The Earth faults are hazardous and hence need proper earthing to prevent fault current from entering into anybody or metallic object. The purpose of earthing is to minimize the effect of transient voltage that occurred due to a strike of lightning.

What are the methods of measuring earth resistance?
There are different earth resistance measurement methods used depending on the type of neutral system, the type of installation (residential, industrial, urban environment, rural environment, the possibility of cutting off the power supply. Four variables affect the earth resistance of a grounding system which includes:

1. The composition of the soil
2. The moisture content of the soil
3. The temperature of the soil
4. The depth of the electrode

The resistance of the earth electrode depends upon the resistivity of the soil in which the electrode is inserted. Therefore, it is crucial to measure the resistivity during the design of any earthing installations.

Earth resistance is the resistance of the ground electrode measured to perform a resistance check. With additional measurements like the voltage, the test electrode moved 10% of the original voltage electrode to the earth system, separating it from the initial position and 10% closer than its original position. When both of them agree with the measurement within the required level of accuracy, the test stakes are placed in a correct position, and the resistance can be obtained by averaging all three results.

Before starting any earth resistance measurements, the maximum value for correct earthing needs to be measured. There are six basic test methods to measure the earth resistance:

1. Four-point method (Wenner method)
2. Three terminal methods (falloff potential method/ 68.1% method)
3. Two-point method (dead earth method)
4. Clamp-on test method
5.  Slope method
6.  Star delta method

Based on the methods mentioned above, Weshine have developed a Earth Tester Series (VS-3000 series), which combines the new lightning protection grounding resistance detection standard, specially for on-site measurement of earth resistance, soil resistivity, grounding voltage, AC voltage.