Modified Communication Assisted Line Differential Protection Scheme With Seen Reactance and Drift Current Based Back-up

Although line differential protection schemes have superior fault sensitivity and speed of operation, their dependency on pilot signals introduces certain challenges. These challenges include nuisance trips due to intolerably high communication delay and loss of fault sensitivity in the event of communication link failure. Also, to incorporate potential mal-operation in the event of CT saturation, line charging current and marginal delay, higher restraining zones are set for line differential relay. Hence, sensing evolving faults with higher impedances is difficult with the differential principle. Considering these limitations, a novel seen reactance and current differential based approach is presented in this article. The proposed relay also acts as a backup in case of communication link failure. The seen reactance principle operates for the internal faults to the line. The reactance monitoring is found stable in various power system events such as dynamic variation in fault resistance, breaker arc restrike for the remote end breaker, and a High Impedance Fault (HIF) – shoot through phenomenon. The resistive reach of the proposed method is extended using current drift principle. The current drift principle is made stable by providing sufficient time delay for the operation. The tests are designed and carried out in PSCAD. The sensitivity of the proposed algorithm is tested in a scaled down hardware setup.