Transformer Grounding Resistor Extended Rating

[kingi]

When a 400 amp 10 second grounding resistor is subjected to fault currents above 400 amp, how can I calculate the time this resistor can stand at the higher fault currents

 

[davidbeach]

Typically I²T, but a properly sized 400A grounding resistor will not be subjected to more than 400A without a significant overvoltage somewhere.