Effects of Seasonal Variations on High Voltage Substation Grounding Grids - Measured and Computed Results

S. Tee, F.P. Dawalibi, and R. Yonza (Canada)


Substation Grounding, Seasonal Resistivity Variations, Electric Safety


The primary objective of this paper is to realistically assess the impact on the overall ground system performance and measurements of a transmission station due to a complex environment including; a very inhomogeneous soil structure, a microwave site, an auxiliary ground site, a nearby lake and slag pool, multiple transmission line equipped with skywires, a distribution line neutral, pole grounds and a neighbouring town distribution network while accounting for significant seasonal resistivity variations of top soil layers as required by IEC Standard 61936-1. Since the present North American high voltage substation grounding standards (ANSI/ IEEE Standards 80 and 665, respectively) do not directly address this issue and very little information exists in other grounding literature, this study focuses on the behaviour and safety of the grounding system in summer, winter and spring soil conditions.

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