Modeling and Validation of a Directional Overcurrent Relay as an Island Interconnection Device

Abstract

The growing number of decentralized generators in the distribution systems and the consequent increase in the penetration level in the networks have prompted the inclusion of this scenario in researches involving the planning of electrical power systems. The planning of protection systems for distribution networks considering distributed generators requires adaptations in the approach due to modifications in characteristics of the network, such as passivity and unidirectional power flow. Furthermore, the insertion of generators in distribution networks allows the implementation of new operation methods, such as the possibility of disconnecting some loads from the main feeder and supplying them through distributed generators. The island operation can improve the service continuity indexes, as well as reduce the costs of non-supplied energy. Although the island operation is widely proposed in the literature as a means to improve the system's reliability, the simulation of a protective device to intentionally island a region and the verification of its limitations is not. In this paper, we present the modeling of a directional overcurrent relay through ATP-EMTP, and its employment as a device for island interconnection, analyzing its zone of non-operation. CIGRE 14-bus test system is used to conduct short-circuit tests with the variation of resistance and type of fault applied. Theresults show the effectiveness of the device, which is able to identify all faults with real impact on the network, placing the region in island operation in less than 20 ms.