Research On Effects Of Distributed Generation On Distribution Network Protection And Countermeasures

Distributed Generadions have a good market prospect for its flexibility, environment effects, economics and other factors. The access of DGs to distribution network power network structure, protection network changes the network structure and influences the protection to some extent.The access of the DGs to the network is the key for DGs’development.Based on the actual network structure, the influence of the access of distributed generations to the the distribution network protection is analysed, of which the conclusion is that the DG produce a great impact on the protection of the downstream in the network,which makes the protection lose selectivity and the protection area of the downstream current quick-breaking protection extends to the next line.Because of limitations of current protection in distribution system with distributed generation, the paper applies adaptive protection to distribution network. In order to reduce the impact of distributed generation to protection, according to structure of distribution system with distributed generation and symmetric component algorithm, an adaptive protection algorithm based the phase differential current fault component can be achieved. The algorithm collects data of postfault and before the fault occurred. It can identify the fault. The model of distribution system with wind turbines is developed in the MATLAB environment. Results of simulation verify the algorithm can eliminate the impact of distributed generation in distribution system and reflect a fault can be identified as internal or external.The paper applies distance protection to distribution network. Results of simulation verify distance protection making up the loss of current protection. But it can cause some problems when distance protection applied to distribution system, especially the effect of transition resistance. The paper focuses on the effect of duplicate supply with transition resistance. In order to reduce the impact of transition resistance to distance protection, in this paper, sequence component algorithm can be achieved. The algorithm collects current and voltage values. It is not influenced by the transition resistance and can measure fault impedance. The model of distribution system with wind turbines is developed in the MATLAB environment. Results of simulation verify the algorithm can eliminate the impact of the transition resistance from the protection, accurately reflects the positive sequence resistance from the point of failure to protection device.This paper proposed2novel protection schemes based on the relations between the positive sequence, negative sequence and zero sequence quantities of faults.These schemes eliminate the influences of the DGs on Distribution network whcih are economic and avoid the ivest on the modification of the existing protection system.