How to test grounding resistance

The grounding resistance test method is as follows:

1, double-line method

Conditions: there must be a well-grounded ground wire, such as PEN, and the measured result is the sum of the resistances of the measured ground wire and the known ground wire. If it is known that the ground is much smaller than the resistance of the measured ground, the measurement result can be taken as the result of the measured ground.

Suitable for: areas with dense buildings or cement floors. Seal the place that cannot be used for piling.

Wiring: E+ES is connected to the measured ground, and H+S is connected to the known ground.

2. Three-line method

Conditions: There must be two grounding rods: an auxiliary ground wire and a detection electrode. The interval between each grounding electrode is not less than 20m. The principle is to add current between the auxiliary ground and the measured ground, and measure the voltage drop between the measured ground and the detection electrode. The measurement results include measuring the resistance of the cable itself.

Suitable for: foundation grounding, construction site grounding and lightning protection grounding.

Wiring: S is connected to the detection electrode, H is connected to the auxiliary ground, and E and ES are connected to the measured ground.

3. Four-line method

Basically, like the three-wire method, it replaces the three-wire method when measuring low grounding resistance, eliminating the influence of measuring cable resistance on the measurement results. When measuring, E and ES must be directly connected to the measured ground respectively. This method has the highest accuracy.

4, single clamp measurement

When grounding at multiple points, measure the grounding resistance of each grounding point, and do not disconnect the grounding connection to prevent danger.

Suitable for: multi-point grounding, unable to disconnect, measuring the resistance of each grounding point.

Wiring: use current clamp to monitor the current of the connection point to be measured.

5, double clamp method

Conditions: multi-point grounding, no auxiliary pile, single grounding measurement.

Wiring: Connect the current clamp specified by the manufacturer to the corresponding socket, and clamp the two clamps on the grounding conductor. The distance between the two fixtures should be greater than 0.25m. ..