Digital Relay Performance During Power Quality Disturbances

Abstract

This thesis investigates the impact of power system disturbances on the performance of digital protective relays. The study relies on simulating the transients generated from the power system disturbances using Power Systems Computer­ Aided Design software (PSCAD). The implementation of the digital relay algorithms and the evaluation study has been carried out using MATLAB. Four power system disturbances have been considered for this research: System frequency deviation, transfonner energization, power factor capacitor bank switching and transmission line shunt capacitance switc ing. For each disturbance, the suitable power system configuration is selected. The operating conditions are adjusted in order to operate the protective relay under severe conditions close to its setting value. Four algorithms are used to perfonn the digital relay function; namely: Fourier full cycle, Foruier half cycle, approximate Walsh method and true root mean square algorithm.