Substation Ground Impedance: Comparative Field Measurements with High and Low Current Injection Methods

This paper describes ground electrode impedance field measurements and their analysis at Hydro-Quebec´s Yamaska substation, using both high and low current injection methods. The results from both techniques are shown to compare satisfactorily. In the low current injection method, numerous measurements were performed in different directions, describing how the mutual coupling effects between the auxiliary current and potential probes can be removed with adequate analytical tools. A comparison is also made between ground impedance values at 60 and 70 Hz. Finally, an appendix includes characteristics of some of the equipment used during these measurements.