IEC - ANSI comparison - Schneider Electric

StandardsThe standards mentionedin this documentWhere can you orderIEC publications?Central Offices of the InternationalElectrotechnical Commission1, rue de Varembé Geneva - Switzerland.The documentation department (Factory A2)at Merlin Gerin can provide you withinformation on the standards.c International Electrotechnical Vocabulary IEC 60 050c High voltage alternating currentcircuit breakers IEC 60 056c Current transformers IEC 60 185c Voltage transformers IEC 60 186c Alternating current disconnectorsand earthing disconnectors IEC 60 129c High voltage switches IEC 60 265c Metal-enclosed switchgear for alternatingcurrent at rated voltage of over 1 kV andless than or equal to 72.5 kV IEC 60 298c High-voltage alternating currentcombined fuse-switches and combinedfuse-circuit breakers IEC 60 420c High-voltage alternatingcurrent contactors IEC 60 470c Specifications common to highvoltageswitchgear standards IEC 60 694c Calculation rulesin industrial installations IEC 60 909c Derating ANSI C37 04Schneider ElectricMerlin Gerin MV Design Guide71

StandardsIEC - ANSI comparisonThe following comparisonis based ondifferent circuit breakercharacteristics.Overview of the main differencesTheme ANSI IECasymmetrical breaking 50% 30%capacity on faults with current without deratingacross the terminals deratinginsulation level:imposes chopped wavesimpulse wavefor outdoor equipment115% Uw/3 s129% Uw/2 sshort-time withstand 2.7 Isc 2.5•Isc at 50 Hzcurrent peak2.6•Isc at 60 Hzvalue2.7•Isc for special casesTransient Recovery around twicevoltage (1)as severeelectrical endurance 4 times K.S.Isc 3 times Iscmechanical endurance 1 500 to 10 000 2 000according to Ua and Iscmotor overvoltages no text standard test circuit(1) the ANSI peak voltage is 10% greater than the voltage defined by the IEC.The E2/t2 slope is 50% greater than the Uc/t3 slope.However, the largest part of the graph is the initial part where the SF6 reconstitutes itself.The two standards easily allow the SF6 to reconstitute itself.Rated voltagesAccording to IECc Standardised values for Ur (kV): 3.6 - 7.2 - 12 - 17.5 - 24 - 36 kVAccording to ANSIc The ANSI standard defines a class and a voltage range factor Kwhich defines a range of rated voltages at constant power.Standardised values for Ur (kV)class (kV) Umax (kV) Umin (kV) KIndoor equipment 4.16 4.76 3.85 1.247.2 8.25 6.6 1.2513.8 15 11.5 1.338 38 23 1.65Outdoor equipment 15.5 125 138 1100905010Upeak (%)1.2 µs50 µsStandardised wave 1.2/50 µst (µs)Rated installation levelAccording to IECRated Rated lightning Rated power frequencyvoltage withstand voltage withstand voltage(kV) (kV) 50 Hz 1 mm (kV)7.2 60 2012 75 2817.5 95 3824 125 5036 170 7072 Merlin Gerin MV Design Guide Schneider Electric

StandardsIEC - ANSI comparison10090705010Upeak (%)tcOnde coupée suivant ANSIpour le matériel d'extérieurt (µs)According to ANSIRated Rated lightning Rated power frequencyvoltage withstand voltage withstand voltage(kV) (kV) 50 Hz 1 mm (kV)Indoor equipment4.16 60 197.2 95 3613.8 95 3638 150 80Outdoor equipment15.5 110 5025.8 125 6015038 150 80200N.B.c BIL: Basic Insulation LevelThe outdoor equipment is tested with chopped waves.c The impulse withstand is equal to:1.29 BIL for a duration of tc = 2 µs1.15 BIL for a duration tc = 3 µsRated normal currentAccording to IECc Values of rated current: 400 - 630 - 1250 - 1600 - 2500 - 3150 AAccording to ANSIc Values of rated current: 1200 - 2000 - 3000 AShort-time withstand currentAccording to IECc Values of short-circuit rated breaking capacity:6.3 - 8 - 10 - 12.5 - 16 - 20 - 25 - 31.5 - 40 - 50 - 63 kAAccording to ANSIc Values of short-circuit rated breaking capacity:v indoor equipment: 12.5 - 20 - 25 - 31.5 - 40 kAv outdoor equipment:Class (MVA)Breaking capacity (kA)I at UmaxKI at Umin250 29 36350 41 49500 18 23750 28 361000 37 461500 21 352750 40 40Schneider ElectricMerlin Gerin MV Design Guide73

StandardsIEC - ANSI comparisonPeak value of short-time currentand closing capacityAccording to IECc The peak value of short-time withstand current is equal to:v 2.5•Isc at 50 Hzv 2.6•Isc at 60 Hzv 2.7•Isc for special cases.According to ANSIc The peak value of short-time withstand current is equal to:v 2.7 K Isc at peak valuev 1.6 K Isc at rms. value.(K : voltage factor)Rated short-circuit durationAccording to IECc The rated short-circuit duration is equal to 1 or 3 seconds.According to ANSIc The rated short-circuit duration is equal to 3 seconds.Rated supply voltagefor closing and openingdevices and auxiliary circuitsAccording to IECc Supply voltage values for auxiliary circuits:v for direct current (dc): 24 - 48 - 60 - 110 or 125 - 220 or 250 voltsv for alternating current (ac): 120 - 220 - 230 - 240 volts.c Operating voltages must fall within the following ranges:v Motor and closing release units:-15% to +10% of Ur in dc et acv opening release units:-15% to +10% of Ur in ac; -30% to +10% of Ur in dcv undervoltage opening release unitsthe release unit givesthe command andforbids closing0 % 35 % 70 % 100 %According to ANSIc Supply voltage values for auxiliary circuits:v for direct current (dc): 24 - 48 - 125 - 250 volts.v for alternating (ac): 120 - 240 voltsthe release unitmust not havean action(at 85%, the release unit must enablethe device to close)U74 Merlin Gerin MV Design Guide Schneider Electric

StandardsIEC - ANSI comparisonc Operating voltage must fall within the following ranges:VoltageVoltage range (V)Motor and closing release units48 Vsc 36 to 56125 Vsc 90 to 140250 Vsc 180 to 280120 Vac 104 to 127240 Vac 208 to 254Opening release units24 Vsc 14 to 2848 Vsc 28 to 56125 Vsc 70 to 140250 Vsc 140 to 220120 Vac 104 to 127240 Vac 208 to 254Rated frequencyAccording to IECc Rated frequency: 50 Hz.According to ANSIc Rated frequency: 60 Hz.Short-circuit breaking capacityat the rated operating sequencec ANSI specifies 50% asymmetry and IEC 30%. In 95% of applications,30% is sufficient. When 30% is too low, there are specific cases (proximityof generators) for which the asymmetry may be greater than 50%.c For both standard systems, the designer has to check the circuit breakerbreaking capacity. The difference is not important because without takingaccount of the asymmetry factor "S", it is equal to 10%.ANSI: Iasym = Isym (1 + 2 A 2 ) = 1.22 Isym (A = 50%)IEC: Iasym = Isym (1 + 2 A 2 ) = 1.08 Isym (A = 30%)According to IECc Short-circuit breaking tests must meet the following 5 test sequences:Sequence n° % Isym % aperiodic component1 10 ≤ 202 20 ≤ 203 60 ≤ 204 100 ≤ 205* 100 30* for circuit breakers opening at least 80 msSchneider ElectricMerlin Gerin MV Design Guide75

StandardsIEC - ANSI comparisonAccording to ANSIc The circuit breaker must be able to break:v the rated short circuit current at the rated maximum voltagev K times the rated short-circuit current (maxi symmetrical interruptingcapability with K: voltage range factor) at the operating voltage (maximumvoltage/K)v between the two currents obtained by the equation:maxi symetrical currentrated short-circuit currentrated maxi voltage= = Krated voltageWe therefore have a constant breaking power (in MVA) over a givenvoltage range. Moreover, the asymmetrical current will be a function of thefollowing table taking S = 1.1 for Merlin Gerin circuit breakers.1.81.71.61.51.41.31.21.11ratio SAsymmetrical interrupting capability = S x symetrical interrupting capability.Both at specified operating voltageSymetrical interrupting capability atspecified operating voltage = 1.00 0.5 1 2 3 40 0.006 0.017 0.033 0.050 0.067cyclessecondsExample:c Isc = 40 kAc % asymmetry = 50%c Iasym = 1.1 • 40 = 44 kA44 44c Isym = = = 36 kA1 + 2(50%) 2 1,22Sequence 6 will therefore be tested at36 kA + 50% asymmetry,this being 44 kA of total current.c Rated short-circuit breaking capacity (kA)Sequence n° current broken % aperiodic component1 10 50 - 1002 30 < 203 60 50 - 1004 100 < 205 KI to V/K < 206 SI to V 50 - 1007 KSI to V/K 50 - 1008 electrical endurance9/10 reclosing cycle at ASI and AKSI11 C - 2 s - O at KI12 rated Isc duration = KI for 3 s13/14 single phase testing at KI and KSI (0.58 V)Short-circuit breaking testing must comply with the14 test sequences above, with:I : symmetrical breaking capacity at maximum voltageR : reclosing cycle coefficient(Reclosing factor)K : voltage range factor:K = VmaxVminIasymS : asymmetrical factor: = 1.1Isymfor Merlin Gerin circuit breakersV : maximum rated voltage76 Merlin Gerin MV Design Guide Schneider Electric

StandardsIEC - ANSI comparisonCoordination of rated valuesAccording to IECRated Rated short-circuit Rated operating currentvoltage breaking currentUr (kV) Isc (kA) Ir (A)3.6 10 40016 630 125025 1250 1600 250040 1250 1600 2500 31507.2 8 40012.5 400 630 125016 630 1250 160025 630 1250 1600 250040 1250 1600 2500 315012 8 40012.5 400 630 125016 630 1250 160025 630 1250 1600 250040 1250 1600 2500 315050 1250 1600 2500 315017.5 8 400 630 125012.5 630 125016 630 125025 125040 1250 1600 2500 315024 8 400 630 125012.5 630 125016 630 125025 1250 1600 250040 1250 1600 2500 315036 8 63012.5 630 125016 630 1250 160025 1250 1600 250040 1250 1600 2500 3150According to ANSIMaximum Rated Minimum Rated Ratedrated short-circuit rated short-circuit operatingvoltage breaking current voltage breaking current currentat Umaxat UminUmax (kV) Isc (kA) (kV) Isc (kA) Ir (A)4.76 18 3.5 24 120029 3.85 36 1200 200041 4 49 1200 30008.25 7 2.3 25 600 1200 200017 4.6 30 120033 6.6 41 1200 200015 9.3 6.6 21 12009.8 4 37 120018 11.5 23 1200 200019 6.6 43 1200 200028 11.5 36 1200 200037 11.5 48 1200 300015.5 8.9 5.8 24 60018 12 23 120035 12 45 120056 12 73 2000 3000 400025.8 5.4 12 12 60011 12 24 120038 22 23 36 1200 300036 24 57 1200Schneider ElectricMerlin Gerin MV Design Guide77

StandardsIEC- ANSI comparisonDeratingAccording to IECc Refer to "Switchgear definition/Derating" chapter.According to ANSIc The ANSI standard C37 04 gives for altitudes greater than 1 000 metres:v a correction factor for the applicable voltage on the rated insulation leveland on the rated maximum voltage,v a correction factor for the rated operating current.The table of correction factors according to altitude(Altitude Corrections Factors: ACF).AltitudeACF for:(ft) (m) voltage continous current3 300 1 000 1.00 1.005 000 1 500 0.95 0.9910 000 3 000 0.8 0.96N.B.: "sealed system" type circuit breakers,it is not necessairy to apply the voltage ACF on the maximum rated voltageElectrical enduranceMerlin Gerin circuit breakers can withstand Isc at least 15 times.IEC and ANSI standards impose values well below this because they takeaccount of oil breaking circuit breakers.These values are not very high and should the customer request it,we must provide those for the device being considered.According to IECc The electrical endurance is equal to 3 times Isc.According to ANSIc The electrical endurance is equal to 4 times K.S.Isc.Isc : symmetrical breaking capacity at maximum voltageS : asymmetrical factorK : voltage range factorMechanical enduranceAccording to IECc Mechanical endurance is of 2 000 switching cycles.According to ANSIc Mechanical endurance is of between 1 500 and 10 000 switching cyclesaccording to the voltage and the breaking capacity.ConstructionAccording to IECc The IEC does not impose any particular constraints, however,the manufacturer has responsibility of determining what is required interms of materials (thicknesses, etc) to meet performance requirements interms of strength.According to ANSIc ANSI imposes a thickness of 3 mm for sheet metal.78 Merlin Gerin MV Design Guide Schneider Electric

StandardsIEC - ANSI comparisonEquipment is designedto operate under thefollowing normalconditionsNormal operating conditionsTemperatureStandards 0°C Installationambient instantaneous indoor outdoorIEC minimal - 5°C - 25°Cmaximal + 40°C + 40°Cmaximum average 35°C 35°Cdaily valueANSI minimal - 30°Cmaximal + 40°CN.B.:For all equipment operating under conditions other than those described above, derating mustbe provided (see derating chapter).AltitudeAccording to IECc The altitude must not exceed 1 000 metres, otherwise the equipmentshould be derated.According to ANSIc The altitude must not exceed 3 300 feet (1 000 metres), otherwise theequipment should be derated.HumidityAccording to IECAverage relative humidityIndoor equipmentvalue over a period24 hours 95 %1 month 90 %According to ANSIc No specific constraints.Schneider ElectricMerlin Gerin MV Design Guide79