Optimum coordination of directional overcurrent relays in a distribution network with distributed generation

Abstract

The conventional relay protection coordination method is mainly used in the industry to calculate the protective overcurrent relay settings. The conventional method requires many inputs and does not produce the best relay coordination results. When there are multiple sources, the calculation process becomes even more complicated and cumbersome. In order to optimize the coordination results of the interconnected network with multiple sources, the particle swarm optimization algorithm is proposed in this research. Optimization algorithms have been applied to many engineering problems. However, few researchers have applied particle swarm optimization to the coordination problem especially in power systems with distributed generation sources. The objective of this research is to propose a particle swarm optimization algorithm to improve on the protection settings for a distribution network with distributed generation sources as calculated by the conventional method. The proposed particle swarm intelligence algorithm is compared with the conventional method by making use of two case studies. The IEEE1 8-bus test case consisting of a total of 14 primary relays and 20 relay pairs is used. Relay pairs are identified and set, determining the primary and back-up relays in each pair. Three-phase faults are simulated at 5% of the protected line. The operating time of the primary relays is calculated by randomly selecting the time multiplier settings, fixed pick-up currents and simulated three-phase fault currents. The coordination time interval of 0.3 seconds is used. Based on the coordination results obtained in this research, the proposed particle swarm optimization algorithm can be used to calculate the settings of the directional overcurrent relays in a distribution network with distributed generation. The proposed algorithm has shown to have the ability to maintain selectivity between the relays being coordinated and minimize the operating times of the primary relays for close-in three-phase faults