How to monitor ground fault in tertiary winding transformer Primary- Delta -6.6 KV 3 Ph, Secondary 1- Delta 2- Star 710 Volts 3 Phase 50 Hz Unearth used for 12 pulse VVFD. The Secondary voltage from transformer to Drive is in floating state.
Zero sequence voltage is about the only way to detect a ground on an "ungrounded" system. Not completely ungrounded, there is capacitance to ground from each of the phases.