高土壤电阻率条件下变电所接地设计与实施

由于平地资源稀缺,220kV青田变所址选择在丘陵山顶上。所址区浅表覆盖层浅薄,下伏基岩为花岗岩,所址区的接地条件极差。根据土壤电阻率实测数据,所址处120m土壤电阻率的加权平均值为3809Ω.m,不采取措施的条件下接地电阻理论计算值超过10Ω。为了满足接触电位差、跨步电位差以及计算机监控系统的接地要求,采取措施使220kV青田变工频接地电阻目标值取降到1Ω以下,并满足国家电力行业标准对接地网的要求;为满足防雷接地的要求,采取措施使所区冲击接地电阻降到10Ω以下。采用设计—施工—反馈—设计的方法,使工程规模和费用得到有效控制。青田变的接地设计也为今后同类工程提供了经验。

Grounding Design and Appling of Transformer Substation High Soil Resistivity

Being short of flat ground,the 220kV Qintian substation site locates on the top of a hill which is near the northern bank of the Ou river.In the site the topsoil is thin and the underside is granite.So the electrical grounding condition is very bad.To meet the request of Chinese electrical power trade standards,the substation grounding system is expanded outside the substation to lower the power frequency grounding resistance below 1 which met the touch voltage and step voltage and the requests for the supervisory and control computer system grounding.The resistance of the substation internal grounding system is lowered below 10 to meet the request of lightning protection.We adopt the feedback method to control the construction cost and project scale.It will offer the engineering experiences to the similar project.