Study On Methods And Schemes Of Prevention And Control Of Geomagnetic Storm Disaster In Xinjiang 750kV Power Grid

The DC resistance of conductors of the 750kV and 1000kV grid per unit length is small,and the geomagnetically induced current(GIC)generated by the same geomagnetic storm on the 750kV and 1000kV grids is large;in addition,the rated operating current of the UHVDC transmission system with voltage levels of ±800kV and above is large.At present,the UHVDC adopted the method of setting series capacitors blocking device at the transformer neutral point to control the DC bias of the transformer due to the grounding current.Studies abroad have shown that the installation of a capacitors blocking device at the neutral point of the transformer to control the GIC will increase the risk of GIC biasing accidents at other stations.This paper study influence of DC Bias suppression of grounding electrodes on power grid GIC and its suppression schemes combining the DC bias suppression of Hami-Zhengzhou and Zhundong-Wannan UHVDC projects.The main research work and achievements of this paper are as follows:1)According to the DC bias suppression of the grounding electrodes of Xinjiang power grid,the GIC model of Xinjiang Power Grid was established,and the GIC of the grid before and after the input of the capacitor blocking device was calculated.The grounding electrodes bias suppression of±800kV Hami-Zhengzhou and±1100kV Zhundong-Wannan HVDC transmission project were analyzed and compared.It was concluded that the use of capacitor blocking device to control the DC bias of the grounding electrodes will increase the GIC value of some stations including the converter station,increase the fault of GIC of the transformer and the geomagnetic storm risk of the power grid.2)Considering the influence of DC bias of the grounding electrodes,the GIC biasing model of Xinjiang 750kV grid was established,and the NSGA-? algorithm was used to solve the Pareto optimal solution set.The GIC biasing suppression scheme for Xinjiang 750kV power grid considering the influence of Hami-Zhengzhou and Zhundong-Wannan UHVDC project is proposed.According to the theoretical calculation of the GIC value of the grid before and after suppression,the validity of the suppression schemes is verified.3)In order to using the GIC derived effect indicators to assess the geomagnetic storm hazard risk of the grid,the GIC-Q disturbance model of Xinjiang 750kV power grid was established,With the change of GIC-Q calculated by the GIC-Q disturbance model of the whole grid before and after the suppression,the effect of GIC suppression scheme of 750kV grid was tested.The results of this paper show that there are relatively few stations for grounding electrodes bias suppression of 750kV power grids for±800kV Hami-Zhengzhou projects and Zhundong-Hainan projects.The grounding electrodes bias suppression of the two projects has a relatively small impact on the GIC of the 750kV grid in Xinjiang,and has a relatively large impact on the 220kV grid.The paper proposes a suppression scheme for the GIC of Xinjiang 750kV power grid,which is of great significance to ensure the safe and stable operation of the Xinjiang power grid.