conductive parts of a PV array (system bonding). These are— (a) (b) (c)

equipotential bonding to avoid uneven potentials across an installation; protective earthing to provide a path for fault currents to flow; and

lightning protection.

An earth conductor may perform one or more of these functions in an installation. The dimensions and location of the conductor are very dependent on its function. 5.4 EQUIPMENT EARTHING

Equipment earthing refers to the bonding to earth of all exposed conductive parts and frames of the PV array including any structural metalwork. PV array frame earthing shall be installed in accordance with the PV array framework earthing decision tree in Figure 5.9. Exposed conductive parts of the PV array installation need not be earthed if the PV array installation complies with any of the following provisions: (a)

Double insulation (applies only if the PV array complies with all of (i), (ii) and (iii)):

(i)

General* PV modules complying complying with Class II requirements requirements in accordance accordance with the relevant product Standard.

NOTE : An A n I EC PV module mod ule saf ety Sta ndard ndar d t hat inc ludes lud es Cla ss II requ ire ments men ts is under unde r development (IEC 61730-1).

A1

(i)

General† PV modules complying complying with Class A requirements requirements in IEC 61730-1 and IEC 61730-2 or EN 61730-1 and EN 61730-2.

NOTE : Cl ass A module mod uless in IEC 61730-1 61730 -1 and IEC 61730 -2 and EN 617306 1730- 1 and EN 61730-2 are considered to meet the requirements for Class II equipment in AS/NZS 3100.

(ii)

Wiring outside junction boxes Where cables cables may come into contact with readily accessible PV array conductive parts, the cables shall be double insulated.

* This item ceases to be part of this Standard on 31 May 2009. † This item becomes part of this Standard on 1 June 2009. COPYRIGHT

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(iii)

(b) (c)

Wiring inside junction boxes Conductors within junction boxes having double insulation shall be protected, secured or insulated so that, if any one conductor becomes detached from its termination, neither the conductor nor its functional insulation can come into contact with accessible metal. The attachment of one conductor to another by tying, lacing, clipping or the like, in such a manner as to prevent either conductor coming into contact with accessible conductive parts if it becomes detached from its termination, shall be deemed to comply with this requirement.

* d n a l a e Z w e N s d r a d n t a S t h g i r y p o C Protection by electrical separation in accordance with AS/NZS 3000. Protection by SELV or PELV in accordance with AS/NZS 3000.

NOTE S: 1

To use this decision tree, either follow recommendations of AS/NZS 1768 or refer to local information such as the number of thunder days per year or other lightning characteristics. Assessment should include the relative position of the PV array to other buildings or structures, etc which may protect the PV array from lightning strikes.

2

A floating PV array is not directly connected to earth and is connected to an application circuit that is either unearthed or isolated from the PV array.

3

Framework includes all exposed conductive parts in this context. FIGURE 5.9

PV ARRAY FRAMEWORK EARTHING DECISION TREE

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6

M A R K I N G

A N D

S I G N S

6.1 GENERAL

All electric equipment shall be marked according to the requirements for marking in AS/NZS 3100. All signs required by Clauses 6.2 to 6.4 shall— (a) (b) (c) (d)

comply with AS 1319; be indelible;

be legible from at least 0.8 m unless otherwise specified in the relevant Clauses; and

be constructed and affixed to remain legible for the life of the equipment it is attached or related to.

NOTE : Examp Ex amp les of sig ns are given giv en in Appendi Appe ndix x G. G.

6.2 PV ARRAY AND PV SUB-ARRAY JUNCTION BOXES

A sign containing the text ‘SOLAR D.C.’ shall be attached to PV array and PV sub-array junction junc tion boxes. box es. 6.3 DISCONNECTION DEVICES 6.3.1 General

Disconnection devices shall be marked with an identification name or number in accordance with the PV array wiring diagram. All switches shall have the ON and OFF positions clearly indicated. 6.3.2 PV array main switch

The PV array main switch shall be provided with a sign affixed in a prom inent location with the following text: ‘PV ARRAY MAIN SWITCH’. 6.4 FIRE EMERGENCY INFORMATION

For PV arrays that are installed on buildings and have a rated power greater than 500 W or with V OC O C ARRAY greater than 50 V, a sign shall be installed next to the meter box (if one exists) and the building’s main switchboard. This sign shall state ‘Solar Array’ and provide information on the location of the PV array. This sign shall comply with AS 1319 and be legible from at least 1.5 m.

NOTE : In sma ll ins tal lation lat ions, s, the locati loc ation on inf orma tio n may be very ver y sim ple (e.g. (e. g. ‘on roof’); roof ’); in larger installations more information should be provided.

The sign shall also include the following PV array information: (a) (b)

Open circuit voltage.

Short circuit current.

NOTE : Appen A ppendix dix G co ntains nta ins an exampl exa mpl e of o f a sui table tab le sig n.

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7

D O C U M E N T A T I O N

7.1 DESIGN INFORMATION

The PV system designer should prepare the following documents and a copy should be handed to the PV system owner: (a) (b) (c)

A list of all alarms, both visual and audible, and the action that should be taken when the alarm is activated. A basic circuit diagram that includes the electrical ratings of the PV array, and the ratings of all fuses and circuit breakers. Recommended maintenance for the system.

NOTE : A gui de to ass ist in est abli shi ng mai nte nan nance ce requ iremen ire men ts and ass ociate oci ated d docu men tat ion for PV arrays is provided in Appendix H.

7.2 COMMISSIONING INFORMATION

A copy of relevant commissioning documents should be supplied to the customer.

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8

C O M M I S S I O N I N G

T E S T S

8.1 GENERAL

Commissioning tests are required to ensure that the PV array complies with the safety requirements of this Standard.

NOTE : Ot her commis com mis sioni si oni ng tes ts tha t coul d be carried carr ied out on larg e PV arra ys (> 10 1 0 kW) kW ) are indicated in Appendix I.

8.2 OPEN CIRCUIT VOLTAGE 8.2.1 General

This test is intended to ensure that wiring polarity and continuity of the PV array are correct. 8.2.2 Procedure

The open circuit voltage of every string shall be measured before connecting to other strings. All PV string open circuit voltages shall be within 5% variation; otherwise the connections shall be verified for polarity, continuity and possible faults and repaired. Once the verification is complete and satisfactory, the PV strings may be connected in parallel. The same procedure shall be carried out to verify PV sub-array open circuit voltages (if relevant) and PV array open circuit voltage before connecting the PV array to the PCU. NOTE S: 1

All measurements should be made when practicable under stable irradiance conditions. Conditions close to solar noon are preferable.

2

A guideline on open circuit voltage measurements for large PV arrays (> 20 strings) where the environmental conditions may change significantly during measurements is given in Appendix I.

3

Typically, this voltage should be the number of modules in the string times the voltage of one module.

8.3 SOLAR ISOLATION DEVICE TEST

The operation of the solar isolation device shall be verified, when present. The testing procedure shall be— (a)

(b)

with the PV array in normal operation under irradiance conditions greater than 500 W/m 2, operate the solar i solation device according to the instructions posted next to it and verify that the PV array has been disconnected from the system. operate the reset facility according to the installer’s instructions and verify that the PV array re-connects to the system.

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9.1

9

C A S E

S T U D I E S

GENERAL

To assist users of this Standard, Appendix J contains a set of case studies using the requirements of this Standard. The diagrams in Appendix J are examples only and are not exhaustive and numerous other configurations comply with this Standard. The diagrams in Appendix J do not contain full design information (e.g. cable size is not shown as no account has been made for voltage loss in the cables). 9.2

EXAMPLES

The examples shown in Appendix J cover the following cases:

Arr ay vol tage tag e 24 V

nominal

Features

Figure

Floating array without a battery:

-Case A: less than 4 strings

J1

-Case B: 4 or more strings

J2

Floating array with a battery:

48 V

nominal

-Case A: 3 sub-arrays, no fault current protection

J3

-Case B: 3 sub-arrays, no string fault current protection

J4

-Case C: multiple strings, no sub-arrays

J5

Earthed array, with battery, multiple strings, no sub-arrays

J6

Non-earthed array, without battery, grid connected

J7

Floating array, with battery:

-Case A: 2 sub-arrays, no fault current protection

J8

-Case B: 2 sub-arrays, no strings fault current protection

J9

-Case C: multiple strings, no sub-arrays, fault current protection

J10

Earthed array, with battery, multiple strings

J11

Low

Non-earthed array, without battery, grid connected:

voltage

-Case A: 3 or less strings, no sub-arrays

J12

-Case B: 4 or more strings, no sub-arrays

J13

Earthed array, without battery, grid connected, no sub-arrays

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* d n a l a e Z w e N s d r a d n t a S t h g i r y p o C APPENDIX A

CHARACTERISTICS OF PV ARRAYS AND SYSTEMS (Informative)

A1 PV ARRAYS

A1.1 d.c. vs. a.c. behaviour

One of the most important characteristics of direct current in relation to safety is that d.c. arcs, caused by switching or faults, are much more difficult to extinguish than a.c. arcs, because there are no zero crossing points in the current flow, as is the case for a.c. currents. This implies that all switchgear and fault current protection devices in the array need to be rated for use in d.c. circuits (d.c. switchgear is less readily available and its cost increases significantly as the d.c. operating voltage increases). A1.2 Series parallel configuration

To reduce mismatch and improve PV array yield, all PV strings within a PV array should be of the same technology and have the same number of series connected PV modules (see Figures 1.1 and 1.2). Also, all PV modules within the PV array should have similar rated electrical characteristics including short circuit current, open circuit voltage, maximum power current, maximum power voltage and rated power (all at STC). A1.3 Low fault levels

PV cells (and consequently PV arrays) behave like current sources under low impedance faults. Thus in PV arrays without battery storage, currents much greater than normal full load currents may not flow even under short circuit fault conditions, making short circuit detection difficult. Therefore, electric arcs can be formed in a PV array with fault currents that will not trip a fault current device. The implications for PV array design that arise from these characteristics are— (a) (b)

the chances of line-to-line faults, earth faults and inadvertent wire disconnections in the system need to be minimized; and

earth fault detection and disablement could be required as part of the system protection functions depending on the array size and location, to eliminate the risk of fire and/or electric shock.

A2 FAULT CURRENT PROTECTION A2.1 General

Fault currents due to short circuits in modules, in junction boxes or in module wiring or earth faults in array wiring, can result in overcurrent in a PV array. PV modules are current limited sources but because they can be connected in parallel and also connected to external sources (e.g. batteries), they can be subjected to overcurrents caused by either multiple parallel adjacent strings or from external sources or both. A2.2 Fault current protection rating

To allow for increased irradiance levels, the rating of fault current protection devices has to be higher than the short circuit current of the circuit to be protected. A 1.25 safety factor is considered appropriate for all Australian/New Zealand locations. As rated values of commercially available fuses and circuit breakers will not always match the 1.25 times short circuit current requirement allowance should be made to accommodate commercially available equipment.

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It is sugg ested that the fault current protection rating ( I ( I TRIP T RIP ) be as follows:

* d n a l a e Z w e N s d r a d n t a S t h g i r y p o C 1.25 × I SC SC ≤ I TRIP T RIP ≤ 2 × I SC SC

where

I SC SC

is the short circuit current of the relevant PV circuit at standard test conditions.

I TRIP T RIP

is the the rated rated value of the fault current current protection protection device.

A2.3 Number of strings

Fault current protection is irrelevant when there are only one to two strings in parallel, and there is no battery storage system, provided the PV modules are capable of withstanding a reverse current equal to their short circuit current.

If there are more than two strings in parallel then the maximum fault current that can flow in any one string is equal to the (number of strings –1) times the short circuit rating of one of the strings. Therefore if there are three or more parallel strings, the PV modules could be subjected to reverse currents of two or more times their nominal short circuit current. It is for this reason that the number of strings able to be connected in parallel without overcurrent protection in each string, is linked to the reverse current rating of a module (see Clause 2.4.1). A2.4 Battery storage

When battery storage is present, the battery is capable of overloading the PV array wiring and components if a fault occurs regardless of the number of parallel-connected strings. strings. The PV array must be protected against battery currents. A2.5 Diodes

Blocking diodes are not a reliable protection against reverse current because they often fail in short circuit mode. The use of blocking diodes is currently restricted to preventing battery discharge to an un-energized PV array at night. Their use should be avoided for other purposes because they are sources of f ailures and power loss. A2.6 Operating temperature

PV modules can operate well above ambient temperature under normal operating conditions. A common steady state temperature rise for silicon modules operating at the 2 maximum power point under 1 000 W/m solar irradiance and with adequate ventilation is 25 K. The temperature rise can be even higher when irradiance levels are greater than 1 000 W/m 2 and when modules have poor ventilation. The following two main requirements on the PV array design derive from this operating characteristic characteristic of PV modules: (a)

(b)

PV module efficiency reduces as their operating temperature increases (for cry stalline silicon solar cells the maximum power decreases between 0.4 and 0.5% per each degree K rise in operating temperature). Therefore adequate ventilation of the PV array should be a design goal, in order to ensure optimum performance for both modules and associated components. All the components and equipment that may be in direct contact or near the PV array (conductors, inverters, connectors, etc.) need to be capable of withstanding the expected maximum operating temperature of the PV array.

A3 PV SYSTEMS A3.1 Stand-alone photovoltaic photovoltaic (PV) systems with battery storage

These systems have the following characteristics: (a)

The use of batteries makes PV array fault current protection requirements more stringent as batteries can deliver very high fault currents within the array circuit. COPYRIGHT

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PV arrays in these systems tend to be extra low voltage (ELV).

* d n a l a e Z w e N s d r a d n t a S t h g i r y p o C Most stand-alone PV inverters on the market include an isolation transformer that provides separation of the PV array circuits from the a.c. load circuits. Both earthed and unearthed PV arrays may be used.

A3.2 Grid-connected photovoltaic (PV) systems

These systems have the following characteristics: (a) (b) (c)

Generally they do not use batteries for energy storage because the grid behaves as an infinite bus that can receive or supply power. PV arrays in these systems tend to be low voltage (LV).

A wide range of inverter topologies can be found on the market. Some of them include an isolation transformer, and some of them are transformerless; some of them require the PV array to be earthed and some of them require it not to be earthed.

A3.3 Solar water pumping system

These systems generally have the f ollowing features: (a) (b) (c)

PV array.

Pump and controller.

No batterie batt eries. s.

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* d n a l a e Z w e N s d r a d n t a S t h g i r y p o C APPENDIX B

MECHANICAL SAFETY RECOMMENDATIONS (Informative)

B1 GENERAL

Support structures and module mounting arrangements should comply with applicable building codes, regulations and Standards. B2 THERMAL ASPECTS

Provisions should be made in the mounting arrangement of PV modules to allow for the maximum expansion/contraction of the modules under expected operating temperatures, according to manufacturers recommendations. NOTE S: 1

Some types of PV modules degrade significantly in performance when inadequate ventilation causes the modules to operate at high temperature.

2

The operating temperature of PV modules can be significantly higher than ambient temperatures. A rough figure for well ventilated crystalline silicon is 25 K temperature difference at 1 000 W/m 2 and operating at the maximum power point.

B3 MECHANICAL LOADS ON PV STRUCTURES

The PV array support structures should comply with AS/NZS 1170.2.

NOTE : Suppor S uppor t s tructu tru ctures res are not usuall usu all y a prob lem for sma ll PV sys tem s.

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* d n a l a e Z w e N s d r a d n t a S t h g i r y p o C APPENDIX C

FAULT CURRENT ANALYSIS (Informative)

C1 GENERAL

In this appendix, the worst case PV array earth fault conditions are analysed for both earthed and floating PV arrays. The implications for fault current protection derived from the worst case fault current analysis are also discussed. The analyses are made for the case of PV strings with four series modules, however they are valid for any number of series connected PV modules. Also, the earth faults are considered to be zero impedance faults which is the case when the fault currents are the highest. C2 FLOATING PV ARRAYS

In floating PV arrays, there is no reference to earth, and therefore a single earth fault does not produce any fault currents (see Figures C1 and C2). What a single fault does produce is an earth reference for the PV array circuit, and a path for earth fault current in the event of a second earth fault or a person touching the live conductors and earth simultaneously.

FIGURE C1

FLOATING PV ARRAY OPERATING AT MAXIMUM POWER POINT

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* d n a l a e Z w e N s d r a d n t a S t h g i r y p o C FIGURE C2

FLOATING PV ARRAY WITH SINGLE EARTH FAULT

When a single earth fault develops, the PV array currents remain the same, if the system is not shut down and provided the PCU does not allow fault currents to pass through its power circuits from the load side to the PV array side. If there is electrical isolation between the PV array and a.c. loads, the system can continue operating in most cases but it becomes unsafe as the PV array is no longer floating, thus increasing the risk of electric shock and earth fault currents if a second earth fault occurs.

If a second fault dev elops in the PV array, the earth loop is closed allowing fault currents to flow in the PV array wiring (see Figure C3). Under the fault conditions of Figure C3, a three-module segment of string number 3 is short circuited, and the remaining PV modules in string number 3 are connected in parallel with strings 1 and 2. This would cause the PV array voltage to drop significantly, most likely causing the PCU to disconnect itself from the PV array, thus leaving the PV array open circuited.

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FLOATING PV ARRAY WITH DOUBLE EARTH FAULT – CASE I

The most important observations from the node analysis of this fault case are the following: (a)

(b)

(c) (d)

(e)

PV module M 3,1 is forward biased with a voltage that is larger than its open circuit voltage vol tage.. Thus the module mod ule is operatin oper ating g in the second seco nd quadran quad rantt of its I-V character char acteristi isticc (i.e. the current through it is negative and it is forced to dissipate the power delivered by PV strings 1 and 2).

As the voltage of strings 1 and 2 drops, their output current increases to approximately their short circuit value. If standard test conditions are assumed, the reverse current through module M 3,1 is approximately twice I SC MOD .

The current of the section of the string cable that connects module M 3,1 with the negative bus bar is also twice I SC MOD.

The reverse current through PV module M 3,1 and through the segment of the string cable that connects it to the negative bus bar would increase by approximately I SC MOD for each additional parallel PV string in the circuit.

If the faults occurred in opposite locations of the PV array (see Figure C4), then PV module M3,4 would be forced to dissipate the power delivered by strings 1 and 2 and the segment that connects it to the positive bus bar would be overloaded. This implies that fault current protection in unearthed PV arrays, when required, has to be in stalled in both positive and negative cables of the corresponding circuit.

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FLOATING PV ARRAY WITH WITH DOUBLE EARTH FAULT – CASE 2

C3 EARTHED PV ARRAYS

In earthed PV arrays, there is already a reference to earth and a path for earth fault currents and therefore a single earth fault, or a person touching an unearthed conductor and earth simultaneously, will produce earth fault currents to flow in the PV array. It should be noted that the worst-case earth fault scenario for earthed PV arrays is identical to that presented in Figure C4, the only difference is that the connection to earth of the negative conductor of the PV array cable is not a f ault but an intentional connection.

The node analysis and most of the observations made for the floating case hold true, except for the last one. In the earthed case, the PV string cable segments that connect to the negative busbar cannot be overloaded with one, or multiple, earth faults.

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* d n a l a e Z w e N s d r a d n t a S t h g i r y p o C APPENDIX D

EARTHING ISSUES (Informative)

D1 BACKGROUND

D1.1 Types of earthing

AS/NZS 3000 indicates that earthing in electrical installations is for protective and functional purposes. Protective earthing is intended to provide protection against indirect contact and fault current. Functional earthing is intended to ensure correct operation of electrical equipment or to permit reliable and proper functioning of electrical installations. installations. D1.2 Purpose of earthing

Earthing of electrical installations has the following purposes: (a) (b) (c) (d)

Minimize the risk of electric shock to persons using or servicing the electrical installation or associated equipment. Minimize the risk of fire due to fault conditions.

Reduce the risk of damage to equipment due to induced surges. Reduce possible electromagnetic interference.

D1.3 General earthing considerations in a PV system

In PV systems installations, earthing arrangements may involve— (a) (b)

earthing of the PV array output circuit (system earthing); and earthing of exposed conductive parts (system bonding).

D2 EARTHING OF EQUIPMENT CONDUCTIVE PARTS

Earthing of equipment conductive parts is a safety requirement of many international codes and Standards and it is thoroughly covered by AS/NZS 3000. The general requirement is that all exposed conductive parts, which are not intended to be energized in normal operation, be earthed as a protective measure against indirect contact. This is to ensure that all metallic parts remain at earth potential if a fault occurs in the insulation.

An exemption to earthing of conductive parts is permitted if the system components and installation comply with Class II requirements.

Even when PV installations installations are Class II com pliant, protective earthing of large area conductive metal parts, which are within arm’s reach, could be advisable. AS/NZS 3000 also allows for exemptions to protective earthing when the electrical systems fulfil the requirements of protection by electrical separation and when they fulfil the requirements of protection by SELV or PELV.

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PV arrays are frequently located high on buildings and therefore it may be advisable to earth PV frames and structures as they may provide a path to earth for surge currents induced by nearby lightning strikes. Earthing may also enable the operation of some protective devices, such as fault current and residual current devices, in the event of a fault to the frame of the PV array.


D3 EARTHING OF THE PV ARRAY (SYSTEM EARTH) D3.1 Options of PV array earthing

There are two basic options regarding PV array earthing— (a) (b)

not earthed, in which case the PV array voltage has no reference to earth. In this situation the PV array is also called a floating PV array.

earthed, in which case one of the output conductors of the PV array or the centre tapped in three wire d.c. system s is connected to earth.

Earthing of current carrying conductors in a PV array is a very controversial issue. In Europe system earthing is not required, and most PV systems there are not earthed. In the USA, the National Electrical Code requires all PV installations with system voltages above 50 V d.c. to be earthed. The main arguments for earthing or not earthing the PV array are ironically the same, personnel safety and fire safety, thus the controversy.

The selection of one of these two possible schemes has to do with functional and protective reasons. Either of the two approaches can achieve an acceptable level of safety in regards to electric shock, fire fire hazard, and equipment equipment safety. Each methodology has some advantages and disadvantages as explained in the following Clauses. D3.2 Typical earthing arrangements for PV arrays D3.2.1 Unearthed (floating) PV array

In the configuration shown in Figure D1, the PV array voltage is floating and no earth reference is established.

FIGURE D1

UNEARTHED (FLOATING) PV ARRAY

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D3.2.2 Negative earthed PV array


In the configuration shown in Figure D2, the PV array is connected to earth in the negative pole, and therefore the voltage to earth is well defined.

FIGURE D2

NEGATIVE EARTHED PV ARRAY

D3.2.3 Centre tapped earthed PV array

In the configuration shown in Figure D3, the PV array is usually divided into two segments with the same electrical characteristics (rated power, voltage and current) and the centrepoint connected to the neutral of an a.c. system (through a non-isolated inverter) which is connected to the MEN point and thus the voltages of sections of the array with respect to earth, are well defined.

FIGURE D3

CENTRE TAPPED EARTHED PV ARRAY

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D3.2.4 Centre tapped earthed PV array via capacitor


The configuration in Figure D4 provides a.c. coupling to the neutral of an a.c. system (through a non-isolated inverter) which is connected to the earth at the MEN point. The main difference fr om Figure D3 is that the centre tapped is capacitively coupled and therefore, there is no need to provide a separate centre connection from the PV array. The capacitive coupling provides a path for transient and a.c. currents but not for d.c current.

FIGURE D4

CENTRE TAPPED EARTHED PV ARRAY VIA CAPACITOR

D4 COMPARISON BETWEEN EARTHING SCHEMES D4.1 Earth fault behaviour D4.1.1 Floating systems

A single fault to earth does not cause a fault current, the PV array can continue operating, but the earth fault has to be detected and repaired for two reasons: (a)

(b)

The earth fault provides a reference to earth in a system which is supposed to be floating and, depending on the system voltage, this may pose a shock hazard to unaware service personnel. A second earth fault in a conductor at different potential will produce fault currents, increasing the risk of fire.

D4.1.2 Earthed system

A single earth fault can produce fault currents, creating a fire hazard. The PV array can not continue operating, the earth fault has to be detected and the fault current path disabled. A fault can be detected by measuring the current in the main earth. Interruption of the fault current can generally only be achieved by interrupting the main system earth (not the equipment earth). D4.1.3 Capacitively coupled earth systems

A single earth fault may not cause any d.c. fault currents to flow but this is very dependent on the inverter topology. The PV array may be able to continue operating, but the power conditioning unit may not operate correctly after a single earth fault. The earth fault has to be detected and repaired.

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D4.2 Electric shock hazard


D4.2.1 Floating systems

Generally speaking, the shock hazard from direct and indirect contact contact is low because the PV array voltage has no reference to earth; therefore there is no path for current in the event that a person touches a live conductor and an earthed metal part simultaneously. There are counter arguments that indicate possible shock hazards: (a)

(b)

PV arrays have some capacitance to earth. The value of the capacitance depends on the type of PV modules, the array size and the environmental conditions (e.g. salt mist in the PV array). This stray capacitance— (i)

could build a static charge capable of producing involuntary muscle reactions that could cause other injuries to service personnel; or

(ii)

may cause significant currents to flow if the array has any high frequency coupling (such as switching frequency) which is referenced in any way to earth.

PV arrays may have some leakage current to earth that provides an inadvertent reference to earth and a path for shock currents.

D4.2.2 Earthed systems

NOTE : Earth Ea rth ed sys tem s inc lude lud e capacit capa cit ively ive ly couple cou pled d sys tem s as the typica typ ica lly lar ge capa cit ance anc e could support dangerous shock currents for significant time periods.

Generally there is a high risk of electric shock because the PV array voltage is referenced to earth and earthed exposed metal parts are a very good path for shock currents. This risk can be reduced by using nonconductive junction boxes and enclosures. D4.3 Fire hazard

D4.3.1 Floating systems

Generally, the fire hazard from a single earth fault is low because two faults are required to produce a fault current that could produce an arc and consequently a fire. It is important however to detect, and at least install an alarm, so that if a single earth fault occurs, this fault may be corrected before a second fault develops. Another approach to the protection of floating systems is to make them ‘inherently safe’. This means providing Class II insulation throughout the installation, which may remove the need for protection systems, as the likelihood of a fault developing is very small. D4.3.2 Earthed systems

A single earth fault produces circulating fault current that can be difficult to interrupt unless the PV array earthing connection is opened; therefore the risk of fire is greater because there is a higher probability of d.c. arc formation in the event of a single earth fault. D4.3.3 Capacitively coupled earthed systems

Provided there is no failure of the coupling capacitors these are not generally capable of producing prolonged d.c. arcs in the event of a single earth fault.

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D5 OTHER CONSIDERATIONS CONSIDERATIONS


D5.1 Battery systems

In PV systems with batteries, it is important to protect the cabling and the PV modules from possible fault currents, which may flow from a connected battery system into the PV array. These fault currents can commonly be in excess of 1 000 A. To protect against possible damage from these currents, correctly rated overcurrent protective devices (e.g. fuses or circuit-breakers) need to be used between the PV array and the battery system. The overcurrent protection would normally be rated to carry 1.3 times the I SC SC of the PV array and be capable of interrupting the full prospective fault current provided by the battery system (if a short circuit was placed across the terminals of the PV array) and have a voltag vo ltagee ratin r ating g of o f at a t least le ast the full open -circuit -cir cuit voltage volt age of the PV arra a rray. y. D5.2 Non-isolated inverter systems for PV arrays

When non-isolated inverter systems are used in an installation a number of important issues with respect to safety and f ault protection need to be considered.

This can have an important influence on the earthing arrangement of the PV array itself. In general, in systems with isolated inverters, PV arrays can be earthed or unearthed. In systems with non-isolated inverters, careful consideration of manufacturer’s instructions and local Standards and guidelines become very important. In the simplest case, a non-isolated inverter used in a grid-connected system, which is referenced to earth on the a.c. side, may not be able to be earthed on the d.c. side without creating a fault situation. In some situations the installation of centre tapped earthed arrays or capacitively coupled earthed arrays will be possible and hence provide a reference to earth on the d.c. side.

A system with a non-isolated inverter and a PV array that is not earthed may have high frequency leakage currents through the stray capacitance of the PV array to earth. The magnitude of this current depends on the type of inverter internal configuration used. These high frequency currents may flow in surrounding metallic structures or may induce currents in persons coming into contact with the glass surface of a PV module. These currents may not be enough to cause immediate death by electrocution but may cause enough of a tingling sensation to cause a reflex reaction leading to a fall, which in turn may be fatal. The best earthing schemes for non-isolated PV arrays seem to be centre tapped earthing or neutral connection via capacitors. Both of these schemes avoid high frequency leakage currents and are compatible with grid earthing. The scheme that is used is very dependent on the topology and type of inverter used and manufacturer’s specifications should be consulted. D6 REFERENCES

1 2 3

ENERGIENED. Guidelines for the Electrical Installation of Grid Connected Photovo Pho tovoltai ltaicc (PV) ( PV) Systems Syst ems.. The Netherlands, 1998.

NATIONAL FIRE PROTECTION ASSOCIATION. ASSOCIATION. National Electrical Code: NEC 2002. Thomas 2002. Thomas Learning, 2001.

IEA PVPS T5-01. Utility Aspects of Grid Connected Photovoltaic Power Systems. Task V Report , December 1998.

4

CALAIS , M., , M., AGELIDIS , V. , V. and MEINHARDT M. Multilevel Converters for Single Phase Grid Connected Photovoltaic Systems: An Overview. Solar energy. 1999 vol. vol . 66, 6 6, No. 5, pp 325-33 325 -335. 5.

5

MEINHARDT M. et al. Multi String Converter with Reduced Specific Costs and Enhanced Functionality. Solar energy, energy , 2000, vol. 69, Nos. 1-6, pp 217-227. COPYRIGHT

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* d n a l a e Z w e N s d r a d n t a S t h g i r y p o C APPENDIX E

SUGGESTED METHODS OF DETECTION AND AUTOMATIC DISCONNECTION FOR EARTH FAULT PROTECTION (Informative)

E1 FLOATING SYSTEMS

In floating systems, it is possible to detect earth faults by measuring the resistance to earth of each active conductor with respect to earth. This can be achieved by means of an insulation monitor suitable for d.c. systems (see Figure 2.1). Some inverter manufacturers incorporate this feature in their products, in which case there is no need for an external insulation monitor.

E2 EARTHED SYSTEMS CONNECTED CONNECTED TO THE LOAD VIA AN ISOLATED POWER CONDITIONING SYSTEM

In earthed systems, earth leakage currents can be measured directly in the main earthing conductor of the PV array, or as the current imbalance between current carrying conductors caused by earth leakage currents. In order to achieve isolation of the PV array and disabling of the earth fault current path, the isolator must be located between the PV array and the earthing point of the PV array as shown in Figure 2.1. It is also recommended to install the earthing point, the isolation device and the current detection device as close as possible to the load or the PCU to provide protection of the whole PV array up to the end of the PV array cable (see Clause 5.1.2).

E3 GRID CONNECTED CONNECTED SYSTEMS CONNECTED CONNECTED TO THE LOAD VIA A NONNONISOLATED POWER CONDITIONING SYSTEM

Earth faults on the PV array and isolation of the grid can be achieved by means of a d.c. sensitive, or type A, RCD installed on the a.c. output of the PCU, as shown in Figure 2.1. When used, these devices must comply with AS/NZS 3190, AS/NZS 61008.1 or AS/NZS 61009.1.

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* d n a l a e Z w e N s d r a d n t a S t h g i r y p o C APPENDIX F

LIGHTNING/OVERVOLTAGE PROTECTION (Informative)

F1 LIGHTNING PROTECTION

A lightning protection system has the task of preventing severe damage caused by fire or mechanical destruction if a direct lightning strike occurs on a building or structure. Lightning protection systems consist of three essential components— (a) (b) (c)

an air termination system, consisting of metallic masts or rods of sufficient height to divert lightning currents through th eir structure;

a down conductor of sufficient cross-sectional area to conduct lightning currents to earth; and an earth termination system.

For ground mounted or freestanding PV arrays, the need for a lightning protection system should be assessed in accordance with AS/NZS 1768, and if required, it should be installed in compliance with that Standard.

The installation of a PV array on a building has a negligible effect on the probability of direct lightning strikes and therefore it does not necessarily imply that a lightning protection system should be installed if none is already present. However, if the physical characteristics or prominence of the building do change significantly due to the installation of the PV array, it is recommended that the need for a lightning protection system be assessed in accordance with AS/NZS 1768, and i f required, it should be installed in compliance with that Standard. If a lightning protection system is already installed on the building, it should be verified that the PV array and associated equipment are within the protection zone of the system in accordance with AS/NZS 1768. If the PV array is not within the protection zone of the existing lightning protection system, additional air termination(s) in accordance with AS/NZS 1768 should be provided.

When a PV array is protected by a lightning protection system, the metal structure of the PV array should be bonded to the lightning protection system, unless the minimum safety clearances as specified in AS/NZS 1768 can be achieved. F2 OVERVOLTAG E PROTECTION F2.1 Equipotential bonding

Damage caused by overvoltage is due to the failure of the insulation between active components or between active components and earth. The intention of overvoltage protection is to equalize all exposed metallic sections of an installation to a common potential during an overvoltage and to prevent insulation flashover. Equipotential bonding is therefore a most i mportant overvoltage protection measure. To avoid the formation of wiring loops between earthed conductors and d.c. cabling, equipotential bonding conductors should run parallel to, and as close as possible to, the d.c. cabling. It is also recommended that the bonding conductor is branched to run parallel with all the d.c. cabling branches.

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F2.2 Wiring loops


To reduce the magnitude of lightning induced overvoltages, the PV array wiring should be laid in such a way that the area of conductive loops is minimized (see example in Figure 3.1). F2.3 Surge arresters F2.3.1 General guide

Surge arresters are a very common method of protecting electrical systems and equipment against overvoltages. When these devices are used, the recommendations of AS/NZS 1768 should be observed. Overvoltage protection with surge arresters should be provided when the PV power system meets any of the following criteria— (a) (b) (c)

supply of critical loads (e.g. telecommunication repeater stations); stations); or the PV array has a rated capacity greater than 500 W; or

the PV array is protected with a lightning protection system.

Many commercial PV inverters and charge controllers are fitted with surge arresters on the PV input terminals, and this should be considered when specifying the overvoltage protection of the PV array. F2.3.2 Selection

The preferred type of surge arresters for overvoltage protection of PV arrays are metaloxide varistors (MOVs). These devices are voltage dependent resistors that have a high resistance at normal circuit operating voltage, but their resistance reduces with increased surge voltage and current. Spark gap devices are not suitable for use in d.c. circuits as once conducting, they will not stop conducting until the voltage across their terminals is typically less than 30 V. Because the performance of MOVs deteriorates with repeated operation (their resistance decreases), it is usual to allow a high safety margin in the selection of the device rating in lightning prone areas. Alternatively, facilities should be provided to give an indication of device failure. The use of thermally monitored MOVs is recommended to avoid excessive system losses and troubleshooting time caused by device failure. F2.3.3 Usage and installation

The following recommendations should be observed for the utilization and connection of surge arresters to protect PV arrays: (a)

(b) (c)

A surge arrester should be connected between each active conductor of the PV array cable and earth. Differential mode protection is not required unless the voltage protection level (V P) of the surge arresters is greater than 1 100 V.

In subdivided PV arrays, the provision of surge arresters in both active conductors of each PV sub-array cable is recommended.

The cable distance between the surge arresters and the PV modules s hould not exceed 15 m.

(d)

Where the PV array cable exceeds 20 m, surge arresters should be connected at each end of the cable, one set next to the PV array, and the other one next to the power conditioning unit. In this case, it should be verified that the power conditioning unit is already fitted with surge arresters.

(e)

Junction boxes are a good place to install the surge arresters. Care should be taken to connect them on the PV module side of any disconnecting devices.

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(f) (g)

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The common terminal of surge arresters should be connected to both the conductive PV array frames and structures and to the equipotential bonding system.

* d n a l a e Z w e N s d r a d n t a S t h g i r y p o C Cables for connecting surge arresters should be as short as possible and avoid loops and sharp directional changes

F2.3.4 Recommended specifications for surge arresters

The recommended specifications for surge arresters to protect PV arrays from overvoltages caused by indirect lightning strikes are as follows: (refer to list of parameters for surge arrester selection in IEC 61643-12): (a) (b) (c)

Maximum continuous operating voltage (V ( V C): V C > 1.3 Maximum discharge current ( I max ): I max max ): I max

≥ 5

×

V OC O C STC GEN.

kA.

Voltage protection level ( V p): V C < V p < 1.1 kV.

F2.4 Shielding

When the PV array frame is bonded to a lightning protection system, the PV array cable should be shielded by one of the following methods, and the shielding conductor should be connected to earth at both ends— (a) (b) (c)

with a metallic cable armour or shield with an equivalent cross-sectional area of 6 m m2 of copper; or with a metallic conduit suitable as a bonding conductor; or

2

with an equipotential bonding conductor with a cross-sectional area of at least 6 mm .

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* d n a l a e Z w e N s d r a d n t a S t h g i r y p o C APPENDIX G

EXAMPLES OF SIGNS (Informative)

This appendix provides examples of appropriate signs as specified in Section 6.

NOTE : The exa mpl es are for the case cas e study st udy of Fig ure J13 in Append App endix ix J, whe re the arra y has an automatically operated grid protection device on loss of utility voltage.

Colour: Black on white

FIGURE G1 EXAMPLE OF SIGN REQUIRED ON PV ARRAY JUNCTION BOX (CLAUSE 6.2)


FIGURE G2

EXAMPLE OF SIGN REQUIRED ADJACENT TO PV ARRAY MAIN SWITCH (CLAUSE 6.3.2.)

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* d n a l a e Z w e N s d r a d n t a S t h g i r y p o C Colour: White on red

FIGURE G3

EXAMPLE OF FIRE EMERGENCY INFORMATION SIGN REQUIRED ON THE MAIN SWITCHBOARD (CLAUSE 6.4)


FIGURE G4

EXAMPLE OF SHUTDOWN PROCEDURE

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* d n a l a e Z w e N s d r a d n t a S t h g i r y p o C APPENDIX H

MAINTENANCE REQUIREMENTS (Informative)

H1 SAFETY

Attention should be given in the maintenance procedures to the following safety requirements: (a) (b) (c) (d) (e)

Emergency shutdown procedure. Obey all warning signs.

Shut system down and interrupt PV array currents according to the manual shutdown procedure. Split strings into extra low voltage sections (if relevant).

Warn of any live parts that cannot be de-energized during daylight.

H2 PERIODIC MAINTENANCE

The following maintenance activities could be considered for inclusions in the maintenance procedures, according to the location, size and design of the PV array: (a) (b) (c) (d) (e) (f) (g) (h) (i) (j) (k) (l)

Safety warnings and manufacturers recommendations.

Cleaning of the PV array might be periodically required in locations where it is likely to collect dust or other shading materials.

Periodic inspections should be carried out to check wiring integrity, electrical connections, corrosion and mechanical protection of wiring. Verify open circuit voltage and short circuit current values. Verify functioning of earth fault protection (if relevant). Verify operation of tracking systems (if relevant). Measure I-V characteristics (if possible).

Perform seasonal PV array tilt adjustment (if relevant). Check PV array mounting structure(s). Test operation of switches regularly.

Check for module defects (fracture, moisture penetration, browning, etc.). Verify status of surge arrestors (if relevant).

A sample maintenance schedule is shown in Table H1.

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TABLE H1

* d n a l a e Z w e N s d r a d n t a S t h g i r y p o C SAMPLE MAINTENANCE SCHEDULE

Sub-system or component

Maintenance action

1)

2)

Freq .

Remarks

Verify:

Site

(a)

(b)

Cleanliness (accumulation of debris around and/or under array). No shading of array.

Verify cleanliness (accumulation of dust or fungus on array)

Clean site as required.

Quarterly

Trim trees, if required.

Quarterly

Check for visual defects including—

PV modules

(a) fractures; (b) browning; (c) moisture penetration; and (d) frame corrosion. Inspect junction boxes for— (a) tightness of connections; (b) water accumulation/build-up; (c) integrity of lid seals; (d) integrity of cable entrance, glands and/or conduit sealing; and (e) integrity of clamping devices.

Clean if necessary

1 Yr

Modules with visual defects should be further inspected for performance and safety to determine the need for replacement

1 Yr

Any defective seals, clamps and by pass diodes should be replaced

5 Yr

Any damaged conduit

Verify bypass diodes.

Verify mechanical integrity of conduits.

should be replaced

Verify insulation integrity of cables installed

5 Yr

without conduit.

Any damaged cable should

be replaced

Check junction boxes for—

Wiring installation

(a) (b) (c) (d) (e)

tightness of connections; water accumulation/build-up; integrity of lid seals; integrity of cable entrance and/or conduit sealing; and integrity of clamping devices

1 Yr

Any defective seals, clamps blocking diodes and surge arresters should be replaced

Verify: (i)

blocking diodes

(ii)

surge arresters for degradation

Check earthing connections for— (a) (b)

Electrical characteristics

Protective devices

Mounting structures

tightness of connections; and corrosion.

1 Yr

Measure open circuit voltages

1 Yr

Measure short circuit currents

1 Yr

Verify integrity of fuses

1 Yr

Verify operation of CBs and RCDs

1 Yr

Verify operation of earth fault protection system

1 Yr

Verify operation of solar array isolation device

1 Yr

Verify tightness and integrity of bolts and other fastening devices

1 Yr

Inspect for corrosion

5 Yr

1)

This list of items is not exhaustive but are examples only.

2)

Values for frequency are examples. Frequency will be site dependent. COPYRIGHT

According to Clause 8.2

According to Paragraph I7

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H3 OPERATION AND MAINTENANCE PROCEDURES


Operation and maintenance procedures should include the following: (a)

(b) (c) (d)

A short description of the function and operation of all installed equipment. More detailed information should be available from the manufacturer’s documentation (see Item (d).

Emergency and maintenance shutdown procedures.

Periodic maintenance requirements including procedures and schedule.

Equipment manufacturer’s documentation (data sheets, handbooks, etc.) for all equipment supplied.

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* d n a l a e Z w e N s d r a d n t a S t h g i r y p o C APPENDIX I

ADDITIONAL COMMISSIONING TESTS (Informative)

I1 GENERAL

The commissioning tests outlined in this appendix could be used as part of the tender process for large PV arrays (>10 kW). I2 OPEN CIRCUIT VOLTAGE MEASUREMENTS I2.1 General

This procedure gives a guide to open circuit voltage measurements in PV arrays with a large number of PV strings (20 or more) and where the environmental conditions and PV array operating conditions are likely to change significantly during the measurements, due to the time required for each measurement. I2.2 Procedure

Before closing any switches and installing fuses, the open circuit voltage of each PV string should be measured. The measured values should be compared with the expected value. Where required temperature corrections should be applied according to manufacturer’s specification. Module temperature should be measured on the back of one of the central modules of each string. Voltage measurements should be made with an accuracy of ±2%; temperature measurements should have an accuracy of ±1°C. NOTE S: 1

Voltages less than the expected value may indicate one or more modules connected with the wrong polarity, or a partial line-to-line or line-to-ground fault due to insulation damage and/or water accumulation inside conduits.

2

High voltage readings are usually the result of wiring errors.

The measured open circuit voltage of each PV string should be within 3% of the expected value; val ue; if there ther e is a larg er differen diff erence, ce, the PV stri ng wiring wiri ng should shou ld be checked chec ked (see (se e Notes Note s 1 and 2) and the wiring corrected. Once every string has been verified, and if necessary corrected, they should be parallel connected via switching devices and/or by installing fuse elements. I2.3 PV Arrays and sub-arrays measurement

Once the installation of the PV strings have been verified and the strings have been connected in parallel, the open circuit voltage of each PV sub array (if relevant) and of the PV array should be measured using the same procedure as with PV strings.

The measured values should be within 3% of the expected value, otherwise the wiring should be checked and corrected if necessary. In addition to wrong polarity and insulation faults, defective surge protection devices could be the cause of lower than expected voltage readings in the case of PV arrays and sub-arrays.

NOTE : Li ne- to- grou nd voltag vol tages es in bipo lar arra ys sho uld be rela tivel ti vely y balanc bal anced ed around aro und zero wit h one line above zero (positive) and one line below zero (negative).

I2.4 Records

The inspecting personnel should prepare a report that includes voltage and temperature measurements, and states the condition of the PV array wiring after the test, including any repairs and corrections carried out as a result of the inspections.

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I3 SHORT CIRCUIT CURRENT


I3.1 General

The PV array short circuit current should be measured using the procedure in Paragraphs I3.2 and I3.3 to further verify that there are no faults within the PV array wiring and that the PV modules and other components are in good condition. I3.2 Procedure

The measured values of short circuit current of each PV string, PV sub-array (if relevant) and of the PV module should be compared with the expected short circuit current value calculated with the following equation. Current measurements should be made with an accuracy of 2%. Irradiance measurements should be made simultaneously with each short circuit current measurement; a suitable pyranometer or reference cell should be used to determine in-plane irradiance. I SC S C EXPECTED = n

( G I/1000) × 0.95 × I SC S C MOD × (G

where

I SC S C EXPECTED

=

Expected Expected short circuit circuit current current of the segment segment under test (A)

n

=

Number of parall parallel el connec connected ted strings strings in the the segment segment under under test

G I

=

Plan Planee of arra array y irra irradi dian ance ce (W (W/m /m )

0.95 0.95

=

Factor Factor to accou account nt for mismat mismatch ch

2

NOTE S: 1

I SC of

the PV array or array segment should be measured with the array not shaded and under clear sky with noontime conditions.

2

The short circuit current of crystalline silicon-based PV devices is relatively insensitive to variations in ambient temperature over a wide operating range ( −10 to 40°C), increasing slightly with increasing temperature.

3

Other PV cell technologies may be more sensitive to temperature or to other conditions such as spectral content. Additional constraints may have to be observed or modifications made to the above equation.

4

Some PV module technologies have a settling time when the electrical output parameters are significantly higher than the nominal values. This should be taken into account and the above equation modified accordingly.

5

Low I SC measurements can indicate the presence of circulating ground fault currents in the array due to multiple ground faults or shading.

6

Higher than expected measurements can indicate an array configuration other than expected or increased irradiance on the array not being sensed by the pyranometer.

The measured values should be within 5% of the expected value; otherwise the wiring should be checked and corrected if necessary. In addition to insulation faults, defective surge protection devices could be the cause of lower than expected current readings in the case of PV arrays and sub-arrays. I3.3 Records

The inspecting personnel should prepare a report that includes the current and irradiance measurements, stating the condition of the PV array wiring after the test, including any repairs and corrections carried out as a result of the inspections. I4 INFRARED SCAN

A camera that is sensitive to infrared (IR) radiation can be used to detect areas of nonuniform temperature. Temperature non-uniformities may indicate problems within the array.

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I5 PV ARRAY TRACKER OPERATION TEST (IF RELEVANT)


Verify the operation and performance of array tracking mechanisms in accordance with manufacturer specifications and system requirements. I6 PV ARRAY I-V CURVE

I-V curves of the PV array are a very good indication of the correct installation and operation of the PV array components. Measurements can be made with programmable loads or capacitive loads. Measurements should be made in accordance with IEC 61829. The Standard contains a procedure to extrapolate the results to STC conditions for crystalline silicon PV arrays. For other module technologies only the actual measurements should be reported and the test conditions specified. I7 EARTH FAULT PROTECTION PROTECTION TEST (IF RELEVANT) I7.1 General

When present, the earth fault protection system operation and calibration should be v erified. I7.2 Measurements

Current measurements should be made to an accuracy of

±2%.

I7.3 Procedure

(a) (b) (c) (d)

(e)

(f)

2

Establish that there is an irradiance level of 500 W/m or greater, preferably under clear sky conditions. Set the PV system in normal operation mode.

Using a variable resistive load, simulate a high impedance earth fault on one of the unearthed conductors of the PV array cable.

Decrease the resistance gradually until the earth fault protection device detects the fault. Record earth fault current level and/or resistance that trigger the earth fault protection device.

If the measured values do not comply with those given in Clause 2.6.2 within 5% deviations, make the required adjustment to the earth fault protection system until these values are met. Carry out the procedure for both the positive and negative conductors with unearthed PV arrays.

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* d n a l a e Z w e N s d r a d n t a S t h g i r y p o C APPENDIX J

CASE STUDIES DIAGRAMS (Informative)

J1 GENERAL

This Appendix contains examples of common configurations for installing PV arrays. It should be noted that the examples shown in this Appendix are not exhaustive and that many other configurations are acceptable. J2 NOTES ON CASE STUDIES

(a) (b)

(c)

For the formulas to determine the minimum current carrying capacity of cables see Clause 3.4 and Table 3.1.

For the determination of fault current protection ratings and location see Clause 2.4. The fault current protection ratings selected in the case studies are the smallest ones likely to be commer cially available within the allowable range.

All these case studies are based on crystalline silicon PV modules where I MOD M OD REVERSE is typically 2.6 × I SC . Thus n is equal to 3 (see Table 2.1). SC MOD p

FIGURE J1

24 V NOMINAL, FLOATING ARRAY WITHOUT BATTERY CASE A: LESS THAN 4 STRINGS

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* d n a l a e Z w e N s d r a d n t a S t h g i r y p o C FIGURE J2

24 V NOMINAL, FLOATING ARRAY WITHOUT BATTERY CASE B: 4 OR MORE STRINGS

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* d n a l a e Z w e N s d r a d n t a S t h g i r y p o C FIGURE J3 24 V NOMINAL, FLOATING ARRAY WITH BATTERY CASE A: 3 SUB-ARRAYS, NO FAULT CURRENT PROTECTION

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* d n a l a e Z w e N s d r a d n t a S t h g i r y p o C FIGURE J4 24 V NOMINAL, FLOATING ARRAY WITH BATTERY CASE B: 3 SUB-ARRAYS, NO STRING FAULT CURRENT PROTECION

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* d n a l a e Z w e N s d r a d n t a S t h g i r y p o C FIGURE J5 24 V NOMINAL, FLOATING ARRAY WITH BATTERY CASE C: MULTIPLE STRINGS, NO SUB-ARRAYS

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24 VOLT NOMINAL, EARTHED SYSTEM WITH BATTERY, MULTIPLE STRINGS, NO SUB-ARRAYS

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48 V NOMINAL, NON-EARTHED NON-EARTHED ARRAY WITHOUT BATTERY, GRID CONNECTED

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NOTE : In thi s case c ase study, stu dy, the str ing cabl es need a high h igh er c urrent urre nt rat ing than tha n t he sub -array -arr ay cabl es.

FIGURE J8 48 V NOMINAL, FLOATING ARRAY WITH BATTERY CASE A: 2 SUB-ARRAYS, NO FAULT CURRENT PROTECTION

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NOTE : In thi s case c ase study, stu dy, the str ing cabl es need a high h igh er c urrent urre nt rat ing than tha n t he sub -array -arr ay cabl es.

FIGURE J9 48 V NOMINAL, FLOATING ARRAY WITH BATTERY CASE B: 2 SUB-ARRAYS, NO STRINGS FAULT CURRENT PROTECTION

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FIGURE J10 48 V NOMINAL, FLOATING ARRAY WITH BATTERY CASE C: MULTIPLE STRINGS, NO SUB-ARRAYS, FAULT CURRENT PROTECTION

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FIGURE J11

48 V NOMINAL, EARTHED ARRAY WITH BATTERY, MULTIPLE STRINGS

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FIGURE J12

LV ARRAY, GRID-CONNECTED WITH NO SYSTEM EARTHING OF PV CASE A: 3 OR LESS STRINGS, NO SUB-ARRAYS

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FIGURE J13

LV ARRAY, GRID-CONNECTED WITH NO SYSTEM EARTHING OF PV CASE B : 4 OR MORE STRINGS, NO SUB-ARRAYS

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FIGURE J14

LV, EARTHED ARRAY, GRID CONNECTED, MULTIPLE STRINGS, NO SUB-ARRAYS

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* d n a l a e Z w e N s d r a d n t a S t h g i r y p o C AMENDMENT CONTROL SHEET AS/NZS 5033:2005

Amendment Amendment No. 1 (2009)

REVISED TEXT

SUMMARY: This

Amendment applies to the Preface and Clauses 1.1, 1.3, 4.1.2 and 5.4(a)(i).

Published on 28 January 2009.

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* d n a l a e Z w e N s d r a d n t a S t h g i r y p o C NOT ES



Standards Australia

Standards Australia is an independent company, limited by guarantee, which prepares and publishes most of the voluntary technical and commercial standards used in Australia. These standards are

developed through an open process of consultation and consensus, in which all interested parties are invited to participate. Through a Memorandum of Understanding with the Commonwealth

government, Standards Australia is recognized as Australia’s peak national standards body.

Standards New Zealand

The first national Standards organization was created in New Zealand in 1932. The Standards Council of New Zealand is the national authority responsible for the production of Standards.

Standards New Zealand is the trading arm of the Standards Council established under the Standards Act 198 8.

Australian/New Zealand Standards

Under a Memorandum of Understanding between Standards Australia and Standards New Zealand, Austra Aus tralia lia n/N ew Zealan Zea lan d S tandar tan dards ds are prepar pre par ed by committ comm itt ees of exp ert s from f rom ind ustry, ust ry,

governments, consumers and other sectors. The requirements or recommendations contained in published Standards are a consensus of the views of representative interests and also take

account of comments received from other sources. They reflect the latest scientific and industry

experience. Australian/New Zealand Standards are kept under continuous review after publication and are updated regularly to take account of changing technology.

International Involvement

Standards Australia and Standards New Zealand are responsible for ensuring that the Australian

and New Zealand viewpoints are considered in the formulation of international Standards and that

the latest international experience is incorporated in national and Joint Standards. This role is vital in assisting local industry to compete in international markets. Both organizations are the national members of ISO (the International Organization for Standardization) and IEC (the International Electrotechnical Commission).

Visit our web sites

www.s ww w.stand tandards. ards.org. org.au au www.s ww w.stand tandards. ards.com. com.au au

www.s ww w.stand tandards. ards.co.nz co.nz

GPO Box 476 Sydne Sydneyy NSW 2001

Level 10 Radio New Zealand House

Phone (02)

155 The Terrace Wellington 6001

9237 6000

Fax (02) 9237 6010 Email

[email protected] [email protected]

Phone (04)

498 5990

www.standards.org.au Internet www.standards.org.au

Fax (04)

SAI Global Customer Service

Customer Services (04)

Phone

13 12 42

Fax 1300

65 49 49

Email [email protected]

ISBN 0 7337 6699 4

(Private Bag 2439 Wellington 6020)

498 5994 498 5991

Information Service (04)

498 5992

[email protected] Email [email protected] Internet www.standards.co.nz

Printed in Australia

NZS/ AS 5033

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