The optimal coordination of over-current relay protection in radial network based on Particle Swarm Optimization

Making a robust and reliable power system with coordination of over-current relays (OCRs) is a big challenge for relaying engineers. Various type of programming optimization techniques are frequently used to find best optimal relay settings of over-current relays in modern distribution systems. The goal of this paper is to discuss optimization of over-current relays coordination for internal faults protection over transmission lines in radial network via Particle Swarm Optimization (PSO), which is one of the capable heuristic techniques to solve constrained optimization problems. PSO algorithm objective is to achieve proper coordination between each main and its back-up relays. Based on the variables obtained during normal operation and three phases' faults conditions from DigSILENT software simulation on IEEE 15 nodes radial system, PSO algorithm is applied to properly identify suitable relays settings namely Time Multiplier Setting (TMS) and Plug Setting (PS) for all Inverse Definite Minimum Time (IDMT) over-current relays. The collected data are conveniently examined using the PSO algorithm implemented in MATLAB. The obtained TMS and PS settings of each relay show the effectiveness of the proposed PSO technique in terms of accuracy and speed in a large scale radial network configuration.