Research On Optimal Placement For GIC Mitigation With Blocking Device

With the development of the national economy,the power grid continues to develop toward high voltage,long distance and large capacity,the geomagnetically induced current(GIC)caused by geomagnetic storms will increase the risk of damage to the power grid.The existing DC blocking device placement strategy is to install capacitor blocking device preferentially at a substation with a large GIC to mitigate the impact of the geomagnetic storm,but this may increase the GIC of the installation station adjacent to the substation.It is of of great significance for GIC mitigation and the safety,stability and economic operation of power system to optimize the placement of capacitor blocking device.The main research contents and results of this paper are as follows:Firstly,according to the flow characteristics of GIC in the grounding grid,combined with the construction of the grid component model,the node admittance calculation method of the grid GIC is derived,the effective bias current of the transformer is used to represent the DC bias of the autotransformer.Based on the grid component parameters,the GIC distribution of Xinjiang planning grid under the influence of different amplitude uniform electric fields is calculated.The results show that the GIC of the transmission line is larger when the direction of the electric field is close to that of the grid transmission line.Secondly,the GIC suppression effect of the traditional capacitor blocking device placement on the planned grid in Xinjiang in 2020 is calculated and analyzed.The results show that with the installation of the blocking device,the GIC of other substations passively exceeds the limit in the power grid.Under the influence of the electric field of 0.5V/km,considering the change of the electric field direction,in order to reduce the substation GIC to the allowable limits,the number of installed blocking devices is up to 40.Then,in order to overcome the limitations of the traditional placement strategy,the placement of the capacitor blocking device is optimized based on the multi-population genetic algorithm,and the optimal placement of the capacitor blocking device under the influence of different electric field amplitudes is analyzed and compared.The results show that under the condition that all GICs in the substation are less than the allowable limit,the number of blocking devices required for the optimal placement is less than the traditional placement.Finally,the influence law of the GIC of the Xinjiang planning grid is changed by the local and adjacent substation grounding resistance is calculated and analyzed.Combined with the sensitivity analysis of the GIC to the grounding resistance,a hybrid optimal placement of the DC blocking device and the resistor is proposed.The optimized configuration result of the hybrid optimized placement shows that under the same constraints,the hybrid optimized configuration scheme requires fewer capacitor blocking devices than the blocking device optimal placement.The optimal configuration strategy of grid GIC mitigation discussed in this paper has certain guiding significance for the scientific mitigation of grid GIC.