How do you measure grounding resistance?
Ground connections are made by driving the grounding electrode into multiple positions. The grounding electrode consists of a metal tube or conductive plate connected to the earth.
BY2571 Ground Resistance Tester
Different materials are used in the fabrication process, such as copper, aluminum, steel or galvanized iron. There are many factors that affect the grounding resistance, such as soil composition, temperature, moisture content and electrode depth. Earthing allows leakage currents to flow out safely and is connected to an automatic cut-off device (to ensure power supply). An earthing system contains different components such as earth electrodes, main earth terminals or rods, earth conductors, protective conductors, equipotential connection conductors, electrically independent earth electrodes (for measurement), terminal fittings, connections, welding kits and other materials.
What are the methods of measuring grounding resistance?
Depending on the type of neutral system, the type of installation (residential, industrial, urban environment, rural environment, possibility of disconnecting the power supply), different methods of grounding resistance measurement are used. Four variables that affect the grounding resistance of a grounding system include:
1, Composition of the soil
2, Water content of the soil
3, Temperature of the soil
4, Depth of the electrode
The electrical resistance of a grounding electrode is dependent on the resistivity of the soil the electrode is inserted into. Therefore, it is critical to measure the resistivity during the design of any grounding device.
The grounding resistance is the resistance of the grounding electrode measured to perform a resistance check. With additional measurements such as voltage, the test electrode moves 10% of the original voltage electrode into the grounding system, separating it from its initial position and 10% closer than its original position. When both agree with the measurement within the required level of accuracy, the test stake is placed in the correct position and the resistance can be obtained by averaging all three results.
Before starting any ground resistance measurement, the maximum value for proper grounding needs to be measured. There are six basic test methods for measuring ground resistance:
1. Four-point method (Wenner method)
2. Three-terminal method (attenuation potential method/68.1% method)
3. Two-point method (dead earth method)
4. External clamp test method
5. Slope method
6. Star-delta method