A new protection scheme of grounding electrode line of UHVDC based on injection method

In view of the refusal problem of the existing UHV DC grounding electrode line impedance monitoring system, the expression of the fault impedance under different short-circuit fault conditions of the ground electrode line is theoretically derived. The reason for existing of dead zone is explained. To improve the performance of grounding electrode line, a novel protection scheme is proposed. The proposed protection scheme using transverse differential principle. Compared with the conventional protection scheme, the dead zone can be decreased obviously. To verify the reliability of the proposed protection, a simulation model `is built in EMTDC/PSCAD according to parameter of real UHVDC project. The feasibility of the proposed scheme is proved according to the simulation results.