Relay Protection Of Distribution System With Distributed Generations

Distributed generation is an environmentally friendly, efficient, and flexible power mode which has been widely concerned at home and abroad. Our country has established a number of distributed power station, plan to2020, distributed energy installed capacity reached50000thousand kilowatts. With the large number of Distributed generation access distributed power, the single power supply and traditional distribution have been changed, power flow and shortcircuit current distribution have been changed have an impact on theoriginal configuration of the relay protection.This paper introduce the characteristics of distributed power supply firstly, then study several common types of distributed power supply, research the equivalent model and access in the form of the distribution network which distributed generation access in. Introduced the principle of the distribution network of the three-current protection configuration, establish the mode of distribution network system without DG, the mode of distribution network system with DG, equivalent circuit mode of distribution network system without DG, equivalent circuit diagram of distribution network system with DG. Based on these models, derived for three-phase short-circuit current value expression, comparison of two models of short-circuit current value, analysis on the original configuration of protection effect, analysis the mode of auto-reclosing and correctness of the theoretical analysis is verified by PSCAD/EMTDC simulation.In view of the impact of distributed power distribution network protection, To mitigation the impact of DG interconnection, this paper put forward a penetration level calculation method with considerations of short-circuit current constraints, established a single DG and multiple DGs access model, Derived constraint conditions, Particle Swarm Optimization is applied to solve the objective programming, the feasibility of the method proposed is shown by an example of a33-bus distribution system.Finally, A new protection scheme based on the coordination of zoned pilot protection and overcurrent protection is introduced. The protection principle is tested, the traditional protection profile was improved, the results have proved its effectiveness by PSCAD/EMTDC.