Prototype of a measurement device for frequency dependent soil electrical properties

Abstract

Studies show that grounding potential rise and lightning performance of transmission lines are significantly influenced by frequency dependent soil properties (resistivity and permittivity). In order to perform calculations of the transient grounding characteristics more accurately, additional experimental data for different soils is needed. Currently, field measurements of the frequency dependent soil properties can take a significant amount of time. This limits the amount of available experimental data. Thus, for conducting a large number of measurements, a convenient measurement device is needed. Several parameters of the measurement device for the frequency dependent soil electrical properties are discussed in the article (such as preferable generated waveform, the amplitude of the signal, input impedance of the voltage measurement probe, isolation between measurement circuits), and a prototype of the device is presented. A critically important factor for this kind of measurements is high impedance between the current and voltage measurement circuits. In order to achieve proper isolation between the circuits, the optically-isolated probe was made for the voltage measurements. An example of measurements with the dipole-dipole electrode array for high-resistivity soil is presented. Further improvements for the measurement device are also suggested in the article. With these improvements, the measurements can be almost as fast and simple as those made with a conventional soil resistivity meter.