| Power system operation experience has shown that,the reliable operation of the grounding device is of great significance to ensure the safe and reliable operation of the power system and ensure the safety of the electrical equipment and the operation personnel.The reliability of the grounding device directly affects the lightning protection effect of the power system equipment.The existing grounding device is widely made of steel,copper metal material,while the metal grounding material is facing the corrosion problem in the actual operation,threatening the safe operation of the power grid.In order to solve the problem of corrosion of steel metal mesh,many researchers at home and abroad have shifted their attention to nonmetallic grounding materials.The flexible graphite composite grounding device,which are made of graphite as the main raw material,has more advantages than the traditional steel grounding material in the construction of easy,anti-theft performance,anti-corrosion performance,and it can fundamentally solve the problem of grounding grid corrosion.In order to illustrate the advantages of flexible graphite composite grounding device relative to the existing steel grounding material,this paper uses the simulation and test methods to compare the differences between the flexible graphite composite grounding device and existing steel grounding material grounding material based on the analysis of the theory,test and engineering application.This paper will provide support for the use of flexible graphite composite grounding device in the actual engineer project.The main work of this paper is as follows:(1)The differences in skin effect of the manganin,round steel and lexible graphite composite grounding device are compared and analyzed by using the finite element calculation method.The influence of skin effect and inductance e:ffect on grounding resistance is analyzed theoretically,which provides a theoretical reference for the optimization of the flexible graphite composite grounding device.On the basis of the above research,the cross section structure of graphite based flexible grounding device are improved in order to further reduce the influence of skin effect and improve the utilization ratio of graphite conductive material.(2)The current distribution characteristics of several grounding materials under different circumstances,for example,manganin,round steel and flexible graphite composite grounding device,are compared and analyzed.CDEGS software is used to establish the simulation model to calculate the current distribution characteristics of different grounding materials,the current distribution differences between the flexible graphite composite grounding device and the traditional metal grounding materials are analyzed under different soil resistivity,entering grounding current frequency and different grounding electrode diameter.(3)The impulse grounding resistance equivalent diameter iterative computation method is discussed with the considering of spark effect,and the results are compared with the experimental data reported in literatures.A single horizontal flexible graphite composite grounding device and transmission line tower grounding grid with short grounding rod grounding characteristics are simulated with CDEGS software,the influence of short conductor on the horizontal grounding body and tower grounding grid impulse grounding resistance are analyzed.(4)Based on the results of theoretical simulation,the experimental model of flexible graphite composite grounding device and round steel are established,and the impact grounding test is carried out.The current distribution characteristics of 10mm diameter round steel and 28mm diameter flexible graphite composite grounding device are compared,which provide valuable scientific measurement data for the popularization and application of flexible graphite composite grounding device. |
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