Fault Calculation Basis

The fault calculations are based on IEEE Std 242-1975 Recommended Practice for Protection and Coordination of Industrial and Commercial Power Systems.

The fault that is calculated is the three-phase line-to-line fault.

Fault = Voltage / sqrt(Resistance2 + Reactance2)

The feeder impedance values are based upon NEC Table 9. These values can be modified by the user using the Wire Ampacities command.

The transformer impedance values are for dry-type indoor transformers. These values can be modified by the user using the Panel Edit command or Family Edit command.


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