Study On Properties Of Carbon Fiber-Graphite Composite Grounding Material

In the power system,the key to lightning protection of transmission towers and power equipment is grounding.And the conductivity and stability of the grounding material play an important role in the lightning protection effect of the grounding system.The grounding material commonly used in the grounding system at this stage is still the traditional metal material.But the metal grounding material often corrode during application,resulting in a short service life and unstable grounding properties.In recent years,the graphite composite grounding material made of non-metallic material graphite has solved the corrosion problem of metal grounding materials in the soil environment.However,due to external force and environmental factors,the problem of outer graphite shedding occurs in the process of using the graphite composite grounding material as a grounding down lead,which seriously affects its grounding effect.In order to improve the performance of graphite composite grounding materials,this paper studies a new non-metallic grounding material made of carbon fiber and graphite,FGCF grounding material,to explore the influence of carbon fiber on the performance of the grounding down conductor,thereby further improving the actual service life of the grounding system.In this paper,a 2D finite element calculation model is established by COMSOL Multiphysics simulation software,and the skin effect,inductance effect and temperature characteristics of steel,copper,graphite composite grounding materials and FGCF grounding materials are studied.Among them,the conductivity and relative permeability of FGCF grounding materials are small.Therefore,the FGCF grounding material has less been affected by the skin effect and the inductance effect under the action of high-frequency current,and has stronger grounding dispersion ability and material utilization.Moreover,the dynamic thermal stability of FGCF grounding material is also better under the action of short-circuit current.Through COMSOL Multiphysics simulation software,a 3D finite element calculation model was established to study the impact resistance characteristics of steel,copper,graphite composite grounding materials and FGCF grounding materials under the action of lightning current.The Heidler function model,which is similar to the actual lightning current waveform,was selected as the lightning current model function.And the impact grounding resistance of four grounding materials under the action of lightning current was calculated.Among them,FGCF grounding material has the smallest impact grounding resistance,the best impact resistance performance,and the strongest ability to evacuate lightning current.Finally,the FGCF grounding material was prepared and studied for its physical and chemical properties,including mechanical property test,electrical property test and corrosion test.The test results show that the FGCF grounding material meets the technical requirements of the grounding body.By comparing the FGCF grounding material with the graphite composite grounding material,the FGCF grounding material has lower resistivity,more stable mechanical properties,as well as stronger impact resistance and high and low temperature tolerance.Compared with metal grounding materials,FGCF grounding materials and graphite composite grounding materials have stronger corrosion resistance.But among the two,the FGCF grounding material has a smaller rate of change in the ground resistance before and after corrosion and more stable grounding performance.