Study On The Current Dispersing Characteristics Of Transmission Line Tower Typical Grounding Material

The grounding performance of transmission line tower grounding device has an important influence on the safe and stable operation of power system.The power system is developing towards larger scale?higher power and more intelligent direction,soreliable and safe operation of grounding system faces new challenges presented by transient fault currentcaused by fault,operation and lightning etc.Soil conditionas well as the skin effect and inductance effect of the grounding conductor in the role of high frequency current are important factors affecting the current dispersing characteristics of grounding device.The study of the influence of them on the current dispersing characteristics of the grounding body is of great significance to improve the lightning protection performance of the transmission line tower grounding system.In this paper,steel,manganese and graphite composite ground material grounding body under different frequency current is modeled and simulated in finite element simulation software Ansoft Maxwell.The skin effect and inductance effect of three kinds of grounding materials are analyzed and compared,through which it's showed that with the increase of the current frequency,the skin effect and inductance effect of the grounding body are more obvious,and the grounding material with relatively high permeability are more obvious.The difference between transient grounding resistance(TGR)under lightning current and grounding resistance under power current of grounding body with different materials is studied.The influence of skin effect and inductance on the current dispersing characteristics of the grounding device is studied as well.Through grounding calculation software CDEGS modeling and simulating ground body with three different materials in different soils,the law of dispersing current density of grounding body sections changing with soil resistivity and current frequency,which is that the larger the soil resistivity,the better the equilibrium of the grounding body current dispersing,the higher the frequency of current flowing into grounding body,and the more concentrated on injection point the grounding body dispersing current.And it's proved that the change of upper layer soil resistivity of two-layer soil plays a leading role in current dispersing characteristics of the grounding body.Through grounding calculation software CDEGS modeling and simulating the grounding grids composed of three kinds of grounding materials,the law of the soil resistivity,the diameter of the grounding body and the current frequency affect the grounding impedance of grounding grid is obtained.It's proved by an example that graphite composite grounding material can effectively prevent the corrosion of grounding body under extreme soil conditions,and grounding impedance of the grounding grids of tower meet the standards,the grounding material has application value and prospect in practical projects.