Measurement of resistivity of surface layer material in laboratory

This paper presents the laboratory measurement of substation surface layer wet rock resistivity with tap water and water solution of different conductivities made of salt like sodium chloride. The result obtained are co-related with rain water resistivity using least square method which represents worst case design of substation grounding grid. Moreover, the resistivity is measured for deterioration and contamination of surface material due to air born dust, mud deposition and mixing with native soil beneath the surface layer. The resistivities obtained are compared with original wet resistivity of surface material in order to maintain it over the lifespan of substation. Further, the importance of thin layer of high resistivity surface material used for covering the substation and its measurement for economic, safe and reliable operation of substation equipment and safety of person is discussed.