Create a single-line diagram and reduce the network to a single equivalent impedance ($Z_{eq}$) seen from the fault point.
For a 3-phase transformer:
“Just connect it to the main 11 kV bus,” said the project manager. “The breaker we have in stock is rated for 25 kA. That should be plenty.” short ckt current calculation
At its simplest, a short circuit happens when electricity finds a path with , causing the current to spike uncontrollably. 1. The Core Formula (Ohm’s Law) Create a single-line diagram and reduce the network
“Your full load current on the low side (400V) is about 3,600 amps. With 5% impedance (0.05 pu), your short-circuit current is 3,600 / 0.05 = (72 kA).” That should be plenty
Mike’s face went pale. “But our breaker is only rated for 25 kA.”
To find the maximum fault current on the secondary side of a transformer, follow these steps: