Considerations on Earthing Impedance Measurement using Low-magnitude Variable-frequency Currents

This paper deals with the measurement of earthing impedance of systems subjected to low magnitude variable-frequency currents. Measurement fundamentals are briefly discussed and some factors that can influence the results are underlined. Experimental investigations are conducted to examine the impact of certain selected factors namely, the length of the test leads and the angle between them as well as the wire length between voltage transducer and injection point. At low frequencies, the results indicate that long test leads with a 90 degree angle represents the best measurement configuration. This configuration is considered for high frequency where the effect of the test wire length is studied. The results show that the length of the measurement wire results in a significant inductive component, which has different magnitude and occurs at different frequencies according to the wire length and the impedance of the earthing system. Such findings may help pave the way for the initiation of the standardization in the measurement of high frequency impedance of earthing systems.