Ground Testing in the Mines

Consider the Mine Safety and Health Administration (MSHA) Standard 56/57.12028 (Testing Ground Systems). The intent of this standard is to ensure that continuity and resistance tests of grounding systems are conducted on a specific schedule. These tests will alert the mine operator if a problem exists in the grounding system which may not allow the circuit protective devices to quickly operate when faults occur. With the exception of fixed installations, numerous fatalities and injuries have occurred due to high resistance or lack of continuity in equipment ground systems. These accidents could have been prevented by proper testing and maintenance of grounding systems.

Grounding systems typically include the following:

Operators shall conduct the following tests:

The rest of the standard indicates certain instances where the testing of equipment grounding conductors and grounding electrode conductors is not required (not subject to vibrations; fail-safe ground wire monitor used to continuously monitor the grounding circuit), and that a record of the most recent resistance tests must be kept. Note that, in all situations, installed grounding electrodes (ground rods) must be tested on an annual basis. You can access the MSHA regulations at

What does this standard mean? All mines must test (and keep a record) their grounding electrodes. Depending on the specific requirements and test environment, AVO offers four ground testers (DET62D, 250260, DET5/4R, DET/5/4D, and DET2/2). Contact Jeff Jowett, Applications Engineer at AVO International (215-283-2291) for a recommendation on choosing the correct instrument.