A Novel Directional Algorithm for Transmission Line Protection Based on Least Squares Optimization

Directional protection is a crucial function in advanced transmission network relays. In this paper, a novel directional algorithm for transmission line protection is presented. Proposed algorithm responds to all kind of faults accurately without any dead zone. In this scheme, discrimination between internal and external faults will be done precisely even for close relay faults. The proposed algorithm utilizes a close form equation achieved by least squares optimization. Directional protection function is carried out based on proposed algorithm under various conditions such as current transformer saturation, power swing and source capacity changes. Moreover, variation on some parameters such as fault inception and fault resistance has only negligible effects on algorithm performance. Due to employing of low sampling frequency, hardware implementation of the proposed algorithm is not complicated. Algorithm performance is evaluated by applying the field data from Manesht 230kV substation located at Ilam province as well as extracted data form EMTP-RV simulations. Simulation results verify the speed and reliability of the proposed algorithm.