Distribution Characteristics Of Geomagnetically Induced Current In Power Network And Identification Of Weak Links

Dramatic changes in the earth’s magnetic field caused by solar activity are called geomagnetic storms.In extreme space weather,geomagnetically induced current(GIC)is driven by an electric field induced by the surface of the Earth’s magnetic field.Typically,GIC can flow into the transformers through the neutral point because the transformers are directly grounded.Once the amplitude of GIC exceeds the allowable limit of the system,it will lead to transformer semi-periodic saturation and a large number of harmonics generation,which will threaten the safe operation of the whole power systemFirstly,based on the plane wave theory,a uniform earth model is established based on the measured geomagnetic components at the Finnish station.The induced geoelectric field calculation formula is discretized to solve GIC in power network.The calculated value is compared with the measured GIC.On this basis,the DC modeling of each part of the power network is carried out.GIC-Benchmark model is selected as a typical example to analyze GIC flow in each node and transmission line of its full node model under two special and uniform ground electric fieldsSecondly,considering the current research status of Shandong power grid in GIC,the GIC calculation model of 34 substation nodes and 46 transmission lines in Shandong 500kV power grid is established.Firstly,the GIC level in two special induced geoelectric fields is calculated,and the distribution characteristics and rules of GIC in substations and transmission lines in the power grid are analyzed Based on the variation characteristics of GIC field direction,the GIC magnitude of 34 substations under all geoelectric field angles from 0° to 360° was calculated The maximum GIC value of each substation in a certain direction is calculated.On this basis,a method to identify the weakest link in the power grid.The key substation is proposed in combination with the principle of statistics,and the relative vulnerability degree of each substation is calculated.Finally,with the help of ArcGIS platform,the spatial distribution of GIC weak areas was analyzed from the prediction point to the prediction surface.Finally,considering the functions of different grid components in the GIC calculation model,the influence of different resistance parameters on GIC was analyzed.When the change of transmission line resistance is found,GIC in the substation and transmission line fluctuates most violently.Taking transmission lines as the research object,the influence effect of adding series compensation device on GIC is explored,and the principle of increasing reactive power of transformer is considered.Seven configuration schemes are assumed,and four effect evaluation indexes are proposed to analyze the effects of different schemes on GIC of substations.Then,the changes of GIC in the power grid before and after the addition of mitigation devices on long transmission lines are explored from the distribution changes of GIC in each substation,the changes of reactive power loss and the transfer of key substations.In this paper,the influence process of geomagnetic storm disaster on power grid is studied in detail.The research method provides useful reference for GIC characteristic analysis,weak link identification,vulnerability assessment,GIC inhibition optimization,monitoring equipment installation.