Study Of The Impact Of DG On The Protection Of Distribution Network

As one kind of efficient, economical and reliable energy, Distributed generation (DG) have been attracting intensive attention at home and abroad recently. The fast development of DG has brought new challenges and influences to traditional power systems. Most distribution systems especially rural systems are operated in a radial configuration, and the protection of distribution systems are based on this configuration. Installation of DG will not alter the topology of the system, but the power will be able to flow in multiple directions. This fundamental change in operating principle can restrict the operation of the protection system causing false tripping of feeders, blinding of protection and increased or decreased fault levels.This paper firstly introduces the protection system and feeder automation technology of distribution network. On these bases, typical distribution systems model and DG model are built. And then the paper analyzes the effect of the size and location of DG on the relay protection and automation of the distribution network.The interconnection protection of DG is discussed in this paper. The author analyzes the major impact of interconnection transformer connections on interconnection protection and the island detection methods of DG. Then the paper elaborates on the proper required protection and how its operation will prevent undeired consequences to DG and distribution network. The required interconnection protective equipments are presented on the basis.To mitigation the impact of DG interconnection,the paper put forward a penetration level calculation method with considerations of short-circuit current constraints. The short-circuit calculation of distribution network with DG addition is analyzed,then the penetration level calculation models are established for single DG and multiple DGs interconnection respectively. In this paper, the niche genetic algorithms is applied to solve the objective programming. The feasibility of the method proposed is shown by an example of a 34-bus distribution system.