Phase Related Current Differential Protection of Three-Terminal Transmission Lines

Abstract

T-Type transmission lines are widely used in HV power system. The paper analyzes operation characteristics of fault component based traditional differential protection principles in the complex plane. The paper pointed out that there are some limitations for traditional principles in ensuring sensitivity of internal fault and reliability of external fault. Furthermore, the paper proposes a novel principle for T-type transmission line. Current phase differential phase is introduced into realization of current differential protection. Restraint unit of the proposed principle takes the role of drive and restraint respectively in the case of internal and external faults. Therefore, both the sensitivity and reliability of protection are improved significantly. At last, simulation tests show that the proposed principle is valid.