Understanding the Loop Impedance Test

The loop impedance test, commonly conducted for single electrode measurements or small earth grid installations, serves as a valuable validation tool of earth grid performance alongside conventional tests.

The performance testing of isolated earthing installations using overland leads for current injection can often pose significant safety risks or practical challenges due to environmental constraints. In these cases, the loop impedance test performed on individual electrodes of the earth grid may be the only viable, safe-to-conduct option.

This paper explores the feasibility and limiting factors of utilising loop impedance test results from individual electrodes within a multi-electrode earthing system, to estimate the earth grid performance. The measurement method is analysed in relation to the effects of mutual earth resistance, earth grid layout and characteristics of the loop impedance test.