Fuzzy Logic Overcurrent Relay Using Sugeno Technique

The overcurrent relay is the simplest and most economical type of protective relay, the relay is designed to operate when more than a predetermined amount of current flows into a particular portion of the power system. Time delay between relay's main zone and it's backup will keep the selectivity of the system, The inverse definite minimum time relay will calculate the time delay inversely proportional to the fault current level. This technique has some weaknesses where the time delay provided for a given case maybe too high and if the fault is not isolated immediately then damage could be caused to other connected equipment in the power system. This paper presents the fuzzy logic relay using Sugeno technique to determine the time delay, and using of symmetrical components application in detecting fault type, also it presents a comparison between times calculated by other techniques.