REAL-TIME ASSESSMENT OF A SYMMETRICAL COMPONENT AND MICROCONTROLLER BASED DISTANCE RELAY

This paper presents the design, implementation and real-time assessmen t of a microcontroller based digital distance relay that can be used f or the protection of power transmission lines. The proposed design is implemented using a general-purpose Intel 8097 microcontroller and cus tom-made filters, operational amplifiers, sample-and-hold amplifiers, multiplexers, and analog-to-digital converters. The relay software is based on a computationally efficient symmetrical component based fault distance estimation algorithm. Results of the performance assessment studies on this algorithm have shown promising fault distance estimate s for first-zone faults on the protected transmission line. Real-time implementation of the symmetrical component based fault distance estim ation algorithm is presented and discussed in this paper. Hardware and software tools were used to design and fabricate a microcontroller ba sed distance relay using the above-mentioned algorithm. This paper des cribes details of the design of the distance relay. A test setup in th e laboratory using a transmission line model was used to generate data to assess the real-time response of the designed relay. High-speed re lay operation of the order of one cycle is demonstrated in the test re sults.