Research On Reducing Resistance Of The New-type SAP Ground Composite

With the rapid development of the economy,the radiation area of the power transmission corridor is becoming wider and wider.Overhead lines will go through more remote areas where the geological environment is more complex.These areas tend to have high soil resistivity,which poses great challenges for tower grounding projects,especially in the rocky and water deficient area where soil gravel,sand and gravel content is much.At present,common resistance reducing materials are used to reduce grounding resistance.and the resistance materials used in the market are all strong hygroscopicity,because the soil moisture is very important for the flow of lightning current in the earth.SAP is a new kind of functional polymer material.The most outstanding performance characteristics are super absorbent and high water holding capacity.It also has a series of high quality characteristics such as repeated use,good safety performance,low corrosion and so on.In order to apply SAP’s high water absorption and water retention property to the grounding project,a new type of SAP grounding composite material with low resistivity and long moisture retention is developed based on SAP in this paper.The electrical properties of SAP are modified by adding conductive particles.The results show that the particle size,density,chemical activity and dispersion in SAP are very important to the resistivity of the resistance reduction material.Graphite,carbon black and carbon fiber used as conductive filler in the project can effectively reduce the SAP resistivity,and the effect is better than that of metal conductive particle iron(Fe),nickel(Ni)and copper(Cu).The optimum mass fraction of the new SAP ground composite material is SAP 42%,graphite 12%,carbon black 3%,carbon fiber 3%,conductive cement 40%,and the resistivity can be as low as 1.42 Ω·m based on the orthogonal experimental method.The simulation experiment of lightning current impact tolerance further tests the feasibility of the new material application.The instantaneous high temperature of the lightning current accelerates the heat movement of water molecules,which causes the water molecules to break off the binding of the SAP threedimensional cross-linking network,but the resistivity change rate of the new SAP ground composite material is less than 20% before and after the experiment,which meets the requirements of the industry standard.Finally,the influence of the thickness,laying position and resistivity fluctuation of the resistance reduction material on reducing the grounding resistance in different soil resistivity is studied by the linear three pole field measurement and the electromagnetic analysis software CDEGS.It provides some reference for the site construction of the resistance reduction material.