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SEPTEMBER 8, 2013 BY HURRICANE193

Wenner Four Pin Method for Soil Resistivity Test

(http://hurricane193.files.wordpress.com/2013/09/05-wenner-4-point-test.jpg)Before design grounding system for the plant, soil resistivishall determine first. This value of soil resistant will be an input idesigning grounding system later (i.e. substation grounding, engine hagrounding and pump house grounding). To determine the soil resistivitvalue, there are several steps to be done.

First of all we will discuss a method used to determine the soil resistivivalue.

This method known as Wenner four-pin method, developed by Dr. Frank Wenner, US Bureau oStandards in 1915. On these methods used four electrodes, two for current injection and two for voltagmeasurement. The four electrodes embedded to the ground in straight line, the two outer electrodes acurrent electrode and two inner electrodes to measure voltage drop due to resistance of soil path whecurrent passed between the outer electrodes.

(http://hurricane193.files.wordpress.com/2013/09/wenner-4-pin-method.jpg)Figure 1. Wenner Four PiArrangement

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The resistance can be measure and resistivity calculated according the following formula.

(https://reader009.{domain}/reader009/html5/0308/5aa0d6466f378/5aa0d648c7df6.jpg)

Where: ρ = Resistivity in Ohm-cm

  a = spacing between pin in cm

  R = Resistance measurement in Ohm

The depth of electrode shall not exceed the value of a/20

It should be noted that measurement made in this manner indicate average resistivity over a depth osoil corresponding to the spacing between adjacent pin/electrode.

Before perform the test, please take attention to the below condition:

1. Prepare the coordinate to be tested.This coordinate normally located at the equipment (i.e. substation, turbine hall, compressor areaand pump house) location.

2. This test is better to perform in flat location, for 10 meter depth assessment needed 30 meter flatarea.

3. Cable path shall not crossing any metallic material.

(http://hurricane193.files.wordpress.com/2013/09/wenner-method-principle.jpg)Figure 2. WennerMethod Work Priciple

The following step used to test the soil resistivity in this method:

1. Placed the soil resistivity measure equipment on the center of the assessment location.2. Put two potential electrode on the left and right side point of view based on the distance te

required. This electrode embedded from 5 to 10 cm to ground, based on the soil condition.3. Put two current electrode on the left and right side point of view based on the distance test require

This electrode embedded from 5 to 10 cm to ground based on the soil condition.4. Connect all electrodes cable with the soil resistivity measuring equipment’s.5. Energize the electrode with the power supply form soil resistance measuring equipment’s.6. Please make sure no one touch the electrode when the electrode energize.

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7. The value of soil resistivity will calculate and appear on the soil resistivity measuring equipmeLCD’s or monitor.

Repeat step 2 until step 6 based on the depth required.

(https://reader009.{domain}/reader009/html5/0308/5aa0d6466f378/5aa0d6497befa.jpg)Figure 3. Soil Re

Any comment and discussion, please fill the comment field below

Reference:

NEEC – Soil Resistivity

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This entry was posted in My Story and tagged compressor grounding, Earthing, engine hallgrounding , Frank Wenner, Grounding , Procedure for Soil Soil Resistivity Test, pump house groundinSoil Resistance, Soil Resistivity, Soil Resistivity Test, substation grounding , turbine hall, turbine hallgrounding , Wenner Method, Wenner Soil Resistivity Test Method. Bookmark the permalink.

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