1. What is soil resistivity?
Soil resistivity is the product of the average value of soil resistivity per unit length and cross-sectional area, expressed in Ω · m. Soil resistivity is a basic parameter often used in the design of electric power systems, which generally needs to be obtained through on-site testing.
Soil resistivity is a commonly used parameter in grounding engineering calculations, which directly affects the grounding resistance of grounding devices, ground potential distribution of grounding grids, contact voltage, and step voltage. Soil resistivity is an important factor in determining the resistance of a grounding body. In order to reasonably design a grounding device, it is necessary to measure soil resistivity so that the measured resistivity can be used as a calculation parameter for grounding resistance.
2.Test method for soil resistivity:
This test requires the user to place four equally spaced auxiliary probes underground to determine the actual soil resistance, traditionally measured in ohm centimeters or ohm meters. This test must be conducted throughout the area to determine the soil value at all locations. This test was conducted at different intervals of 5 to 40 feet to determine resistance values at different depths. This knowledge will assist in designing and implementing the correct ground system to meet specific site requirements. The following are the steps to measure soil resistivity:
1. Place four test rods evenly apart on a straight line and hammer them into the ground for inspection, with a depth not greater than one twentieth of the distance between adjacent rods.
2. Connect the ground resistance tester to these four piles.
3 • Then select and execute the DC test option on the tester and record the resistance number R
4 • Then use the following formula to find the soil resistivity r in ohms per centimeter:
r =2 ρ aR
Where: R=resistance value (ohms), a=spacing of test piles, in meters.
