Analysis and Improvement Measures for a 66 kV Shunt Capacitor Fault

The fault of the shunt capacitor device in a 220 kV substation led to the 66 kV bus outage and the total shutdown of six 66 kV substations. In order to find out the specific cause of the fault and avoid the recurrence of similar problems, analysts conducted a comprehensive analysis and judgment on the capacitor fault process and causes from various aspects such as protection action, setting calculation, disassembly inspection and harmonics. Through analysis, it is determined that the reason for the expansion of the accident is the mismatch between the shunt capacitor bank unbalance protection current transformer and the protection device. In view of this accident, the corresponding measures and suggestions are put forward from the aspects of optimization protection setting principle, bridge difference current transformer transformation, etc., which is of great significance to improve the operation reliability of this type of shunt capacitor device.