ASSESSING EARTHING SYSTEM THROUGH GEOELECTRICAL INVESTIGATION OF SOIL RESISTIVITY ON A SITE IN OYO TOWN, OYO, NIGERIA.
Keywords:
Vertical Electrical Sounding, Geoelectrical Survey, Soil resistivity, EarthingAbstract
The absence of an effective earthing system can lead to the exposure of electrical power systems to high-magnitude transient currents and voltages with rapid rise times, posing risks of equipment damage and harm to individuals. Soil resistance plays a crucial role in the design of an earthing system. Geophysicists commonly employ the electrical resistivity method, a widely used geophysical technique, to assess subsurface properties and identify suitable locations for earthing installations. This method utilizes principles of electrical conductivity and resistivity to characterize the subsurface. This study focuses on the application of the Geo-Electrical resistivity
survey technique to investigate soil conditions and determine earthing properties within Ajayi Crowther University in Oyo State, Nigeria. Ten Vertical Electrical Soundings (VES) were conducted using the Schlumberger Configuration. The VES data were interpreted using the partial curve matching method. The findings revealed the presence of about four unique geo-electric sequences in the surveyed area, namely the topsoil, weathered layer, laterite layer, and bedrock. The thickness of the topsoil layer was found to vary between approximately 0.5 m and 2.9 m. Among the VES measurements conducted, VES 4 and VES 5 exhibited the KH curve type, while
VES 9 displayed the QH curve type. Based on the survey results, VES 9 was identified as the most suitable site for an earthing system due to its lowest resistivity value (< 15 ohms-meter). However, further research is recommended to investigate VES 4 for potential alternative locations. Although VES 4 did not exhibit the lowest resistivity value among the surveyed VES points, it may still hold significant potential for earthing system placement.
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