The Research Of UHVDC Commutation Failure Impact On Relay Protection

UHVDC has brought great benefits to the power grids, but also makes the power grid operation becomes very complicated. Especially after the Commutation failure happened The inverter side of converter station in the AC/DC hybrid system;It will lead into non characteristic harmonic to the AC system and affect the performance of relay protection system;even lead to the misoperation of harmonic blocking criterion and caused the Extension of the action time when a minor fault was happened.It also increase the possibility of damage to the equipment.To solve this problem, This paper analyzes the process of commutation failure in the DC system inverter side of converter station and study the impact on the widely used Relay protection such as the distance protection using power frequency fault components, the jump-value of current direction relay and The zero sequence current phase comparison pilot protection.the simulation shows that UHVDC commutation failure caused refuse operation of the distance protection using power frequency fault components when the internal fault happened; Impact on the ability of accurately judge the fault direction of the jump-value of current direction relay, caused refuse operation when the internal fault happened and Miss judge fault direction in the Outside the region. When The zero sequence current phase comparison pilot protection used in the UHVDC system can Accurate the internal,external fault and has been no impact on commutation failure.