Research On Change Rules And Influencing Factors Of Grounding Grid’s Diverting Potential In Substation

Grounding technology has profound influence on the safe and reliable operation of power system. With the expansion of generator capacity, the promotion of HVDC transmission system, the growing grounding current, these developments have provide the reliability, safety and effeciency of substation operation with more changllenges. In practical projects, when substation is located on granite or other areas where the soil are a high resistivity and shortcircuit current is much too large, it’s so difficult and expensive to establish a huge grounding device which has low resistivity.Therefore, in the condition of large substation capacity and high soil resistivity, it’s impossible to make grounding resistance low.When short-circuit fault happens in the substation, the potential in the substation or around will rise considerably because of great current fed to grounding grids. The potential will be obtained by secondary equipments grounded, which is referred to diverting potential. Diverting potential may destroy the insulation of secondary equipments, especially communication cables or other lines, causing personnel accident in the substation.Firstly, aiming at question of grounding grids, the thesis summaries the reaserch on how to reduce the grounding resistance and balance the potential in the grounding grids and optimization measures.And then, the transmission properties of diverting petential in the substation are anlyzed with an numerical calculation method of substation grounding grids with unequal-potential, analysis formula of calbe’s diverting potential is obtained. Using grounding grids simulation software—CDEGS, change rules and influencing factors of diverting potential are discused on the condition that cable core is connected with grounding grids. The simulation results is largely consistent with the trend calculated by the formula. Finally, through the design of Kangting500kV substation grouding system, the design method is introduced. The optimal program is discused through repeated calculation using CDEGS. Measures which restrain adverting potential in the substation are introduced, providing theoretical basis on engineering design of substation grounding system.