Key Issues And Optimization Of Relay Protection For 110kV Substations With Distributed Generation

The global energy situation is becoming more and more intense.Renewable energy is receiving more and more attention.With the introduction of the concept of global energy internet,the proportion of distributed generation represented by photovoltaic power generation and wind power generation in the power grid has shown an increasing trend.Distributed generators have natural advantages in energy saving,environmental protection,flexibility and convenience,construction cost and sustainable utilization.However,due to the disadvantages of many objective factors and poor controllability,the access of a large number of distributed generators is bound to have a very serious impact on the relay protection of power grid,especially substations.According to the conventional practice The substation relay protection configuration may cause the relay protection and automatic device to refuse or malfunction,causing irreparable losses to the power grid.Therefore,it is very significant and far-reaching to study the optimal configuration of substation relay protection and eliminate the influence of distributed generation on relay protection for safe and reliable operation of power grid.In the analysis of the influence of distributed power supply on substation,the 110 kV Olympic substation of Liaocheng Power Supply Company is taken as the analysis model,and the configuration of conventional relay protection is analyzed.At the same time,the 110 kV system and 10 kV system of substation are analyzed according to the changes of multi-terminal power supply and power flow distribution brought about by the access of distributed power supply.The influence.Through the logic analysis of relay protection action when the fault occurs,the main reasons for the influence of distributed generation on 110 kV line protection,transformer protection,10 kV line protection and standby automatic switching device are obtained.The 110kV substation system is constructed based on PSCAD simulation software.The simulation provides reference for substation relay protection optimization strategy.In the research of 110 kV system relay protection optimization,taking the influence of distributed generation on 110 kV system as a breakthrough point,the corresponding solutions are put forward,such as distance protection and zero sequence protection,power direction protection and permissive direction pilot protection.The zero-sequence voltage distribution,short-circuit current calculation,logic analysis and other methods are used to analyze and demonstrate the solution strategy,and the optimal strategy of permissive directional pilot protection is determined.Then,according to the equipment parameters of 110 kV substation,the corresponding relay protection setting values are checked and adjusted,and the PSCAD simulation software is used to verify that the optimal strategy can solve the problem of non-synchronous closing of 110 kV line protection and zero-sequence voltage protection maloperation of transformer protection in 110 kV system.In the research of optimization of relay protection in 10kV system,aiming at the malfunction of lOkV line protection,the relay protection device is selective and directional.Through the analysis and comparison of various schemes,the optimal strategy of fiber optic current differential protection is proposed,and an optimal strategy of self-adaptive self-switching back-up function is proposed to solve the problem of device rejection.At the same time,the two transformation plans and intelligent components needed for the optimal strategy are studied and determined.Through PSCAD simulation software,it is verified that the optimal strategy can solve the problems of 10 kV line protection maloperation and backup automatic switching device refusal in 10 kV system.The research results of this paper will provide a reliable basis for solving the influence of large-scale access of distributed generation on relay protection of 110 kV substation,and provide an effective reference for the engineering transformation of 110 kV substation with distributed generation.