Abstract:

This paper introduced and analyzed the coupling mechanical DC circuit breaker and its self-protection strategy which used in the 160 kV Nan’ao flexible HVDC project,after then,a self-protection strategy for DC circuit breakers based on the fracture CT zero drift criterion was proposed.The corresponding simulation model was built based on the PSCAD/EMTDC simulation platform,and the impact of the fracture CT zero drift value selection was carried out.Based on the DC circuit breaker of the Jin’niu converter station refusal-to-open fault,when an artificial negative-pole to ground short circuit experiment implemented in the Su’cheng confluence line,the impact of the CT zero drift value criterion on the circuit breaker self-protection strategy and the actual system operation was analyzed.Finally,a CT zero drift correction method was proposed to solve the refusal-to-open fault of Jin’niu DC circuit breaker,and the effectiveness of the proposed method was verified by experiments.

Key words: flexible HVDC transmission system, coupled mechanical DC circuit breaker, CT zero drift value, DC circuit breaker failure