Injection principle based monitoring method of secondary circuit of zero-sequence current transformer in ungrounded distribution network

As the basis of grounding line selection in ungrounded distribution system, the zero-sequence current collected by zero-sequence current transformer is very important. By summarizing and analysing the abnormal problem of the secondary circuit of zero-sequence current transformer, a monitoring method of the secondary circuit of zero-sequence current transformer based on injection principle is proposed. This method can detect the secondary circuit without affecting the normal operation of the line, find the abnormal state of the circuit in time, and ensure the reliable operation of the secondary circuit. It effectively improve the correct rate of fault line selection in the ungrounded distribution network.