8.4.3 Magnetizing inrush during fault removal
When a fault external to, but near, the transformer is removed by the appropriate circuit breaker,
the conditions inside the transformer core are quite similar to those during magnetization of the
transformer.1,3 As the voltage applied to the transformer windings jumps from a low prefault value
to the normal (or larger) postfault value, the flux linkages in the transformer core are once again
forced to change from a low prefault value to a value close to normal. Depending upon the instant
at which the fault is removed, the transition may force a DC offset on the flux linkages, and primary
current waveforms similar to those encountered during energization would result. It should be noted
that as there is no remnant flux in the core during this process; the inrush is in general smaller than
that during the transformer energization.