| The worldwide energy crisis,the intensification of the power crisis and large-scale blackouts exposure the shortage of the grid.In order to make up for and improve the insufficiency of generation and transmission in large-scale centralized power systems.Distributed generation has become the focus of research.However,a large number of distributed generations access to to the distribution network,which has a certain impact on the traditional distribution network.In the paper,first,introducing the concept,classification,methods of grid connection and standards of distributed generation;analying several main types of DG in detail.Next,the article analyzes the influence of DG on the original protection of distribution network: discussing the impact from the location and capacity of DG access to and analysing the influences of DG on reclosing device too.Due to bidirectional power flow,assistant current and shunting effect caused by distributed generation,leading to the misoperation,refusing action and lower sensitivity of protection,bringing a big challenge to the safety and stability of distribution network operation.Finally,introduce the principle of adaptive current protection and the factors that affect the protection range,so an improved scheme for adaptive current protection is proposed.The proposed method can monitor the fault type and perform setting value online in this paper.Setting different values for the downstream and upstream of DG and checking selectivity and sensitivity for the new setting values.It also describes the coordination of protection at the double terminal power feeder and the adjacent feeder.The improved adaptive current protection can change the setting value online timely according to the change of power system operation mode and fault styles.Finally,through the Matlab software simulation,results prove that the improved adaptive current protection has the advantages for large protection scope,high sensitivity and good reliability. |
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