土壤介电频变特性对接地极冲击散流的影响

Influence of Soil Dielectric Constantês Frequency-dependent Characteristics on Impact Current Dispersal of Grounding Electrode

为研究土壤介电常数频变特性对接地极暂态电阻的影响规律,在典型土壤介电谱测量结果的基础上,对冲击电流作用下的动态电磁过程进行了理论分析。提出了从电磁场角度出发的、考虑土壤频变特性的接地极冲击特性数值计算方法,分析了土壤介电常数的频变特性对接地装置冲击散流特性的影响。结果表明:考虑土壤介电常数频变特性的接地极暂态接地电阻与假定介电常数恒定时相比有显著差异;暂态电阻值受到施加的冲击电流波形和幅值的影响,波前时间越长,局部峰值越大;同种冲击波形下,电流幅值越大,波前时间内接地极暂态接地电阻局部峰值越小。

In order to determine the relation between frequency-dependent characteristics of soil dielectric constant and transient grounding resistance, we measured the dielectric spectrum of typical soil, and analyzed the dynamic electro- magnetic process affected by impulse current theoretically. From the perspective of electromagnetic field, taking the frequency-dependent characteristics into consideration, we put forward a numerical calculation of impulse characteristics of the grounding electrode, and hence analyzed the influence of the frequency-dependent dielectric constant on the impact current dispersal of grounding electrode. The results show that there exists a big difference in transient grounding resis- tance of grounding electrode whether to take the frequency characteristics of soil dielectric constant into consideration or not. The transient grounding resistance is significantly influenced by both the wavcform and amplitude of impulse current longer wave front time corresponds to higher partial peak of transient grounding resistance; for the same impulse current wave form, higher amplitude corresponds to lower partial peak value of transient grounding resistance.