Optimal Coordination of Directional Overcurrent Relays using Numerical Iterative Method

There has been an emphasis on improving the resiliency of the power grid by decentralizing power generation and developing self-healing grids. Despite its potential to enhance distribution system resiliency, increased integration of Distributed Energy Resources (DERs), both generation and storage, in the distribution network presents significant challenges. One of these challenges is the possible misoperation of the traditional distribution protection system; for example, false tripping can occur due to bidirectional power flow and change in network topology. A study of the protection system has become an indispensable part of the decentralization of energy generation; in order to maintain the reliability and security of the network, there is a need to modify the protection system in terms of its elements and their coordination. This paper focuses on improving the coordination of protection devices in a distribution network with DERs and presents a mathematical formulation to coordinate directional overcurrent relays. Time Dial Settings (TDS) and pickup current are first solved by a linearized-iteration method. Then, a particle swarm optimization-based approach is presented to determine these coordination settings such that the minimum relay operating time is achieved. Both approaches are tested on a distribution test system and simulated on a virtual real-time environment