Study On Lightning Performance For Graphite Ground Device Of The Transmission Tower

Lightning is the majority cause of line faults.The grounding is the base of preventing lightning accidents.The grounding device of the transmission line tower plays an important role in preventing the lightning disturbance.Steel is mainly used for the ground device of the transmission tower.Steel is easily corroded and rusted with high damage rate,high renewal expenses,and pollution to the environment.With the corrosion of the grounding device,grounding resistance increases and lightening accidents may occur.Therefore,reducing the grounding resistance is an important measure to prevent corrosion.Graphite has good electrical conductivity and strong corrosion resistance.Therefore,this paper will discuss the graphite used for the grounding device and analyze the lightning protection performance of the transmission tower with graphite grounding device.First this paper summarizes the development and application of the transmission line tower grounding device,the principle of lightning protection and the lightning protection measures.With the help of software CDEGS,grounding device models will be conducted.The ground impedance of three materials graphite,steel and copper will be compared and analyzed relatively under the conditions of different soil resistivity,different size of grounding devices and different frequency current.The conclusion is that the resistance of the graphite grounding device decreases.Meanwhile,this paper sets up the model of the 220kV transmission line tower and its grounding device based on frequency domain method and the impulse characteristics of the grounding device of the three materials under the lightning stroke will be analyzed.As back striking is closely related to earthing resistance,this paper established the lightning protection level calculation model of back striking including the tower,the lines,insulation arc-over and grounding resistance.Then the lightning protection level of the graphite grounding device will be compared with the lightning protection level of the steel grounding device.