Beneath every substation, there is a grounding grid. It provides a proper grounding of all apparatuses in substations. The purpose of this grid is to improve the safety of both personnel and apparatuses in a substation. Over time, this grid deteriorates due to corrosion, ground movements, grid fatigue, high energy conductance (lightning) and construction damage. All of this can interrupt the grid integrity and cause various safety problems.
There are various test procedures to inspect the state of grounding systems. The most relevant standard is IEEE 81 which refers to practical test methods and techniques for measuring the electrical characteristics of grounding systems.
DV Power developed GGT500 instrument, which is specially designed for inspection of substation ground grid integrity. The test is performed by injecting continuous DC current between the desired measurement point and reference point. Finally, the condition of the ground grid is determined based on the obtained information about the current path and voltage drop.