There is an interesting glitch with the IEEE 1584 equation for arcing short circuit current at or above 1 kV.

The equation for arcing current at higher voltages > 1 kV:

Log Ia = 0.00402 + [0.983 (Log Ibf)]

Ia = 10^(Log Ia)

Where:

Ibf = 3 phase bolted short circuit current in kA

Ia = 3 phase arcing short circuit current

IEEE range of validity 700A to 106 kA

Here’s the glitch. If the bolted current is 1,000 Amps i.e. 1 kA:

Log Ia = 0.00402 + 0.983 X Log (1)

Log of 1 = 0

Therefore:

Log Ia = 0.00402 + 0.983 X 0

Log Ia = 0.00402 + 0

Log Ia = 0.00402

Ia = 10^(Log Ia)

Ia = 10^0.00402 = 1.0093 kA

So….. Ibolted = 1,000 Amps and Iarcing =1,009.3 Amps

Except it is physically impossible to have Iarcing greater than Ibolted.

Oops!