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TRANSCRIPT
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International standard
IEC 60947-2Low voltage switchgear
Part 2: Circuit-breakers
DBTP83-En-06/00
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Standard IEC 60947-2 Contents
I. General 3
2. Definitions 8
3. Circuit-breaker characteristics 10
4. Constructional requirements 14
5. Specific points (appendices) 21
6. Tests 27
7. Conclusion 34
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Standard IEC 60947-2
Standard IEC 60947-2
Came into f orce in 1999
Takes into account the circuit-br eaker main technological upgr ades
Standard IEC 60947-2
Is internationally r ecognized and approved
and is applied in the majority of countries (> 100)
General
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IEC
IEC
UL
CSAIEC
JIS/IEC
IEC
IEC
IEC
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Standard IEC 60947-2 General
The scope« 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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Standard IEC 60947-2 General
The scopeStandard IEC 60947-2 contains additional specifications for:
Circuit-br eaker s suitable f or isolation
Residual curr ent devices (appendix B)
Circuit-br eaker s with electronic protection (appendices J and F)
Circuit-br eaker s f or IT systems (appendix H)
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Standard IEC 60947-2 General
Standard IEC 60947-2 defines
The circuit-br eaker classification
accor ding to utilization category A or B
accor ding to design type
air circuit-br eaker, moulded case circuit-br eaker
The circuit-br eaker mechanical and electr ical data:
size, tr ip unit, etc.
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Standard IEC 60947-2 Definitions
Circuit-breaker classification
Utilization category A Utilization category B
Circuit-br eaker not specifically intended Circuit-br eaker specifically intended
f or discr imination f or discr imination:
Without an intentional short-time delay With intentional short-time delay
(adjustable)
Without short time withstand curr ent With short time withstand curr ent
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Standard IEC 60947-2
Extract from appendix K of standard IEC 60947-2
Characteristics Ue Rated oper ational voltage
voltage Ui Rated insulation voltage
Uimp Rated impulse withstand voltage
curr ent In Rated curr ent
Ith Conventional f r ee-air ther mal curr entIthe Conventional enclosed ther mal curr ent
Icm Rated short-circuit making capacity
short-circuit Icu Rated ultimate short-circuit br eaking capacity
Ics Rated service short-circuit br eaking capacity
Icw Rated short-time withstand curr ent
Ir Adjustable overload setting curr ent
1.05 x Ir Conventional non-tr ipping curr enttr ip unit 1.30 x Ir Conventional tr ipping curr ent
Isd Short time delay tr ipping setting curr ent
Ii Instantaneous tr ipping setting curr ent
Definitions
Terminology / Vocabulary
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Standard IEC 60947-2 Circuit-breaker characteristics
Overload withstandIn (in A rms) = rated current
Maximum uninterrupted curr ent
withstood at ambient
temper atur e, given without
abnor mal temper atur e r ise
Ir (in A rms) = adjustable
overload setting current
Ir depends on In
Ir char acter izes the
overload protection
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Standard IEC 60947-2 Circuit-breaker characteristics
Short-circuit withstandIcu (kA rms) = rated ultimate
short-circuit breaking capacity
This per f or mance expr esses
the maximum value of the
short-circuit curr ent that can
be broken by the circuit-br eaker
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Standard IEC 60947-2 Circuit-breaker characteristics
Short-circuit withstand
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Standard IEC 60947-2 introduces a
new important performance
Ics (as a % of Icu) = rated service
short-circuit breaking capacity
This per f or mance expr esses
the suitability of a circuit-br eaker toensur e f ully nor mal service af ter
br eaking this curr ent 3 times
Nor mal r atio between Ics and Icu
Utilization category A Utilization category B% of Icu % of Icu
2550 50
75 75
100 100
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Standard IEC 60947-2Safety in use: breaking capacity tests simulate
those encountered in "real life"
Prospective short circuit curr ent (Isc) & ultimate short circuit br eaking capacity(Icu)
when designing an installation, the wor st case of short circuit curr ent is calculated : we call this
the "prospective short circuit curr ent".
prospective Isc: theor etical thr ee phase short circuit at the ter minals of the
circuit br eaker
"bolted" short circuit (without arc and impedance)
the circuit br eaker must be capable of interrupting this short circuit (a fault very unlikely to
occur except dur ing commissioning).
ultimate short circuit breaking capacity (Icu):
maximum short circuit curr ent that the br eaker can interrupt.
is the only short circuit breaking capacity that needs tobe considered when selecting a breaker.
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Standard IEC 60947-2
Safety in use: breaking capacity tests
simulate those encountered in "real life"
prospective short circuit level (Isc) & service br eaking capacity (Ics)
in pr actice, short circuit curr ents ar e much lower than the calculated prospective short
circuit level because they ar e strongly limited by :
the impedance of cables and connections
the electr ic arc (within the br eaker) its type : phase-neutr al or between two phase.
r educed short circuits ar e mor e probable as they ar e gener ally some distance away
f rom the tr ansf or mer .
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Standard IEC 60947-2 Circuit-breaker characteristics
Short-circuit withstandStandard IEC 60947-2 introduces anew performance for category B circuit-breakers
Icw (in kA rms) = rated short-timewithstand current
Icw is the maximum short-circuitcurr ent that a circuit-br eaker can
withstand f or a short dur ation(t without deter ior ation of these char acter istics
ICW must be at least equal to12 In or 5 kA f or In e 2500 A30 kA f or I
n
> 2500 A
The standar dized delay time (tis: 0.05 - 0.1 - 0.25 - 0.5 -or 1s
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Standard IEC 60947-2 Constructional requirements
Isolation co-ordinationThe circuit-breaker, as a safety device, must be able to withstand
Networ k overvoltages
this suitability is char acter ized by the withstand to the conventional
dielectr ic test at 2 Ui + 1000 - 1 min at power f r equency
Impulse voltages ( «lightning stroke» simulation)
this suitability is char acter ized by the withstand to the1.2/ 50 Qs impulse voltage test of value Uimp
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Standard IEC 60947-2 Constructional requirements
Isolation co-ordinationUimp (kV peak) = rated impulse withstand voltage
Characterization of Uimp
Depends on the LV networ k voltage
Depends on the position of the circuit-br eaker in the LV networ k
Depends on altitude: Uimp must be valid up to 2000 m
tests carr ied out at +23 % of value
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Standard IEC 60947-2
Characterization of Uimp
Nominal Applications
installation voltage
at the or igin of the on the distr ibution and at loadinstallation/MSB final circuits level
230 /400 V 6 4 2.5
400 /690 V 8 6 4
Constructional requirements
Isolation co-ordination
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Standard IEC 60947-2
Constructional requirements
Isolation co-ordination E 5 5 2 4 4
Industrial circuit-breaker Uimp = 8 kV
Tests to be consider ed
Uimp + 23 % = 9.8 kV
standar d industr ial circuit-br eaker s and those suitable f or isolation
Application of Impulse voltage value
impulse voltage Breakers Disconnector Breakers
Phase-to-phase 9.8 kV 9.8 kV
Up-to-downstr eam 12.3 kV (*)
contacts open
Phase-to-earth 9.8 kV 9.8 kV
(*) 14.7 kV f or f ront face class II circuit-br eaker as per IEC 61 140
Test between upstr eam
and downstr eam
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Standard IEC 60947-2 Constructional requirementsCircuit-breaker suitable for isolation
Test of isolation suitability
3 tests designed to ensur e user s that a device
«suitable f or isolation» is not dangerous
in open position...
- even af ter having eliminated a short-circuit up to Icu
- even in the event of overvoltage on the networ k ...
or in closed position
cannot be declar ed «open» and/or « padlockable »
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Standard IEC 60947-2 Constructional requirementsCircuit-breaker suitable for isolation
Leakage current measurement test
at 110 % of maximum utilization voltage Ue
New device, leakage curr ent < 0.5 mA per pole,
Af ter br eaking at Ics, leakage curr ent < 2 mA per pole,
Af ter dur ability tests, leakage curr ent < 2 mA per pole,
Af ter br eaking at Icu, leakage curr ent < 6 mA per pole
Impulse voltage withstand
Uimp = 12 kV (instead of 9.8 kV) between the inlet and the outlet of the
open device
(*) 14.7 kV f or f ront face class II circuit-br eaker as per IEC 61 140
Mechanical ruggedness test
Circuit-br eaker 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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Class ll
enclosur e
Class ll
f ront face
Front face class ll
Mechanical ruggedness
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Standard IEC 60947-2 Constructional requirementsCircuit-breaker /isolator
Marking
A circuit-br eaker that is «suitable for isolation» will display the circuit-
br eaker/isolator symbol on its f ront face
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Standard IEC 60947-2 Specific points (appendix A)
Cascading Discr imination
Standard IEC 60947-2 recognizes and defines circuit-breaker
co-ordination
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Standard IEC 60947-2 Specific points (appendix B)Residual current device
Standard IEC 60947-2 appendix B defines
The char acter istics of the r esidual curr ent devices
The tests and ver ifications that must be per f or med on a r esidual curr ent
device
in or der to guar antee the safety of the r esidual curr ent f unction
in or der to guar antee the quality of the r esidual curr ent f unction
(malf unctioning)
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Standard IEC 60947-2 Specific points (appendix B)Residual current device
Tests and verifications
Quality of the r esidual curr ent f unction
no nuisance tr ipping in the event of:
- single-phase overcurr ent (standar dized tests)
- curr ent waves gener ated by impulse voltage
- networ k capacitance load
- in event of an insulation fault with a DC component
(class A),
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Class A cycle
I fault
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Standard IEC 60947-2 Specific points (appendix B)Residual current device
Tests and verifications
Safety of the r esidual curr ent f unction
af ter br eaking at Icu and Ics, no deter ior ation of the earth leakage
protection units,
corr ect oper ation of the f unction:- in har sh environmental conditions
(damp heat 28-day cycle)0 12 14h30
Hygro (%)
100
90
55
25
t
(°C)
dur ation
(h)
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Standard IEC 60947-2 Specific points (appendix F)Circuit-breaker with electronic trip unit
Standard IEC 60947-2 appendices F defines
The additional specificationsf or circuit-br eaker s withelectronic tr ip unit
The tests r equir ed to guar anteetheir corr ect oper ation in
r estr ictive industr ialenvironments
EMC tests: immunity todisturbances,
EMC tests: ver ification of r adiated emission level,
(very har sh) environmental
tests, dry and damp heat,temper atur e var iationsAfter each test,verification of proper trip unit operation
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Standard IEC 60947-2 Specific points (appendix H)
Circuit-breaker suitable for IT
Standard IEC 60947-2
Defines this br eaking type
(with a single pole at phase-to-phase voltage)
Stipulates a specific test
the devices not suitable f or use with the IT system ar e mar kedwith the symbol IT
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Standard IEC 60947-2 Tests
Standard IEC 60947-2 makes provision for complete device testing
Cumulative tests grouped into sequences
One sample undergoes all the sequence tests
5 Test Sequences + 1 Combined test sequence
All the f unctions and char acter istics ar e tested
Specific tests
Circuit-br eaker suitable f or isolation
Residual curr ent device,
Circuit-br eaker with electronic tr ip unit,
EMC Tests
etc.
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Standard IEC 60947-2
Test sequencesCategoryA Category B
Ics < Icu Icw = Ics = Icu
Sequence 1Gener al oper ating
char acter istics
Sequence 2Service br eaking
capacity Ics
Sequence3Ultimate br eaking
capacity Icu
Sequence 4Rated short time
withstand curr ent Icw
Combinedtest sequence
Example NS630b to 1000 L NS630b to 1600 N-HNS100 to NS630 NS1600b to 3200 N-H Masterpact + Multi 9 Masterpact H2-H3-L1 N1-H1
Tests
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Standard IEC 60947-2
Example Sequence 1 and 2Test Circuit-breaker type Tests to be performed in turn Additional tests for sequences Cat. A Cat. B on the same circuit-breaker circuit-breakers declared
Icw Icw Icw suitable for isolation< Ics = Ics = Ics
= Icu
Sequence 1 1. Ver ification of tr ipping thr esholds 1. DittoGener al 2. Dielectr ic properties 2. Dielectr ic propertiesoper ating 2.1 If an Uimp is declar ed by the Uimp withstand compulsory:
char acter istics Manufactur er : Uimp Test phase-to ditto opposite plus between phase, phase-to-earth Inlet and Outlet: Uimp + 25 %
2.2 If no Uimp is declar ed and leakage curr ent testDielectr ic test 50 Hz at 2Ui + 1000 (< 0.5 mA per pole at 110 % Ue)
3. Mechanical dur ability 3. Ditto4. Electr ical dur ability 4. Ditto5. Oper ation in overload at 6 In 5. Ditto6. Dielectr ic withstand at 2 Ue (min. 1000 V) 6. Ditto + leakage curr ent test
(< 2 mA per pole at 110 % Ue)7. Temper atur e r ise at In 7. Ditto8. Ver ification of non-dr if t of 8. Ditto
overload tr ip units
Sequence 2 1. Thr ee successive curr ent br eakings Ics 1. DittoService as per cycle O - 3 mm - CO - 3 mm - CO
br eaking 2. Ver ification of suitability f or 2. Dittocapacity Ics oper ation, achievement of 5 %
of electr ical dur ability3. Dielectr ic withstand at 2 Ue (50 Hz-1 mm) 3. Ditto + leakage test curr ent
(e 2 mA per pole at 110 % Ue)4. Temper atur e r ise at In 4. Ditto5. Ver ification of non-dr if t of 5. Ditto
overload tr ip units
Test sequences
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Standard IEC 60947-2 Tests
Tripping curves
all the important points
on the tr ipping curve
ar e tested
essential featur es ar e tested in r eal
and the har dest conditions
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Standard IEC 60947-2
In «sequence 3» of standardized tests
O - t - CO test
Verifications
Dielectr ic at 2 Ui (minimum 1000 V) f or 1 minute,
NB: f or circuit-br eaker suitable f or isolation test of leakage I = < 6 mA at 110 % Ue
Ver ification of overload tr ip 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
Tests Icu
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Standard IEC 60947-2 Tests Ics
In « sequence 2 » of standardized tests
O - t - CO - t - CO test
Verifications
Dielectr ic at 2 Ui (minimum 1000 V) f or 1 minute,
NB: f or circuit-br eaker suitable f or isolation test of leakage I e 2 mA at 110 % Ue
Of suitability to br eak its nominal curr ent by achieving 5% of electr ical
dur ability
Of temper atur e r ise at In,
Ver ification of overload tr ip 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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Standard IEC 60947-2
In « sequence 4 » of standardized tests
Category B circuit-breaker
Verifications
Device withstand at Icw and (t indicated by the manufactur er
Of temper atur e r ise at In, af ter O - t - CO cycleat Icw at maximum voltage
Dielectr ic at 2 U 1(minimum 1000 V) f or 1 minute,
Overload tr ip units at 2 Ir
The circuit-breaker must be suitable for operation after a short-circuit at Icw
Tests Icw
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Standard IEC 60947-2 Conclusion
Standard IEC 60947-2
A standard that adheres to reality
Simple, clear choice of circuit-breakers
In and Icu ar e sufficient to deter mine the circuit-br eaker,
New recognized, defined and tested characteristics / functions
Suitability f or isolation,
Residual curr ent device,
Circuit-br eaker s with electronic tr ip unit
Tests representative of the real stresses exerted on a circuit-breaker
Ics, etc.
Cumulative tests in sequences, Tests of all the design char acter istics
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Standard IEC 60947-2
Standard IEC 60947-2
A standard that adheres to reality
Examples
probable Isc very close to probable Isc less than
prospective Isc: Ics = 100 % Icu prospective Isc: Ics = 50 % Icu
NS160N is optimized C60L is optimized
Conclusion
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1250 kVA
Isc = 29 kA
28 kA
160 A
MSB
Sub-distributionboard
18 kA
8.5 kA
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Standard IEC 60947-2 Conclusion
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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