Lightning faults of DC dry-type air-core reactor in HVDC substation

Abstract

Dry-type air-core reactors of DC filter are important Equipments in HVDC converter stations. Four abnormal noises occurred in the pole II DC filter field of a ± 800kV converter station of china in 2020. The video monitoring shows that the dry reactor area has discharge, and the turn to turn insulation damage of dry-type reactor is found during power outage maintenance. According to the lightning location system, lightning falls at the four times of dry reactor discharge in the channel of DC transmission line. The fault recording of DC bus and DC filter shows that bipolar bus intrudes into lightning wave at the time of reactor discharge, so it is determined that reactor discharge is induced by lightning. Since arresters are paralleled on both ends, and L1 both ends withstand voltage not exceeding the design value, so the first turn-to-turn discharge shall be caused by insulation deterioration. Transmission lines of HVDC system are generally long, Equipments of converter station frequently subject to lightning intrusion. Research related to insulation aging under this working condition shall be strengthened.