Abstract: Aiming at the problems of long-time consumption,large power out-age range,and power loss of the converter fault isolation and restart process in a UHVDC project,an optimized strategy was proposed based on the analysis of the fault mechanism.On the one hand,the converter protection area,as well as the connection mode of the breakers is optimized,and fast circuit breakers are added to speed up the process. On the other hand,the fault isolation and restart strategy is improved. By using the inverter phase shift control to limit the fault current fast,using fast circuit breaker action to narrow the scope of fault isolation,the occurrence of pole isolation,pole restart,and large-scale machine and load shedding is avoided. The simulation verification shows that the optimized fault isolation and restart strategy takes less than 0.5s in total,and only isolates the faulty converter to ensure the continuous power transmission of the sound part,which significantly improves the reliability and economy of UHVDC transmission.