Tests and Monitoring of Grounding Systems in HV/MV Substations

Each grounding system (GS) needs periodical measurements to control its adequacy to the safety conditions. The tests of step and touch voltages are the sole measurements available in urban or industrial areas with reduced accessibility. In fact, in these areas, the classic measurements used to verify the electrical characteristics of the GS generally present some operational difficulties. The auxiliary current electrodes can only be located at short distances, and thus, the test methods and techniques result in conservative values in comparison with the prospected true values measurable by adopting a remote auxiliary electrode. The locations of auxiliary current electrodes at short distance make it easier to keep them permanently installed and to permit the monitoring of the adequacy of GS. This paper presents the measuring touch/step voltages procedure that provides conservative results showing some case studies done in GS of high voltage/medium voltage substations. It is essential to have the map of the constitution and configuration of the GS to know its data and the location of the various equipment and buildings, the presence of extraneous conductive parts inside, and in proximity of the substation, such as other GS. The field measurements require a good experience of the operator that can be learned by carrying out measurements in cases of GS with influence zone accessible, so that it is possible to compare the traditional method with a remote electrode and the method at short distance.