SAFE MEASUREMENT OF GROUND RESISTANCE Presented at the Society for Mining, Metallurgy and Exploration (SME) Symposium

The mining industry uses a large amount of electric power. Their equipment is subject to extreme environmental conditions and mechanical shock. A significant number of electrical accidents are a result of improperly grounded electrical equipment. Federal regulations require the safety ground bed resistance to be measured once a year or after modifications for the Metal/Nonmetal Mining Industry. Coal mine regulations require connection to a low resistance ground medium. A ground resistance measurement can be accepted as evidence of compliance with these regulations. Most commercially available instruments used to measure the ground bed resistance require the ground conductor to be disconnected and the power system disconnected for safety reasons. The “fall of potential ” method requires auxiliary ground rods and approximately two hours to complete the test. Although a new instrument was initially thought to measure the ground bed resistance immediately without isolating the ground bed, field tests have shown this method is not accurate. In some cases, a continuous measurement of the ground resistance is desired. A monitor has been developed and is presently being evaluated at several mines. These installations will be discussed