Research on Fault Detection and Protection Strategy of HVDC Circuit Breaker Based on New Criterion

Increasing the breaking speed of the HVDC circuit breaker in the DC grid can provide an additional necessary time for other control strategies of the VSC-HVDC system during fault conditions. This paper presents a new fault local detection and power line protection control strategy for HVDC breakers based on Zhangbei four-terminal flexible HVDC transmission project. This method determines if the line has faults by monitoring the rate of change of voltage (ROCOV) at both ends of the DC line. And this method can realize fault local judgment and improve the speed of protection operation. In addition, the method of distinguishing the faults of adjacent lines, busbars and local lines is specifically proposed, and the accuracy of the proposed method and the selectivity, reliability and speed of protection actions are verified by PSCAD under different working conditions. For a flexible HVDC system which needs to quickly clear the fault, this method provides a new research idea for rapid self-breaking control strategy of DC circuit breaker.