International standard IEC 60947-2 Low voltage switchgear
DBTP83-Fr-03/99
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Part 2: Circuit-breakers
EC 60947-2
Contents n I. General
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n 2. Definitions
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n 3. Circuit-breaker characteristics
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n 4. Constructional requirements
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n 5. Specific points (appendices)
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n 6. Tests
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n 7. Conclusion
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EC 60947-2
General
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Standard IEC 60947-2 n Came into force in 1989 n Takes into account the circuit-breaker main technological upgrades Standard IEC 60947-2 n Is internationally recognized and approved
CSA
IEC
UL
IEC
IEC IEC
JIS/IEC
IEC IEC
and is applied in the majority of countries (> 100)
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General constitution Standard IEC 60947-2 is part of a set of 7 standards characterizing low voltage switchgear E55231
EC 60947-2
IEC 60 947-2
or
Circuit-breakers IEC 60947
IEC 60947-1
IEC 60 947-3
or
IEC 60 947-4-1
or
Contactors and starters
Switches
General rules IEC 60 947-6-2
Control and connection devices
or
IEC 60 947-7-1
or
IEC 60 947-4-2
or
Dimmers and starters
… ...
Terminal block
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General
EC 60947-2
The scope
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« Standard IEC 60947-2 applies to circuit-breakers, the main contacts of which are intended to be connected to circuits, the rated voltage of which does not in exceed 1000 V AC or 1500 DC; … »
The standard applies to circuit-breakers intended for use by experienced operators.
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General
EC 60947-2
The scope
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Standard IEC 60947-2 contains additional specifications for: n Circuit-breakers suitable for isolation n Residual current devices (appendix B) n Circuit-breakers with electronic protection (appendices J and F) n Circuit-breakers for IT systems (appendix H)
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General
EC 60947-2
Standard IEC 60947-2 defines n The circuit-breaker classification o according to utilization category A or B o according to design type air circuit-breaker, moulded case circuit-breaker
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n The circuit-breaker mechanical and electrical data: size, trip unit, etc.
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Definitions
EC 60947-2
Circuit-breaker classification
Utilization category A Circuit-breaker not specifically intended for discrimination n Without an intentional short-time delay
Utilization category B Circuit-breaker specifically intended for discrimination: n With intentional short-time delay (adjustable) n With short time withstand current E55235
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n Without short time withstand current
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EC 60947-2
Definitions Terminology / Vocabulary Extract from appendix K of standard IEC 60947-2 Characteristics voltage current
short-circuit
trip unit
Ue Ui Uimp In Ith Ithe Icm Icu Ics Icw Ir 1.05 x Ir 1.30 x Ir Isd Ii
Rated operational voltage Rated insulation voltage Rated impulse withstand voltage Rated current Conventional free-air thermal current Conventional enclosed thermal current Rated short-circuit making capacity Rated ultimate short-circuit breaking capacity Rated service short-circuit breaking capacity Rated short-time withstand current Adjustable overload setting current Conventional non-tripping current Conventional tripping current Short time delay tripping setting current Instantaneous tripping setting current
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Circuit-breaker characteristics Overload withstand E55236
EC 60947-2
In (in A rms) = rated current n Maximum uninterrupted current withstood at ambient temperature, given without abnormal temperature rise Ir (in A rms) = adjustable overload setting current n Ir depends on In n Ir characterizes the overload protection
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Circuit-breaker characteristics Short-circuit withstand E55237
EC 60947-2
Icu (kA rms) = rated ultimate short-circuit breaking capacity n This performance expresses the maximum value of the short-circuit current that can be broken by the circuit-breaker
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Circuit-breaker characteristics Short-circuit withstand Standard IEC 60947-2 introduces a new important performance Ics (as a % of Icu) = rated service short-circuit breaking capacity
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EC 60947-2
n This performance expresses the suitability of a circuit-breaker to ensure fully normal service after breaking this current 3 times n Normal ratio between Ics and Icu Utilization category A % of Icu 25 50 75 100
Utilization category B % of Icu 50 75 100
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Circuit-breaker characteristics Short-circuit withstand Standard IEC 60947-2 introduces a new performance for category B circuit-breakers
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EC 60947-2
Icw (in kA rms) = rated short-time withstand current n Icw is the maximum short-circuit current that a circuit-breaker can withstand for a short duration ∆t without deterioration of these characteristics n ICW must be at least equal to 12 I n or 5 kA for I n ≤2500 A 30 kA for I n > 2500 A n The standardized delay time ∆t is: 0.05 - 0.1 - 0.25 - 0.5 or 1s
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Constructional requirements
EC 60947-2
Isolation co-ordination The circuit-breaker, as a safety device, must be able to withstand n Network overvoltages this suitability is characterized by the withstand to the conventional dielectric test at 2 Ui + 1000 - 1 min at power frequency
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n Impulse voltages ( «lightning stroke» simulation) this suitability is characterized by the withstand to the 1.2/ 50 µs impulse voltage test of value Uimp
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EC 60947-2
Constructional requirements Isolation co-ordination Uimp (kV peak) = rated impulse withstand voltage
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Characterization of Uimp n Depends on the LV network voltage n Depends on the position of the circuit-breaker in the LV network n Depends on altitude: Uimp must be valid up to 2000 m tests carried out at +23 % of value
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Constructional requirements Isolation co-ordination Characterization of Uimp Nominal installation voltage
Applications E55243
EC 60947-2
at the origin of the installation/MSB
on the distribution and final circuits
at load level
230/400 V
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4
2.5
400/690 V
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6
4
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EC 60947-2
een upstream stream
Constructional requirements Isolation co-ordination Industrial circuit-breaker Uimp = 8 kV n Tests to be considered o Uimp + 23 % = 9.8 kV o standard industrial circuit-breakers and those suitable for isolation
Application of impulse voltage Phase-to-phase Up-to-downstream contacts open Phase-to-earth
Impulse voltage value Breakers Disconnector Breakers 9.8 kV 9.8 kV 12.3 kV (*) 9.8 kV
9.8 kV
(*) 14.7 kV for front face class II circuit-breaker as per IEC 61 140
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EC 60947-2
Constructional requirements Circuit-breaker suitable for isolation Test of isolation suitability n 3 tests designed to ensure users that a device «suitable for isolation» is not dangerous o in open position...
- even after having eliminated a short-circuit up to Icu - even in the event of overvoltage on the network ... or in closed position o cannot be declared «open» and/or « padlockable »
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EC 60947-2
Constructional requirements Circuit-breaker suitable for isolation
Class ll enclosure Class ll front face
class ll
al ruggedness
Leakage current measurement test at 110 % of maximum utilization voltage Ue n New device, leakage current < 0.5 mA per pole, n After breaking at Ics, leakage current < 2 mA per pole, n After durability tests, leakage current < 2 mA per pole, n After breaking at Icu, leakage current < 6 mA per pole Impulse voltage withstand n Uimp = 12 kV (instead of 9.8 kV) between the inlet and the outlet of the open device (*) 14.7 kV for front face class II circuit-breaker as per IEC 61 140
Mechanical ruggedness test n Circuit-breaker with a pole held in closed position must not be indicated «open» and/or «lockable» by padlock. Padlockable in « open » position
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Constructional requirements
EC 60947-2
Circuit-breaker/isolator Marking
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n A circuit-breaker that is «suitable for isolation» will display the circuitbreaker/isolator symbol on its front face
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EC 60947-2
Specific points (appendix A) Standard IEC 60947-2 recognizes and defines circuit-breaker co-ordination n Cascading
n Discrimination
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EC 60947-2
Specific points (appendix B) Residual current device Standard IEC 60947-2 appendix B defines n The characteristics of the residual current devices n The tests and verifications that must be performed on a residual current device o in order to guarantee the safety of the residual current function o in order to guarantee the quality of the residual current function
(malfunctioning)
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EC 60947-2
Specific points (appendix B) Residual current device Tests and verifications n Safety of the residual current function o after breaking at Icu and Ics, no deterioration of the earth leakage
protection units, o correct operation of the function: 14h30
duration (h)
- in harsh environmental conditions (damp heat 28-day cycle)
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EC 60947-2
Specific points (appendix B) Residual current device Tests and verifications n Quality of the residual current function o no nuisance tripping in the event of:
-
single-phase overcurrent (standardized tests) current waves generated by impulse voltage network capacitance load in event of an insulation fault with a DC component (class A),
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Specific points (appendix F) Circuit-breaker with electronic trip unit Standard IEC 60947-2 appendices F defines n The additional specifications for circuit-breakers with electronic trip unit n The tests required to guarantee their correct operation in restrictive industrial environments o EMC tests: immunity to disturbances, o EMC tests: verification of radiated emission level, o (very harsh) environmental tests, dry and damp heat, temperature variations After each test, verification of proper trip unit operation
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Specific points (appendix H) Circuit-breaker suitable for IT Standard IEC 60947-2 n Defines this breaking type (with a single pole at phase-to-phase voltage) n Stipulates a specific test o the devices not suitable for use with the IT system are marked with the symbol IT E55252
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EC 60947-2
Tests Standard IEC 60947-2 makes provision for complete device testing Cumulative tests grouped into sequences n One sample undergoes all the sequence tests 5 Test Sequences + 1 Combined test sequence n All the functions and characteristics are tested Specific tests n Circuit-breaker suitable for isolation n Residual current device, n Circuit-breaker with electronic trip unit, EMC Tests n etc.
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EC 60947-2
Tests Test sequences Category A Sequence 1 General operating characteristics Sequence 2 Service breaking capacity Ics Sequence 3 Ultimate breaking capacity Icu Sequence 4 Rated short time withstand current Icw Combined test sequence Example
Category B Icw < Ics
Icw = Ics
Icw = Ics = Icu
n
n
n
n
n
n
n
n
n
n
n NS100 to NS630 C801 to C1251 CM1251 + Multi 9 Masterpact H2-L1 to 3200
n Masterpact N1-H1
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EC 60947-2
Test sequences Example n Sequence 1 and 2 Test sequences
Sequence 1 General operating characteristics
Circuit-breaker type Cat. A Cat. B Icw Icw < Ics = Ics
n
Tests to be performed in turn on the same circuit-breaker
Additional tests for circuit-breakers declared suitable for isolation
1. Verification of tripping thresholds 2. Dielectric properties 2.1 If an Uimp is declared by the Manufacturer: Uimp Test phase-to phase, phase-to-earth 2.2 If no Uimp is declared Dielectric test 50 Hz at 2Ui + 1000 3. Mechanical durability 4. Electrical durability 5. Operation in overload at 6 In 6. Dielectric withstand at 2 Ue (min. 1000 V)
1. Ditto 2. Dielectric properties Uimp withstand compulsory: ditto opposite plus between Inlet and Outlet: Uimp + 25 % and leakage current test
7. Temperature rise at In 8. Verification of non-drift of overload trip units 1. Three successive current breakings Ics as per cycle O - 3 mm - CO - 3 mm - CO 2. Verification of suitability for operation, achievement of 5 % of electrical durability 3. Dielectric withstand at 2 Ue (50 Hz-1 mm)
7. Ditto 8. Ditto
4. Temperature rise at In 5. Verification of non-drift of overload trip units
4. Ditto 5. Ditto
Icw = Ics = Icu
(< 0.5 mA per pole at 110 % Ue)
3. Ditto 4. Ditto 5. Ditto 6. Ditto + leakage current test (< 2 mA per pole at 110 % Ue)
Sequence 2 Service breaking capacity Ics
n
1. Ditto 2. Ditto
3. Ditto + leakage test current (≤2 mA per pole at 110 % Ue)
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Tests n Tripping curves o all the important points on the tripping curve are tested o essential features are tested in real and the hardest conditions
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EC 60947-2
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EC 60947-2
Tests Icu In «sequence 3» of standardized tests O - t - CO test Verifications n Dielectric at 2 Ue (minimum 1000 V) for 1 minute, NB: for circuit-breaker suitable for isolation test of leakage I = < 6 mA at 110 % Ue
n Verification of overload trip units at 2 Ir
Standard IEC 60947-2 clarifies the definition of circuit-breaker breaking capacity The circuit-breaker must not be «dangerous » after 2 breakings at Icu
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EC 60947-2
Tests Ics In « sequence 2 » of standardized tests O - t - CO - t - CO test Verifications n Dielectric at 2 Ue (minimum 1000 V) for 1 minute, NB: for circuit-breaker suitable for isolation test of leakage I ≤2 mA at 110 % Ue n Of suitability to break its nominal current by achieving 5% of electrical durability n Of temperature rise at In, n Verification of overload trip units at Ir The circuit-breaker must be suitable for operation after a short circuit at Ics. This performance is guaranteed 3 times. The Ics performance represents a « practical » breaking capacity.
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EC 60947-2
Tests Icw In « sequence 4 » of standardized tests Category B circuit-breaker Verifications n Device withstand at Icw and ∆t indicated by the manufacturer n Of temperature rise at In, after O - t - CO cycle at Icw at maximum voltage n Dielectric at 2 U 1(minimum 1000 V) for 1 minute, n Overload trip units at 2 Ir
The circuit-breaker must be suitable for operation after a short-circuit at Icw
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EC 60947-2
Conclusion Standard IEC 60947-2
A standard that adheres to reality Simple, clear choice of circuit-breakers n In and Icu are sufficient to determine the circuit-breaker, New recognized, defined and tested characteristics / functions n Suitability for isolation, n Residual current device, n Circuit-breakers with electronic trip unit Tests representative of the real stresses exerted on a circuit-breaker n Ics, etc. n Cumulative tests in sequences, n Tests of all the design characteristics
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Conclusion
EC 60947-2
Standard IEC 60947-2
A standard that adheres to reality Examples 1250 kVA Sub-distribution board 18 kA MSB
160 A 28 kA
o probable Isc very close to
prospective Isc: Ics = 100 % Icu NS160N is optimized
8.5 kA
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Isc = 29 kA
o probable Isc less than
prospective Isc: Ics = 50 % Icu C60L is optimized
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Conclusion E55256
EC 60947-2
A circuit-breaker certified according to Standard IEC 60947-2 guarantees a quality device with durable performance of all its safety functions.
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