Analysis of the Misoperation of Differential Protection Caused by the Open Circuit of the Neutral Wire in the CT Secondary Circuit

In this paper, an event of the misoperation of the differential protection for a transmission line is analyzed. The cause of the event is the open circuit of the neutral wire in the CT secondary circuit, which results in the distortion of the current waveform collected by the line protection on one side when an out-of-zone fault occurs. A difference in current is generated between the two sides, thereby triggering the misoperation of the protection. The accident process is introduced in combination with the on-site waveforms. The causes of the accident are analyzed, and a simulation model is established using Simulink. The simulation results verify the correctness of the analysis.