Analysis on the Causes of False Alarms of the Insulation Monitoring Device of the Medium Voltage System of the Nuclear Power Plant

Abstract

Insulation monitoring is crucial to personal safety and equipment operation in the power distribution system. However, two false triggering events of the same medium voltage insulation monitoring device occurred in the nuclear power plant. In this paper, the reasons for the two events are analyzed. The paper starts with the internal structure of the insulation monitoring device, analyzes the causes of the two false triggering events in detail, and draws a conclusion that the mismatching of neutral grounding mode of voltage transformer and insulation monitoring device in medium voltage system is the fundamental cause of insulation device alarm. At last, the improved suggestions for the insulation monitoring device of neutral point ungrounded system in nuclear power plants are given to solve the problem of false alarms.