Simulation Research On Lightning Overvoltage And VFTO Of 500kV Booster Station In Hydropower Station With GIL Outlet

To solve the issues of energy shortage and environmental pollution in today's society,constructing large hydropower stations has become an increasingly valued solution.As a result,hydropower stations are more important by expanding their proportions in energy structure.Subject to geographical constraints,hydropower stations are often accompanied by booster stations.In addition,due to the limitation of the insulation material technology,the safety margin of the electrical equipment with the higher voltage level is less.Therefore,the overvoltage problem facing the high voltage boost station,especially lightning overvoltage and very fast transient overvoltage(VFTO)with high frequency concerned by this paper,is directly related to the safety and reliability of hydropower stations and even the power system.The electromagnetic transient program ATP-EMTP is taken as the calculation tool and Suki Kinari hydropower station in Pakistan is chosen as the simulation object.According to the actual parameters of the hydropower station,the corresponding high-frequency equivalent model for each type of electrical components in the station is established.On this basis,the simulation conditions are set in a strict way.By analyzing the simulation results,distribution rules of lightning overvoltage and VFTO under different conditions are discussed,and the validity of the insulation coordination scheme of this boost station is verified.It is of great importance to other similar 500kV boost station of hydropower station.The results show that:First,GIL is usually laid between GIS and overhead lines,which is advantageous both for repressing the lightning overvoltage and VFTO,compared with other ordinary substations.Second,if arresters are installed on the line entrance side busbar and the transformer side busbar,the safety of insulation to the ground can be ensured.Third,operation mode of the boost station is an important factor affecting the lightning overvoltage.The simpler the network topology is,the higher the lightning overvoltage at the same location.Fourth,characteristics of VFTO are also related to the structure and length of the live busbar before opening the DS.When the length of charged busbar is short and the number of parallel devices is large,the high-frequency component of VFTO is concentrated,which indicates that VFTO's amplitude is higher.On the contrary,although the damping radio increases,the initial steepness of VFTO also increases,which means the interturn insulation of coil device requires to be reinforced.