Noah wrote:

I am using PTW32 too, can anyone explain why I have to use comprehensive SC for Arc fault calculation? What's the big difference if I want to use A_Fault? Thanks!

Noah,

I do not know if someone has answered your question or not but I believe the difference is in the fault current magnitude. The fault current magnitude obtained using comprehensive method (which is strictly theoretical) is the same as the ANSI fault during the first half of cycle with small variation in X/R ratio. After that the ANSI multipliers for sources and motor contributions kick in...which eventually reduces the magnitude.

The arc-flash result should remain the same since PTW uses initial symmetrical RMS current (at 1/2 cycle) for its calculations.

Aleen

Burns & McDonnell