Study On Geomagnetically Induced Current And Its Influence On Power System

The solar activity will cause the geomagnetic storm and the disturbance of earth space current system,which in turn induces electric fields on the earth surface,thus generating geomagnetically induced current(GIC).GIC will result in transformer half-wave saturation,harmonics and reactive power increase.This will cause insufficient reactive power and voltage fluctuation in the system,and even cause voltage collapse,endangering the safe operation of the power grid.This thesis mainly studies GIC with different voltage levels and its influence on power system.First,based on the quasi-DC characteristics of GIC,DC model of the power grid is built,and the simulation method of GIC by PowerWorld Simulation(PWS)and the node voltage method are introduced.On this basis,five UHV substations located in Shandong are taken as the research objects and PWS is used for simulation.In addition,taking 1000 kV substations and 500 kV substations in Shandong as research objects,under the scene of uniform ground electric field,the GIC level of each substation is evaluated and analyzed to clarify the substations that the GIC are large or even beyond the limit.Secondly,considering the types of transformers with different voltage levels,the reactive power losses of UHV and UHV substations under different ground electric field scenarios are quantitatively analyzed.Based on the results of GIC,according to the characteristic that GIC is approximately linear with the increment of reactive power loss,the increment of reactive power loss of 500 kV UHV Transformer in Shandong is calculated by K value method,and the increment of reactive power loss of 1000 kV UHV Transformer is calculated by U-I curve method.The relationship between GIC and reactive power loss of UHV Transformer is fitted,and the substation with large reactive power demand and the sensitive direction of ground electric field are identified.Finally,considering the influence of reactive power variation on system voltage,the power flow analysis method and the voltage fluctuation model of long-distance transmission line under geomagnetic storm are established to analyze the node voltage fluctuation caused by GIC.In addition,the voltage out of limit index is defined to evaluate the voltage out of limit state of system nodes.Taking the dual machine six-bus system and IEEE standard 39-bus test system as examples,the voltage fluctuation and out of limit index of the nodes are analyzed under different geoelectric field scenarios,and the sensitive geoelectric field direction is identified according to the voltage out of limit index.This thesis provides a theoretical basis for the study of GIC and its impact on power grid.The above methods can be extended to systems with different network structures.It is of great significance to evaluate the impact of geomagnetic storms on large-scale systems.