Selection Of Resistance Reducing Schemes And Grounding Materials In Substation Grounding System

With the expansion of power system capacity, the grounding short-circuit current is larger, in order to guarantee its safe and reliable operation, the requirements for the grounding system of its substation are much stricter. Recent years with the rapid improvement of equipments manufacture level and the restriction of substation site by planning, more Gas Insulated Switchgears are widely applied. All these induced the arrangement of substation changed more compacter and the floor space are only 25%～40% of the Air Insulated Switchgear and the secondary transformation of grounding screen are also more complex.Investigation shows many grounding screen corrosion were accrued in China due to the grounding resistance cannot meet the corresponding requirement. These accidents not only caused huge economic loss, but also caused more severe indirect economic loss to the whole society. According to the statistic, the loss caused by the grounding system accidents can reach millions and even ten millions each time, and the indirect economic loss are much heavier. Therefore it is important to ensure the grounding screen in every substation reach the safety index.The research status in China and abroad and the development of grounding technique are introduced at first. Secondly, the application of different grounding materials such as galvanized flat steel, pure copper, copperized steel are especially analyzed from the electric conductivity, thermal stability, anticorrosion and connection type by the comprehensive analysis and comparison of stability, life and economy. And the different grounding materials selected for different substation are acquired through practical projects. At the same time, the familiar resistance reduction measures for substation such as enlarging grounding screen area, grounding to outside, grounding to artesian well, using natural grounding body, using resistance reducer and local earth replacement are analyzed from the resistance reduction mechanism itself. Based on the soil difference among different substation sites, the resistance reduction method for the substation which located with higher soil resistivity is obtained by calculating and analyzing different resistance reduction measures.