Mike Dolt Enterprises
Mike Dolt Enterprises
User: STAR87, Location: Leesburg, VA
Asked on: Sunday, April 10, 2011 at 12:22 am EDT
Answered on: Tuesday, May 14, 2024 at 4:00 am EDT
Question: After we finished from making earth network around one of our projects (building 3500 m2) i wanna measure the earth resistance i have read that there r a lot of method to measure this resistance but my question is aboutthe measure of tingle(delta) which make three rods as triangle equal in every rod long and then starting measurethere is another methodis to put in earth 4 rods one of them already part of earth network and the distance between rods must be equal and the part which in earth must be equal for 4 rodswhich method is th best ..what is the proper long for the rods which will be on earth?
Best Method
The most accurate and widely used method for measuring earth resistance is the
Four-Terminal Method. This method uses four rods placed in the ground: Current Rod
Supplies current to the earth.
Voltage Rod (E)
Measures the voltage across the earth resistance.
Voltage Rod (I)
Measures the current flowing through the current rod.
Ground Rod (R)
Already part of the earth network, connected to the current rod.
Procedure
1. Place the Current Rod and Ground Rod at the farthest ends of a straight line.
2. Place the Voltage Rods at equal distances (L/2) from the Current Rod, perpendicular to the line.3. Supply a known current (I) to the Current Rod.
4. Measure the voltage (V) across the Voltage Rods.5. Calculate the earth resistance using Ohm's law: R = V / I
Rod Length
The proper length for the rods depends on the soil conditions. Generally, the following guidelines are recommended:
Sandy soil
Rods should be 0.5-1 meter long.
Clayey soil
Rods should be 1-1.5 meters long.
Triangle Method
The Triangle Method is less accurate than the Four-Terminal Method. It involves placing three rods in a triangular formation and measuring the resistance between each pair of rods. The average of the three measurements is taken as the earth resistance.
Advantages of Four-Terminal Method
Measures true earth resistance, excluding the resistance of the connection to the ground rod. Compensates for any voltage drop in the current rod. More accurate and reliable results.
Advantages of Triangle Method: Simpler to set up and requires fewer rods.* Can provide an approximate estimate of earth resistance.For critical applications where accurate earth resistance measurements are essential, the Four-Terminal Method is the preferred choice. Flag for review