| The economic development has greatly promoted China's demand for electricity consumption.In the meanwhile,the surge in power transmission and transformation projects has also led to tensions in transmission corridors.Complex terrain and soil conditions have increased technical and construction difficulties.If the grounding parameters such as grounding resistance cannot meet the safety requirements,the safety of the grounding project would be reduced,resulting in a safety accident and causing huge losses to the country.Therefore,in order to ensure the reliability and stability of the grounding engineering,it is necessary to study the grounding resistance of the grounding grid,making improvements for the grounding resistance reduction methods,helping solve problems in this field,and thus the earthing effect can be guarenteed under the premises of safety and stable operation of the tranmission and transformation projects,as well as easing the construction dfficulties and cost.The grounding system must at least meet the service life and economic requirements under the premise of ensuring the grounding effect.However,in the past,most of the researches on the high soil resistivity grounding system are difficult to better meet the requirements of these two aspects.Chemical methods such as the relatively low-cost resistive agent method dose work effectively,but the duration of the effect is often greatly discounted.Besides,the corrosion rate of the grounded metal is also intensified;Physical methods,such as blasting grounding and deep well grounding,etc.,requires a lot about terrain conditions in the construction area,and their cost as well as constructing difficulty is also relatively high.So,there is a need for a new material or method to improve the grounding effect of the tranmission tower in high-resistance area balancing the economy and durability in grounding engineerings.Although many different types of composite materials have been applied to power system,There are few studies on the application of cement-based composite materials on improving the grounding effect of tranmission towers in high resistance areas.The main research results of this thesis are as follows:(1)The grounding model of the transmission tower and the application model of the cement-based composite grounding material are established.According to the construction standard,the CDEGS simulation software was used to build a transmission tower grounding grid model for the soil resistivity in the range of 100-4000 ?·m.Basing on the resistance reduction principal,the simulation possibbilities of soil block in the simulation module are analyzed,and two composite application models of partial-wrapping and full-laying are proposed.Then,the effect of reducing the resistance of cement-based composite grounding materials was verified in mudule MALZ and a method of reducing the resistance of partial and horizontal emitters was proposed.Considering from the two aspects of resistance-reducing and groundpotential improvement,selecting a suitable composite material applying model.And then experiments about the proposed combined resistance-reducing method were carried out in the purpose of studying its application range.(2)The testing samples were prepared and the anti-corrosion tests of the cement-based compositing grounding material were carried out to verify its corrosion resistance.First,cement,fine sand,graphite,stainless steel fiber,zinc-clad steel and Q235 carbon steel were used to prepare the testing samples.Then,the testing samples were tested from two aspects of electrical properties and mechanical properties.After being qualified,open circuit potential,dynamic potential polarization and electrochemical impedance spectroscopy were tested according to the electrochemical corrosion testing plan,studying the corrosion of the grounded metal in the cement-based composited-grounding material. |
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