评价交流接地网施工及运行可靠性的相关问题分析

结合现场测试情况以及解决部分接地施工验收争议问题的经验,提出接地网评价的主要指标,如:电气完整性测试结果、接地电阻校核、接触及跨步电压校核、接地网导体通流容量验算、所处土壤的电阻率及pH值。以上指标均能定量,易于形成评价分值。对新建投运与运行多年两类情况,各指标所占权重应有差异。在运行中的发、变电站内,采用变频电流注入,可降低测试接触及跨步电压的不确定度。因土壤电阻率与入地电流频率间有关系,采用变频不宜偏离工频超过10Hz。在不同温、湿度条件下测量,接地网电阻有一定差异,这种差异有时会达到25%。

Relevant Aspects Concerning Grounding Grid of A.C.Grounding Grid Construction Work and Service Reliability

Based on site measurements and dispute solutions at grounding project take-over,main parameter at evaluation of grounding grid,such as measurement result of electrical integrity,grounding resistance examination,contact and step voltage examination,examination of discharge capacity of grounding conductor,soil resistivity and pH value.All three parameter are quantitative for easy classification.The parameter weighting shall be different for grids newly elected and operated for many years.At running stations and substations introduction of converted current may reduce the uncertainty of contact and step voltage measurement.The frequency converting shall be not be deviated from power frequency be more than 10Hz since the soil resistivity is correlated with current frequency.Deviation of measured resistance may reach 25% as measured at temperature and humidity.