Testing continuity of grounding grid using the AC current injection method

We propose here a cost-effective, realistic method for testing the continuity of the grounding grid and for identifying its weak points or discontinuities. The proposed method involves injecting an ac current of ~200 A frequency not 60 Hz or 60 Hz harmonic into a grounding grid. The purpose of the frequency setting is to be able to distinguish the magnetic field produced by the injected current when the substation is energized. The magnetic field generated by the current flowing in the buried grid conductors is then measured above the ground. A strong magnetic field indicates that the grounding grid is in good condition; a weak magnetic field indicates that some damage may exist. Two field tests were conducted to demonstrate that the proposed method works effectively in determining the continuity of the grounding grid.