College of Engineering

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Browsing College of Engineering by Author "AKINYEMI, MOFOLORUNSHO"

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    ASSESSMENT OF THE EFFECT OF SOME FACTORS AFFECTING SOIL RESISTIVITY FOR OPTIMAL PERFORMANCE OF A GROUNDING SYSTEM.
    (2024-09-25) AKINYEMI, MOFOLORUNSHO
    ABSTRACT The impedance of the discharge path of a fault current defines the quality of a grounding system. Thisstudy assessed the effect of depth (D), temperature (T), moisture content (MC) and soil texture (ST) onsoil resistivity () for optimal performance of a grounding system. The measurements for two differentseasons which are rainy season (July 2023) and dry season (January 2024) were carried out at 10locations in Federal University of Agriculture, Abeokuta as a case study. These locations wereCOLENG, Postgraduate (PG) School, COLPHYS, Health Centre (HC), Works and Services Unit(WSU), COLANIM, COLVET, COLPLANT, Student Union Building (SUB) and COLBIOS. The wasmeasured via Wenner method at D of 0.150, 0.450, 0.756, 1.110 and 1.490 m automatically selected bythe Herojat Rhomega-Smart Resistivity Meter deployed. The MC and ST were determined for the sameD values by laboratory analysis of five samples of 5 kg soil from each location. The ST class wasidentified using IEEE Standard 81-2012 and the soil T at different D values was measured using athermometer. The relationship between the dependent variable () and the independent variables (MC, Tand D) was modelled via the use of multiple linear regression (MLR) for each location for both seasons. The level of contribution of D, T and MC to was determined by the coefficient ofdetermination (R 2). The rainy season measured at COLENG, PG School, COLPHYS, HC, WSU,COLANIM, COLVET, COLPLANT, SUB and COLBIOS ranged between 31.6-262.0, 78.5-222.5,113.7-222.5, 48.4-167, 91.0-184.0, 61.6-124.7, 122.0-177.5, 190.0-341.5, 100.3-203.0 and 84.7-116.0Ωm, respectively while the dry season values ranged between 123.7-462.5, 106.5-448.5, 178.5-1128.5,271.1-493.0, 111.0-306.0, 70.1-257.5, 140.0-656.5, 320.5-853.0, 188.0-382.5 and 92.2-365.5 Ωm,respectively. These values were typical of three ST classes which included sandy loamy, sandy clayloam and loamy sand. The MC measured for both seasons at the locations ranged between 9.60-20.30,2.06-16.4, 2.39-12.40, 3.40-8.30, 3.80-23.90, 9.40-16.90, 12.20-17.60, 10.10-12.00, 8.40-18.10 and13.20-15.10 %, respectively. Similarly, the soil T measured during rainy season ranged between 28-31,27-30, 30-31, 30-31, 29-30, 29-30, 28-29, 29-30, 29-30 and 29-30oc , respectively whereas the valuesranged between 39-40, 35-36, 37-38, 37-38, 38-39, 37-38, 37-38, 38-39, 37-39 and 35-36oc ,respectively, for dry season. The lowest was measured at nearly all the locations for both seasons at D of 1.490 m where MC was highest and T was lowest. The only exception to this trend occurred at SUBand COLPLANT where was lowest at 0.150 m and HC where the value was least at 0.150 m and 0.450m, respectively, during rainy season. The 20 MLR models developed for the 10 locations for both rainyand dry seasons revealed that MC, T and D collectively contributed better to than the individual variables due to higher value of multiple R 2 recorded. This study showed that the soil resistivity of thetest locations was influenced by soil texture, moisture content, temperature and depth.