A new technique for setting calculation of digital distance relays

It is known that the protection system is one of the important parts of the power system. So one can say that it is the most important one. The protection system can be accepted if and only if it is efficient one and realize some requirements. The protection system must have high reliability, high selectivity, high speed and low cost. During the calculation of operation setting for different protection zones of the distance relays, some problems have been raised. The urgent one is the overlap, which may occur for the same protection zone. This problem reduces the selectivity of the protection system and causes more than one relay to operate at a time to clear the fault. This means that healthy parts from the power system will be isolated to clear the fault. This paper aims to overcome the problem of the overlap using a new computer program designed for this purpose. This program is aimed at calculating the setting values for the different protection zones of the digital distance relay. It is known that there are many rules for the distance relay setting. The proposed computer program can be used for any protection system using any setting rule without any overlap. During any fault, only one relay will operate to clear the fault in its protection zone. Subsequently, the only faulty part from the power system will be isolated to clear the fault. This ensures that the selectivity of the protection system and the reliability of the power system enhances.