Contact impedance of grounded and capacitive electrodes
Contact impedance of grounded and capacitive electrodes
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DOI：
10.1093/gji/ggs091
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发表时间：
2013-04
影响因子：
2.8
通讯作者：
A. Hördt;P. Weidelt;A. Przyklenk
中科院分区：
文献类型：
--
作者：
A. Hördt;P. Weidelt;A. Przyklenk
电极的接触阻抗决定了在给定电压下有多少电流可以注入到地面。如果接地电阻很大，则容性耦合可能比电流耦合更优越上级。电容电极阻抗的标准方程假定半空间是理想导体。然而，在高频电阻接地上，接触阻抗将取决于地下的电特性，即电导率和介电常数。在这里，我回顾现有的方程的电阻的电流耦合，球形电极在一个完整的空间。我的理论扩展到一般情况下，一个球体在一个球形分层fullspace可能会显示电流和电容耦合。对于电容耦合电极，如果全空间中的位移电流变得与传导电流一样大，则理想传导全空间（或半空间）的常见假设就崩溃了。对于1000 μ m的中等电阻介质，频率大于100 kHz时就是这种情况。对于1 M Ω左右的极高介电系数，过渡频率降低到100 Hz。因此，原则上，可以通过测量电极接触阻抗的幅度和相位来确定电阻率和介电常数。
The contact impedance of electrodes determines how much current can be injected into the ground for a given voltage. If the ground is very resistive, capacitive coupling may be superior to galvanic coupling. The standard equations for the impedance of capacitive electrodes assume that the halfspace is an ideal conductor. Over resistive ground at high frequencies, however, the contact impedance will depend on the electrical properties, i.e. electrical conductivity and permittivity, of the subsurface. Here, I review existing equations for the resistance of a galvanically coupled, spherical electrode in a fullspace. I extend the theory to the general case of a sphere in a spherically layered fullspace which may display both galvanic and capacitive coupling. For a capacitively coupled electrode, the common assumption of an ideally conducting fullspace (or halfspace) breaks down if the displacement currents in the fullspace become as large as the conduction currents. For a moderately resistive medium with 1000 �m this is the case for frequencies larger than 100 kHz. For very high resistivities around 1 M�, the transition frequency reduces to 100 Hz. Thus, in principle, one may determine electrical resistivity and permittivity by measuring magnitude and phase of the electrode contact impedance.