Intelligent distance to over current relay coordination in sub-transmission networks

Sub-transmission power networks are primarily protected by distance relays and over current relays are used as backup relay due to their poor operational speed. Coordination of distance to over current relays is achieved in this research paper by optimally selecting the over current relay parameters which constitutes relay time-inverse characteristics and relay parameters and zone-2 setting of distance relays. Solving such type of combine distance to over current relay coordination problems is tedious job using the conventional optimization methods. Therefore an evolutionally based optimization techniques is applied in this research paper which selects the optimal over current relay parameters, user defined time inverse relay characteristics and zone-2 settings of the distance relays