The ground wire resistance mainly includes the ground wire and the ground body itself. The contact resistance between the resistor, the grounding body and the ground resistor, and the grounding wire resistance between the two grounding bodies or the grounding wire resistance of the grounding body are infinite. The resistance of the grounding wire can directly reflect the electrical mutual Contact between. The degree of equipment and "ground protection" also reflects the scale of the grounding grid. The concept of ground wire resistance is mainly used for small grounding networks. With the increase in the coverage area of the grounding grid and the decrease in soil resistivity, the inductance component of the grounding protection impedance becomes more and more important.

The more commonly used methods of testing ground wire resistance mainly include:

1. Two-point method

In this way, the resistors of the two electrodes in series can be accurately measured by connecting the P1 and C1 terminals to the ground protection electrode to be tested, and connecting P2 and C2 to a separate all-metal ground point.

The two-point method is a very simple method to obtain ground wire resistance readings, but it is not as accurate as the three-point method and can only be used as a last resort. This is an effective way to quickly test the phase connections and conductors between the connection points.

Note: The ground electrode under test must be far enough away from the auxiliary contact to exceed its impact range.

2. Three-point method

The three-point method is a thorough and reliable test method. It is used to accurately measure the ground wire resistance of the grounding protection electrode. Use a four-terminal tester to connect the P1 and C1 terminals on the instrument and connect them to the ground protection electrode under test. At the same time, the C2 reference rod can be directly driven into the ground and as far as possible from the electrode. Then the potential reference point P2 can be driven into the ground and C2 through a certain number of points on the straight line between C1 and C1, and record each P2 point Resistor readings.

3. Four-point method

This method is a common method for accurately measuring soil resistivity and is very important for the design of electrical grounding protection. In this method, four small electrodes are driven into the ground at the same depth and equidistant (straight line) and accurately measured.

The moisture and salt content of the soil fundamentally affect its resistivity, and the accurate measurement of soil resistivity is also affected by the existing ground protection electrode; if the buried conductive object in contact with the soil is close enough to change the test current mode, the reading will be Ineffective, especially for large or long objects.

4. Clamping method

The uniqueness of the clamp method is that it can accurately measure resistors without disconnecting the grounding protection. It is fast and simple, and mainly includes grounding protection and total grounding wire resistance in accurate measurement.

It is possible to "clamp" the clamp-type ground protection resistance measuring instrument around the ground protection electrode under test, which is similar to the method of accurately measuring current with a multimeter current clamp. The tester can apply a known voltage through the transmitting coil and accurately measure the current that can pass through the transmitting coil when there is no direct electrical connection to the ground. The receiving coil is tested at high frequency to make the power transformer as small and practical as possible.