Study On The Protection Scheme Of Distrinution Network With Micro Grid Based On Subdivision Strategy

With the connection of DG,the power distribution network has changed and becomes a double sources network.Tradition current protection suitable for tradition distribution system may not meet the demands.In order to ensure the stability of power system,it is of great significance to study the improvement scheme of protection.The paper analyzes the influence to the protection when DG connected to the power distribution network,and put forward a improvement scheme.The paper analyzes the necessity of developing DG in shenzhen.It is because of the advantages that DG in relieving the pressure of peak load and frequency regulation,and improving power supply reliability.The paper analyzes the influence to the protection when DG connected to the power distribution network.When the fault occurs in the downstream area of the DG connection node,the downstream current increases will cause the current ? mis-operation.The upstream current decrescent will cause the protection refuse action.When the fault occurs in the upstream area of the DG connection node,the upstream current increases will cause the protection refuse action.When the fault occurs in the adjacent feed line,near the system side's current increases will cause the protection mis-operation.Verify the correctness of the analysis by using PSCAD/EMTDC software established simulation model.In this paper,a new protection scheme based on the coordination of zoned pilot protection is introduced.Directional pilot protection is configured at the upstream side of DG,and the overcurrent protection is retained for the whole feeder.Definite time-lag current protection or inverse time current protection is configured at the downstream.Then verify the correctness and feasibility by using PSCAD/EMTDC software established simulation model.