Research on An Incorrect Operation of Grounding Transformer Protection and Its Improving Measures

This paper analysis a mal-operation event of grounding transformer protection under arc-suppression coil grounding in parallel small resistance grounding mode. By analyzing the zero-sequence current distribution within substations under the special operation conditions, the paper concludes that the reason for mal-operation is unreasonable protection configuration can not adapt to the special operation conditions. The conclusion can provide guidance for the design, installation, relay setting calculation and acceptance testing of grounding transformer protection.