Performance Evaluation of a MHO Distance Relay on the Benin–Egbin 330 kV Transmission Line Using MATLAB/Simulink

Distance protection serves as the primary support system for high voltage transmission line protection due to its speed, selectivity, and relative independence from fault current magnitude. This study analyzes the performance of an MHO relay on a 330 kV transmission line under various fault conditions to identify factors influencing its reliability and to propose optimization strategies for improved protective relay operation. A simulation-based approach was employed to determine line parameters, including resistance, inductance, capacitance, and length, which are consistent with values reported in previous literature. These parameters informed the development of an accurate Simulink model of the Benin-Egbin transmission line. The Simscape Electrical environment was utilized to model the MHO distance relay, incorporating all critical conditions necessary for zone discrimination. The system model included single line-to-ground, line-to-line, and three-phase-to-ground faults at varying distances. R-X plots were evaluated to check relay performance, while voltage and current waveforms were assessed for pre-fault and post-fault behavior in this study. The results revealed that the single line-to-ground, line-to-line, and three-phase-to-ground faults operated accurately with the MHO distance relay under normal fault impedance conditions, which are very suitable for distance protection applications. Furthermore, it was found that performance degradation occurred under high fault -resistance conditions, and this was the same spot at which reaching was observed. Thus, adaptive or impedance-compensating algorithms are required to improve protection accuracy.