Geology and geochemistry are dominant factors controlling ground resistivity and thus can be used to help in selecting electrical substation sites with good grounding conditions. A good substation ground grid is important for the protection of people, equipment and the environment from excessive ground plane voltage rise. The objectives of the first phase of this project are to identify from the literature, geological and geochemical factors that can be used as markers to improve site selection and, secondly, to evaluate the quality, accessibility and applicability of publically available data in selected jurisdictions. The objective of the second phase of the study is to develop and test a practical methodology for locating promising substation sites with low soil resistivity.
A literature review of geological and geochemical markers that can be used predictively to estimate ground resistivity was completed. Markers of interest include soil clay content, abundance of faults and fractures, ore mineral concentration, ground water saturation, salinity and temperature. The availability and quality of data was investigated in four jurisdictions: British Columbia, Washington State, Ontario and New York State. Federal data sets were also included in the analysis. Both surface mapping (surficial and bedrock geology) and subsurface borehole data sets were investigated in each jurisdiction.
Further investigation in a second phase of this study is recommended to quantify the predictive strength of individual markers and to develop a field-verified methodology that can be used by design engineers. The results will be presented in a form usable in ground system design and in developing financial decision matrices used in the substation site selection process.
Geology, geochemistry, substation site selection, ground resistivity, conductivity, British Columbia, Washington State, Ontario, New York State