Simulation And Study On The Distribution Characteristics Of Current In Soil During The Transmission Tower Being Lightning Struck

When the lightning strikes the transmission tower,the lightning current is very large,so that the current density in the earth flow is very large and accompanied by varying degrees of soil breakdown process.Many power transmission tower grounding system can meet the overall requirements of grounding resistance,but in the design of lacking of specialized and systematic research.The lightning current flow into the irregularly channeling ground and surface,seriously affecting the safety of the surrounding biological.The For example,in recent years,the Pearl River Delta region has even been hazardous to biosecurity accidents,such as the transmission line tower near the fish pond after the thunderstorms,fish ponds in the phenomenon of a large number of fish have died.There have been many in the jurisdiction of Foshan Power Supply Bureau,resulting in local power supply and local farmers between the more disputes.In order to solve this problem,it is urgent to establish the relevant design and reconstruction guidance through site investigation and simulation research,and put forward the corresponding protective measures.In this paper,COMSOL Multiphysics finite element software is used to simulate the simulation.In order to establish the simulation model of the ground leakage current in the field,the lightning current waveform and the energy distribution are analyzed.Based on the theoretical analysis of the lightning current flowing process,the mathematic model describing the physical process is established step by step.According to the physical constraints,the model boundary condition is set up,combined with the site survey and analysis of the transmission line tower grounding system,the underground environment and the surrounding lightning current distribution.The ground impedance of KR-1G grounding device at each frequency is compared with the simulation result of internationally recognized grounding software CDEGS.The results are basically the same.It can be concluded that the simulation model can approximate the current in the frequency domain.According to the simulation results,it is shown that with the increase of soil resistivity,the current density and the current density of the fish will continue to rise,but the rising trend will be slow.The structure of the grounding device will affect the size of the current density in the ground.The distance between the grounding device and the fish pond increases,the current density in the fish pond is getting smaller and smaller,and there is a certain safety distance,but the safe distance in the higher soil resistivity will increase.The fish in the bottom of the fish pond are less affected by the fish that live on the surface of the fish pond.In the same lightning strike tower accident,the fish less affected by the change of the fish ponds and can be neglected.According to the simulation results:when the accident site of soil conditions are low,through the grounding device insulation shield,and add the reverse extension of the horizontal grounding;or through the flat copper core insulation lead outside the grounding device.Increases the distance between the grounding device and the fish pond,will be able to avoid accidents.When there is a certain distance between the tower and the fish pond,it is feasible to install the insulation board between the grounding device and the fish pond to block the path of the lightning flow to the fish pond.