Optimum Coordination of Overcurrent Relays in Distribution Systems Using Big-M and Dual Simplex Methods

This paper presents Big-M method and Dual Simplex method for optimum time coordination of over current relays in a distribution network. These methods are used to find the optimized values of time multiplier settings (TMS) of relays using linear programming problem (LPP). Objective function contains artificial variables in Big-M method. Dual simplex gives the optimum solution without introducing any artificial variables. Over current (OC) relay plays a major role in power distribution system. It protects electrical power systems against excessive current which are caused by faults like short circuits, ground faults, etc. The fault is cleared within a least possible time. Big-M and Dual simplex technique are presented in this paper for optimum time coordination of OC relays in a radial fed distribution system.