POWER SYSTEM DISTANCE RELAYING USING PC AND OPTICAL CHANNEL

Abstract

This dissertation presents a PC-XT based quadrilateral istance relay suitable for protection of high voltage lines. The igital signal (of sampled voltage and current waves and control ignals) is transmitted using duplex optic-fibre link. To realize distance relay operation, equidistant samples of oltage and current are taken, and based upon that effective esistance (r) and react;ance (x) values are determined. Then hey are tested for lying in characteristic relay operating zone, enerating appropriate control signals. This operating uadrilateral zone characteristic can be easily changed by feeding n new parameters. Three versions of the relay have been developed in the resent work and their comparative performance evaluated. In the first version three samples after each zero crossing f voltage wave have been taken [ plot 3.1 ]; but this gave much rror in the calculated r & x values. In another version, six samples were taken after each oltage zero crossing. There was 50% redundancy leading to much ess error in the r & x values. [see section 3.2.3 & plot 3.2 ) When the above six sample version results were found atisfactory, the samples were taken continuously after an nitialization process of fetching six samples after a zero rossing. The samples were fetched continuously at the interval f 1.5 ms. r & x values were calculated using the latest six amplest discarding the older ones. This reduces the time delay f relay operation. Plot 3.3 shows continuous samples being taken nd section 3.3 explains the process.