Impact of capacitive current of EHV/UHV lines on current differential protection

Based on distributed parameters line model, a current differential protection for extra high voltage and ultra high voltage (EHV/UHV) transmission lines is proposed in this paper. The distributed capacitance current in such lines has a severe negative impact on relaying of current differential protection. Thus the influence of distributive capacitive current on its protection during line to ground fault is carried out. In order to verify that current differential protection is influenced by capacitive current, capacitive reactance of transmission line is increased so that capacitive effect of line is reduced. An extensive simulation is carried out using PSCAD. The result shows that compensation of capacitive current in lines is necessary in proposed method to suppress its adverse effect on relaying of healthy phase.