Short-Circuit Current Vs. Short-Circuit Withstand Current 2

[Ohal]

Can anyone please explain the difference between the terms "Short-Circuit Current", "Short-Circuit Withstand Current", and "Peak withstand current"?
Thank you.

 

[burnt2x]

Google it.

 

[jefferslot]

In simple terms
and in terms of switchgear rating, short circuit current is the RMS sustained maximum short circuit current (eg 25KA).
Short circuit withstand is the ability of the switchgear to sustain or carry a short circuit condition and is time rated (3 seconds or 1 second eg 25KA) but will have an asymmetrical component at the commencement of the test (this is an off-set current waveform which you refer to as peak withstand current), the effect on the switchgear is dynamic. the maximum peak withstand at the commencement of the test is a multiplication of the RMS which at 50Hz is 2.5 and at 60Hz is 2.6.

Switchgear which is rated for 12KV 25KA (3seconds) 50Hz for example, will have the ability to make onto a peak of 62.5A, and thereafter sustain the RMS of 25KA for 3 seconds. the indivudual circuit breaker would also be capable of making onto the fault of peak value 62.5KA and be capable of breaking 25KA fault current.

The breaking condition is a little more complex than "just 25KA" because a DC component is introduced which is very onerous for the circuit breaker to consider, but i hope this gives you a start

Jeff

 

[Ohal]

Jeff

Thank you very much for the assistance. Much appreciated.