High voltage capacitor ground fault

The ground fault of the high voltage capacitor has a great impact on the stable operation of the DC transmission system. The DC filter high voltage capacitor ground fault protection method has problems such as poor selectivity, low sensitivity, and difficulty in setting the value.

1) Poor selectivity. When a ground fault occurs at different positions on the high voltage capacitor, the currents collected by the protection vary greatly. In the same fault point, the current magnitude varies greatly under different system operating conditions. Differential protection and grounding protection cannot distinguish the ground fault of the high voltage capacitor. Location and severity, protection action selectivity is not guaranteed.

2) Low sensitivity. Under certain conditions, the high-voltage capacitor has a ground fault, and the differential current and the unbalance current are small, which cannot meet the protection operating conditions.

3) The setting of the setting is difficult. The protection of the ground fault of the high-voltage capacitor needs to select the alarm or trip according to the severity of the fault. The setting of the grounding protection used in the UHV project is completed by the engineering dynamic simulation test. This method can not cover all operating conditions of the system, and the setting is not completed. The setting has a certain randomness and consumes a lot of manpower.