Earth Integrity Test-Complexity of and Insight Into the Interpretation of Field Test Results

The purpose of an earth integrity test, as described in IEEE 81-2012, is to assess the healthiness of earth connections through the measurement of the resistance or impedance of the connection path. Undertaking such a measurement is laborious and requires skill, good instruments and current injection equipment. In this paper, field experiences in conducting such tests using both DC and AC currents are shared in detail. The test results from two different sites are analyzed, and the calculated circuit parameter is included in an equivalent circuit diagram. A resistance network is modeled in EMTP software for a sample earth grid to find the equivalent resistances across various nodes. The importance of carefully measuring low resistance values and the complexities of interpreting the test results are highlighted. Reference values for resistance measurement based on different standards are summarized and analyzed. This paper includes observations for improvement on test reference values stated in the relevant IEEE Std. 81-2012 and BS 7430:2011. Despite the earth integrity test is widely used for the primarily testing of joints of earth grid installations in the United Arab Emirates, interpretation of test results is a challenge to field engineers.