10-04-2017, 09:16 PM
Abstract
This paper presents genetic algorithm (GA) method for coordination of overcurrent (OC) relays. The OC relays are the major protection devices in a distribution system. OC relay is usually employed as backup protection. But in some situations it may be the only protection provided. To reduce the power outages, mal-operation of the backup relays should be avoided, and therefore, OC relay coordination in power distribution network is a major concern of protection engineer. The OC relay coordination in ring fed distribution networks is a highly constrained optimization problem. The purpose is to find an optimum relay setting to minimize the time of operation of relays and at the same time, to avoid the mal-operation of relays. This paper presents GA technique for optimum coordination of OC relays in a ring fed distribution system. Constraints are incorporated in the fitness function making use of the penalty method. Computer programs (using MATLAB) have been developed for optimum coordination of OC relays using GA technique.
Introduction
In conventional methods coordination of Over Current relays (OCR) is obtained through careful time grading. Due to the expansion of electric systems, the need for an efficient coordinated protective system is crucial. The optimal time for protection given the coordination problem turned to be little complex to be calculated. To solve the problem of the coordination of OC relays, Genetic Algorithm (GA) technique is applied. The purpose of the OC relay coordination is to find an optimum relay setting to minimize the time dial setting (TDS) and calculate the pick up current (Ip). Setting of the relay is the core of the coordination study to satisfy the primary and secondary operation. This paper presents an application of GA technique for optimal coordination of OC relays to a 6-bus ring system.For optimal co-ordination of over current relays, linear programming techniques such as simplex, two-phase simplex and dual simplex are used. Another way of optimal coordination program is using artificial intelligent system such as genetic algorithm (GA). In this paper, a powerful optimal coordination method based on GA is introduced. The objective function (OF) is developed to solve the problems of mis co ordination and continuous or discrete time setting multiplier (TSM) or time dial setting (TDS). In other words; the novelty of the paper is the modification of the existing objective function of GA, by introducing a new parameter and adding a new term to OF, to handle mis co ordination problems both for continues and discrete TSM or TDS. The method is applied to two different power system networks and from the obtained results it is revealed that the new method is efficient, accurate and flexible.