DISTANCE RELAY PROTECTION OF AN 11 kV DISTRIBUTION SYSTEM PERFORMANCE ENHANCEMENT USING MICROPROCESSORS

Transmission and distribution lines are protected against fault in power network using protection methods and distance relays. This work focused on enhancing the speed of isolating defective circuits from the network by employing a microprocessor to minimize tripping time of the relay. The microprocessor was programmed with the help of information from network-wide fault research. Through the application of Power System Computer Aided Design (PSCAD) software simulations, the designed system's operating time for a line-to-line (LLG) fault between lines ABG occurring at 35 km on the tested line with a fault impedance of 5 Ω was 5.4 ms, while the old system, which was the conventional distance relay system without a microprocessor, had an operating time of 15 ms. In actuality, it was discovered that the new protective mechanism utilizing the microprocessor increased the average operating speed of the distance protection scheme from 6.144 ms to 4.390 ms, leading to boosting around 28.5% in the operating speed or speed of isolating the malfunctioning circuit. Also, the average tripping accuracy was improved from 67.5% to 100% for the developed system which shows 48% increase in accuracy.