Fault Analysis of Single - Phase Grounding of Three - Phase 4PT Voltage Transformer
In 10 kV and 35 kV ungrounded systems, single - phase grounding faults cause minimal current, so protection rarely trips. Per regulations, operation is limited to 2 hours; prolonged undetected faults may worsen, even damaging switches. While the State Grid promotes small - current grounding line selection devices in 110 kV and 220 kV substations, their accuracy remains low, requiring monitoring/operation staff to analyze remote measurements. For ungrounded systems with three - phase 4PT voltage