Induced Ceoelectric Field Calculation And Distribution Characteristics Analysis Based On Geomagnetic Data

With the construction of 1000 kV UHV transmission lines in China,the risk of GIC impact on the power grid will be greatly increased.GIC poses a serious threat to the safe operation of power grid and power grid equipment,including misoperation of relay protection devices,overload of capacitor banks and static var compensation devices,filter overload at AC side at the end of HVDC converter station,system voltage fluctuation,etc.Therefore,it is of great significance to study the impact of magnetic storms on power grid,ensure the safe operation of power grid,and accurately calculate and analyze the distribution law of induced geoelectric field.In this thesis,the shape and characteristics of geomagnetism are summarized,and several important factors affecting induced geoelectric field and GIC are analyzed.The key to accurately calculate the impact of magnetic storms on power grid is to calculate the distribution of induced geoelectric field.Because of the strong correlation between GIC and the time-varying rate of geomagnetic field horizontal component(dH/dt),in order to accurately calculate and analyze the distribution law of induced geoelectric field,a time-harmonic fitting algorithm is proposed to transform the time-varying geomagnetic field into the frequency-domain phasor method.The time-harmonic fitting of the magnetic storm data in 2004 is selected,and the one-dimensional stratified conductivity model of Laxiwa,Northwest China,is used to carry out the time-harmonic fitting.Comparing the results of time domain calculation and frequency domain calculation,it is proved that the accuracy of the algorithm is higher,and the calculation of induced geoelectric field is simplified,which lays a foundation for discussing the distribution law of geoelectric field.Based on the observed second data of several geomagnetic stations during the two magnetic storms in 2004 and 06,several pulses with fast time-varying horizontal component of geomagnetic field are selected for time-harmonic fitting,and the distribution law of amplitude B and frequency_of geomagnetic field change rate after time-harmonic fitting is analyzed.The distribution of induced geoelectric field in North China,East China,Central China,South China and Northwest China is calculated by using one-dimensional stratified conductivity data.It is found that the distribution of induced geoelectric field is very uneven.Compared with other regions,the value of induced geoelectric field in North China and South China is larger,while that in Northwest Xinjiang is smaller.Previous calculation of the neutral GIC of UHV transmission lines and substations is based on the uniform inductive geoelectric field calculation.The actual geoelectric field distribution is not uniform.The GIC level of UHV grid is calculated by the distribution of the induced geoelectric field calculated in this thesis.It is found that the GIC value of the neutral point of Beijing and Jindongnan substations is larger than that of other substations,and is more seriously affected by magnetic storms.