Grounding resistance measurement analysis of grounding system in vertical-layered soil

How to precisely measure the grounding resistance of substations is the fundamental factor to guarantee the safe operation of power systems. The placement rules of test electrodes for the grounding resistance measurement of grounding system in vertical-layered soil were analyzed by the numerical method in this paper. The actual demanded location of the test potential electrode respective to the true grounding resistance of grounding system in different measuring directions changed (in a wide range) when the grounding system was arranged in different soil models. The test error of 0.618 method to measure grounding resistance sometimes is very high. The test route that the test circuit is in parallel with the vertical boundary is recommended for measuring the grounding resistance of grounding system in the vertical-layered soil area. The scientific and suitable measuring method of grounding resistance is based on analyzing the actual soil model and the grounding system structure to obtain the suitable test route and choose the correct compensated point location of the potential electrode.

I. Introduction

The grounding system of a substation is a fundamental countermeasure to guarantee the safe operation of power systems [1]. The grounding resistance is an important index of grounding systems for substations and power plants, and is also a parameter to measure the efficiency, safety of grounding systems, and to check whether the grounding systems meet the demand of design. Due to the nonuniformity of soil and measuring error of soil resistivity data and some other factors, which cannot be considered in simulating analysis, the designed value of grounding resistance must be checked by the field test after the grounding system is constructed [2], [3]. On the other hand, in order to examine the actual condition of The Grounding system of an operating substation, the grounding resistance must be measured periodically. The measurement of the grounding resistance is routine work to ensure the safe operation of power systems in China [4].