Study On Performance Of Grounding Grid With Slanting Electrode

To design a substation grounding grid reasonable has a very important significanceto the power system. It makes the power system stable and safe. The substationgrounding grid in power system can quickly discharge the fault current into the ground.Thus the touch voltage and the step voltage and maximum voltage potential rise couldstay below the safety limits. At the same time it can also ensure the safe of thesubstation operators and the equipments.In the last few years, domestic new substation projects are mostly builded in thehigh resistivity areas. Due to many factors, such as the difficulty of the land acquisition.Many substations had to cover a small area, especially the gas insulated substation.Some experts and scholars present a new method which called the slanting electrodes.This method can improve the performance of grounding grid in poor geographicalconditions. The slanting grounding electrodes can not only play the role of the verticalgrounding electrodes, but also play a role of expanding area equivalent. The shieldingfactor of slanting electrodes is smaller than the vertical grounding electrodes. So theutilization factor of the slanting grounding electrode is higher than the verticalgrounding electrode.This paper, based on CDEGS grounding engineering calculation software whichdeveloped by Canadian SES company. The3D simulation model of the slantinggrounding electrodes in the square and the rectangular grounding grids were established.The optimal arrangement of the single slanting grounding electrodes in different shapesof grounding grids was analyzed. The result is to decorate the slanting groundingelectrodes in the corners or in the edge of the grounding grid could get the bestresistance reduction effect. The slanting electrodes and the vertical direction’s includedangle θ is60°. It can get the best resistance reduction effect when the slanting electrodesfix up in the corners of the grounding grid. The study of the optimal layout rules and theeffect of balancing voltage in uniform soil with different area of square and rectangleand different length of the slanting electrodes and different roots of the slantingelectrodes were analysed. The result is that applying slanting electrodes to the area in100×100(m2) is better. The study based on these conclusions which considered of theslanting electrodes comprehensive from the aspect of technical-economy. The different injecting point of short-circuit current into the influence of the grounding grid voltagewere analyzed.The distribution of soil resistivity is usually uneven along the depth and transversein practical engineering. It’s hard to meet the uniform soil structure. To use the longvertical grounding electrodes or deep well grounding connected with the maingrounding grid is a kind of effective method of reducing grounding resistance in thehigh resistivity area and some regions which can’t use the conventional method to burygrounding devices. The slanting electrodes as a new resistance reduction it is necessaryto make a comparison with the vertical grounding on the effect of performance ofgrounding grid. In this paper, it had made a comparison with effect of resistancereduction by using the vertical electrode or the slanting electrode in the different soilstructure. The study found that the resistance reduction effect of the slanting electrodesis better than the resistance reduction effect of the vertical electrodes with the samelength in uniform soil structure. The resistance reduction effect of two kinds ofelectrodes depend the actual soil structure in the layered soil. It should be taken intoaccount various factors when select method of resistance reducing. It is the same trendresistance reduction effect and the balancing voltages of two kinds of groundingelectrodes. This paper also analyzed each segment’s leakage current of the slantingelectrodes and the vertical electrodes, and also analyzed the influence of the thicknessof upper soil to resistance reduction effect.Combined with the above research and according to the specific conditions of theoriginal substation grounding grids two110kV in Zhou Kou substation. It was achievethe project safety requirements by using the slanting electrodes.