MICROPROCESSOR BASED 3 STEP QUADRILATERAL DISTANCE RELAY FOR THE PROTECTION OF EHV/UHV TRANSMISSION-LINES

This paper deals with the development of a 3-zone quadrilateral distance relay for the protection of EHV/UHV transmission lines. The proposed scheme is based on the Fourier Transform method of extracting the fundamental components of voltage and current signals from non-sinusoidal post fault signals.[1] The determination of the quadrilateral characteristic is completed through software. The relay is successfully tested for a number of different three step quadrilateral characteristics and the results are obtained. Any quadrilateral characteristic can be obtained. Recommendations are made to use 16-bit processors to reduce the operating time and for better accuracy.