Optimal method for mal-function for protective devices in distribution systems interconnected with PV systems

This paper deals with the optimal countermeasures for the mal-function of protective devices at primary feeder in distribution systems when new power sources like photovoltaic (PV) systems are interconnected, based on the symmetrical components of short circuit studies. When new power sources are considered to be interconnected to distribution systems, bi-directional power flow and interconnection transformer connection of new power sources may cause the operation problems of protective devices (mainly re-closer), since new power sources can change typical characteristics of distribution systems. Therefore, this paper shows an analysis skill of the mal-function mechanism of protective relay and proposes the optimal solution for the mal-function problem using the symmetrical components of fault analysis. And, also this paper shows the effectiveness of proposed method by the simulation at the field distribution systems.