Improved Transmission Line Relay Algorithm Based on Signum Function of Incremental Currents

Abstract

Transmission lines are a key part of the power system because they carry power from one end to the other. In case of a fault, the power transfer is perturbed, and the equipments on generation side as well as on the load side can get damaged. Transmission lines carry power from generation end to load end, so it is very important to keep the transmission lines protected. A swift protection system is necessary for the power system. For a quick protection system, rapid fault detection is crucial. A novel method for detecting as well as classifying the faults on transmission lines is reported in this paper. The direction of incremental current along the transmission line's two ends forms the base of this technique and uses a modified signum function. The effectiveness of the said technique is validated by simulating signals in a PSCAD/EMTDC environment on a 50 Hz, 230 kV, 5-bus network. The parameters considered in this study are the line loading, DC offset, fault location and the fault resistance (FR). The FR values considered for simulation purposes range from 0.01 ohm to 1000 ohms. Two types of line structures have been adopted, viz., first, a line connecting generator bus (PV bus) to a load bus (PQ bus) (L_GL) and second, a line connecting two generator buses (L_GG). Detailed results of this study show that the relay detects all internal faults with different loading levels and various FR values. The maximum operating time of the relay is ascertained as 4 ms. The technique has also been validated on IEEE 30-bus system.