Various methods for measuring ground resistance

1. Precision measurement method of grounding resistance The

precision measurement of grounding resistance adopts three-wire connection. After the auxiliary grounding rod and test line are connected, switch the function to measure resistance R mode, press the "TEST" button to start the measurement, the LED indicator flashes during the measurement, and the LCD countdown is displayed. After the measurement is completed, the indicator light goes out and the LCD displays the measured value. Starting

from the object to be measured, insert the auxiliary grounding rod into the ground in a straight line every 5 to 10 meters, and connect the grounding test lines (red, yellow, green) from the H, S, E interfaces of the instrument to the auxiliary current electrode H, auxiliary voltage electrode S, and the measured grounding electrode E. As shown in the figure:

2. Simple method for measuring ground resistance

This method is a simple measurement method without using auxiliary grounding rods. The existing grounding electrode with the smallest grounding resistance value is used as the auxiliary grounding electrode, and two simple test lines are used to connect (that is, the H and S interfaces are short-circuited).

Metal water pipes, fire hydrants and other metal buried objects, common grounding of commercial power systems or lightning protection grounding electrodes of buildings can be used to replace auxiliary grounding rods H and S. When measuring, pay attention to removing the oxide layer at the connection point of the selected metal auxiliary grounding body. The

simple test wiring of ground resistance is shown in the figure below, and other operations are the same as precision measurement.

The simple method measures the grounding resistance. The meter reading is the sum of the grounding resistance value of the ground body under test and the grounding resistance value of the commercial ground body, that is:

RE=RX＋re

Where: RE is the meter reading value;

RX is the grounding resistance value of the ground body under test;

re is the grounding resistance value of the common ground body such as the commercial power system.

Then, the grounding resistance value of the ground body under test is:

RX=RE－re

When using the simple method to measure the grounding resistance, try to choose a ground body with a small re value as the auxiliary grounding electrode, so that the meter reading is closer to the true value. When measuring, please give priority to metal water pipes and fire hydrants as auxiliary grounding electrodes.

3. Double-clamp method for measuring ground resistance

The double-clamp method is suitable for measuring independent multi-point grounding systems. As shown in the figure below, in a multi-point grounding system, there is no need to drive ground stakes to measure the ground resistance value. Clamp two current clamps A and B into the ground lead to be measured at the same time. Note that the two current clamps must be in the same direction and keep a distance greater than 30cm. The two current clamps must not be interchanged, otherwise errors will occur.

Press the red "TEST" button on the instrument to start the test. After the test is completed, stable data will be displayed, that is, the ground resistance value of the ground body under test is R=Re+R1//R2//R3. When R1//R2//R3<