MV design guide - Schneider Electric

Standards
IEC- ANSI comparison
Derating
According to IEC
c Refer to "Switchgear definition/Derating" chapter.
According to ANSI
c 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 level
and 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).
Altitude
ACF for:
(ft) (m) voltage continous current
3 300 1 000 1.00 1.00
5 000 1 500 0.95 0.99
10 000 3 000 0.8 0.96
N.B.: "sealed system" type circuit breakers,
it is not necessairy to apply the voltage ACF on the maximum rated voltage
Electrical endurance
Merlin Gerin circuit breakers can withstand Isc at least 15 times.
IEC and ANSI standards impose values well below this because they take
account 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 IEC
c The electrical endurance is equal to 3 times Isc.
According to ANSI
c The electrical endurance is equal to 4 times K.S.Isc.
Isc : symmetrical breaking capacity at maximum voltage
S : asymmetrical factor
K : voltage range factor
Mechanical endurance
According to IEC
c Mechanical endurance is of 2 000 switching cycles.
According to ANSI
c Mechanical endurance is of between 1 500 and 10 000 switching cycles
according to the voltage and the breaking capacity.
Construction
According to IEC
c The IEC does not impose any particular constraints, however,
the manufacturer has responsibility of determining what is required in
terms of materials (thicknesses, etc) to meet performance requirements in
terms of strength.
According to ANSI
c ANSI imposes a thickness of 3 mm for sheet metal.
78 Merlin Gerin MV Design Guide Schneider Electric