Aiming at the fast selective isolation problem of direct current(DC)line fault in DC circuit breaker application

the fault elimination strategy of symmetric single-pole voltage source converter based multi-terminal direct current(VSC-MTDC)transmission line is studied. The characteristics of single-pole-to-ground fault and pole-to-pole fault are analyzed

and the same cosine attenuation characteristics of the fault current changing rate in the early stage of single-pole-to-ground fault and pole-to-pole fault are obtained. A directional line selection strategy based on current changing rate

and the scheme for fault isolation and fault elimination using DC circuit breaker and reclosing strategy are designed respectively. The characteristic of fault current changing rate in the single-pole-to-ground fault and DC fault elimination strategy are verified based on PSCAD/EMTDC. Simulation results demonstrate the validity of the current changing rate characteristic and the effectiveness of the designed strategy for the elimination of the fault.