A Study on Mutual Coupling between Vertical Grounding Electrodes

Abstract

This paper investigates a mutual grounding impedance between vertical grounding electrodes based on field measurements and FDTD simulations. In the case of vertical electrodes, the mutual impedance between the electrodes is almost independent of the electrode length, and thus an induced voltage is nearly constant as the electrode length becomes longer. This characteristic is different from that of an overhead conductor where the electromagnetic induced voltage is proportional to the conductor length. The greater the separation distance between the electrodes, the smaller the induced voltage same as that of the overhead conductor. The propagation velocity increases as the separation increases. It is found that the velocity is not necessarily proportional to the inverse of the relative permittivity of the earth.