取消人工接地体在±800 kV哈郑直流工程中的适用范围分析

Applicable Scope Analysis of Independent Footing Grounding in ± 800 kV Hami-Zhengzhou DC Project

为提高±800 kV哈郑直流输电线路接地系统的技术经济性,在输电线路杆塔反击耐雷性能和人身安全分析的基础上,提出了取消人工接地体而采用基础独立接地所需的接地电阻与接触、跨步电位差的控制目标,对典型杆塔基础接地体的接地电阻和电位差进行了计算,获得了接地电阻和电位差与土壤电阻率的关系,据此提出了满足接地电阻和电位差目标的土壤电阻率范围。结果表明:不需要考虑接触和跨步电位差的野外地区,在西北少雷区,可采用基础独立接地的最大土壤电阻率可达1 700Ω·m以上,在非西北少雷区,最大土壤电阻率通常在1 000Ω·m以下。电位差对土壤电阻率的要求更严,需考虑电位差要求时,较小尺寸基础可独立接地的最大土壤电阻率通常在100Ω·m左右,更大尺寸基础可独立接地的最大土壤电阻率可达数百欧妙·米及以上。结合哈郑线的实际情况,选择了20基杆塔进行取消人工接地体的工程示范应用,其接地电阻和电位差均可满足技术和人身安全要求。

In order to improve the technical economy of tower grounding system for ± 800 kV Hami-Zhengzhou UHV DC transmission project,based on the analysis of back-striking lightning performance and personal safety around the transmission tower,control targets of the grounding resistance,the touch potential difference,and the step potential difference of independent footing grounding bodies while cancelling artificial grounding bodies are proposed,then the relationship between the grounding resistance,the potential difference and the soil resistivity are obtained under simulation calculation of typical tower footing grounding bodies,based on which the soil resistivity ranges satisfying the grounding resistance and potential difference targets are proposed. The results show that the maximum soil resistivity can be above1 700 Ω·m in the northwest less thunderstorm region,and the maximum soil resistivity is usually below1 000 Ω·m in the non-northwest less thunderstorm region without considering the touch and step potential difference. The potential difference is more strict to the soil resistivity,and the max suitable soil resistivity for independent footing grounding is around 100 Ω ·m for the smaller size foundation,and is several hundred Ω·m and above for the larger size foundation. Combined with the actual conditions,20 tower footings of the Hami-Zhengzhou transmission line are chosen for independent footing grounding demonstration application,and their grounding resistances and potential difference around the towers are checked,which can satisfy the technical and safety requirements.