考虑地表高阻层的直流接地极跨步电压限值计算方法

Research on Calculation Method for Step Voltage Limitation of DC Grounding Electrode Based on Surface High-Resistance Covering

为保证直流接地极附近人身安全,接地设计时必须满足跨步电压限值要求。针对水平双圆环形直流接地极,考虑在接地极上方地表铺设高阻层,研究在此条件下跨步电压限值的计算方法,并给出了新计算公式,最后基于边界元法对不同土壤条件下的直流接地参数进行研究分析。研究结果表明:直流接地极地表铺设高阻层能够有效提高人体耐受的跨步电压限值,建议铺设厚度为0.1~0.2 m;为明显提高跨步电压限值,选取的高阻层电阻率最好大于1 000Ω·m。研究结果还表明,铺设高阻层对直流接地极的接地电阻、地电位升、地面跨步电压以及泄漏电流的分布影响很小,对金属设施的影响也基本可以忽略。

In order to guarantee the human safety near the DC grounding electrode, the requirement of step voltage limit must be satisfied in grounding design. Based on the horizontal double-ring DC grounding electrode, the computation method of step voltage limit is studied under the condition of covering the ground surface of grounding electrode with high-resistance layer, and a new computational formula is given. And then the grounding characteristics under different soil conditions is analyzed by using the boundary element method. The investigation results show that the surface high-resistance covering can greatly improve the tolerance limit of the step voltage for human body. The thickness of high-resistance layer is suggested to be 10-20 cm. In order to substantially improve the tolerance limit, the resistivity of high-resistance covering is better to be greater than 1 000 Ω·m. It is also shown that tile surface high-resistance covering has little influences on the grounding resistance, ground potential rise, step voltage and distribution of leakage current, and its influence on the metallic facilities can also be neglected.