Research On Calculation Method Of Geoelectric Field Induced By Geomagnetic Storm Based On Generalized Finite Difference Method

The solar storm will form a magnetospheric-ionospheric current system in the near earth space,which could cause severe disturbance of geomagnetic field and form"geomagnetic storm",and then generate geomagnetic induced current(GIC),which flows into power system through grounding point,endangering the safe operation of power grid.GIC has caused several blackouts in high latitude areas.The calculation of geomagnetic induced electric field under strong magnetic storm is the premise of accurately evaluating GIC level and preventing magnetic storm disaster.In this paper,the generalized finite difference method(GFDM)is introduced into the calculation of geomagnetic induced electric field under strong magnetic storm.The research contents and main results are as follows:(1)The basic principle of GFDM,the establishment of solution domain and support domain,the calculation process and the method of time domain discretization are studied.According to the generation process of GIC,the different forms of space current source and different models of earth conductivity are summarized and introduced,and the forms of geomagnetic disturbance data in each stage are analyzed.Finally,the mathematical model of geomagnetic storm induced geoelectric field is given.This part provides theoretical support for the following theoretical derivation,example verification and engineering example calculation.(2)The discrete schemes of the control equations and boundary conditions of the geomagnetic storm induced geoelectric field in the space domain and time domain are derived.The Crank-Nicolson Implicit Scheme is used for the time domain discretization.The GFDM domain form of the geomagnetic storm induced geoelectric field is derived according to the domain decomposition method.The above two parts are verified by numerical examples and analyzed by parameters.The results show that GFDM has good accuracy and stability,and the total number of points in the solution domain has more influence on the accuracy than the number of points in the support domain.(3)In this paper,the results of plane-wave and GFDM are compared.The results show that when there is no lateral geological mutation,the two results are consistent.However,the plane wave method can not reflect the two polarization effects of induced geoelectric field at the interface when there are transverse geological differences,and the error is too large.After the spatial domain of GFDM is discretized,the calculation process of each direction is independent,which can better deal with the lateral geological differences..(4)A three-dimensional field model of coastal area is established.According to the geological exploration results of Guangdong area and combined with the geomagnetic disturbance data of geomagnetic station,the coastal area near Lingao nuclear power station is calculated to explore the influence of coastal effect.The time-varying results of electric field intensity and potential difference of Dongguan,Shenzhen substations and Lingao nuclear power station are obtained.The results show that the electric field intensity and potential difference in the high resistance area where Jieyang measuring point is located are relatively low The field intensity exceeds $V/km and decays to inland area.The 1 V/km uniform field intensity commonly used in GIC calculation is no longer applicable.The maximum potential difference between Dongguan station and Ling'ao station can reach 120V during the magnetic storm.Compared with the measured data of GIC,it is found that the variation trend of the two stations is consistent,and the maximum value appears at the same time.GFDM is introduced into the calculation of induced earth electric field under strong magnetic storm for the first time,and its accuracy and stability are verified.The calculation of engineering example is carried out,and the results are reliable.It provides a new way for the calculation of induced earth electric field under strong magnetic storm,which is of great significance to prevent and control the geomagnetic storm disaster.