变电站接地极换土法的接地降阻效率研究

Research on the Earthing Resistance Reduction Efficiency of the Substation Earthing Electrode Soil Exchange Method

通过对接地极换土法接地电阻的精确计算,对接地极换土法的接地降阻效率进行了研究。依据复合接地网接地电阻的计算方法,提出了换土后接地网接地电阻的一种接地极等效直径变换计算法,基于该方法,从置换土的土壤电阻率和换土半径两方面对换土后的降阻效率进行了研究。研究表明,置换土土壤电阻率越低,换土半径越大,接地电阻降低越明显,但降低并不成比例。换土法等效于增加了接地极直径,理想情况下其接地降阻效率仅接近5%,降阻效率并不明显,故在变电站接地网接地电阻值不满足安全要求时不建议专门采用该降阻措施。当现场有足够的低电阻率土壤时,推荐采用低电阻率土壤回填,当无足够的低电阻率土壤时,应优先考虑采用降阻剂或离子接地极等其他接地降阻措施。

The earthing resistance reduction efficiency of the earthing electrode soil replacement method is indepth research Through the accurate calculation of grounding resistance.an equivalent transformation calcula⁃tion method of the earthing resistance after soil replacement was proposed according to calculation method of earthing resistance of composite grounding grid.Based on this method,the resistance reduction efficiency of soil was studied.Studies have shown that,the lower the soil resistivity of the replacement soil and the larger the replacement radius,the more obvious the decrease in ground resistance,but this relationship is not in propor⁃tion.The essence of the soil replacement method is to artificially increase the equivalent radius of the earthing electrode.Ideally,the earthing resistance reduction efficiency is only close to 5%,meanwhile the resistance re⁃duction efficiency is not obvious.Therefore,it is not recommended to use this resistance reduction method when the earthing resistance of the substation does not meet the safe value.When there is enough low-resistivity soil on site,try to use low-resistivity soil for back filling.