1、 Precision measurement method for grounding resistance

Precision measurement of grounding resistance adopts a three wire connection. After the auxiliary grounding rod and test line are connected, switch the function to measure resistanceRMode, press the button“TEST”Press the key to start the measurement, the LED indicator light flashes during the measurement, the LCD countdown displays, the indicator light goes out after the measurement is completed, and the LCD displays the measurement value.

Starting from the tested object, insert the auxiliary grounding rod into the ground in a straight line every 5-10 meters, and connect the grounding test line (red, yellow, green) from the instrumentHTheSTheEThe interface starts to connect to the auxiliary current pole correspondinglyHAuxiliary voltage poleSThe tested grounding electrodeEUp there. As shown in the diagram:

2、 Simple method for measuring grounding resistance

This method is a simple measurement method that does not use auxiliary grounding rods. It uses the existing grounding electrode with the smallest grounding resistance value as the auxiliary grounding electrode, and connects two simple test lines (i.eHTheSInterface short circuit).

Metal buried objects such as metal water pipes and fire hydrants, common grounding of commercial power systems, or lightning protection grounding electrodes of buildings can be used to replace auxiliary grounding rodsHTheSPay attention to removing the oxide layer from the selected metal auxiliary grounding body connection point during measurement.

The simple test wiring for grounding resistance is shown in the following figure, and other operations are the same as precision measurement.

The simplified method for measuring grounding resistance has an instrument reading of the sum of the grounding resistance value of the tested grounding body and the grounding resistance value of the commercial grounding body, that is:

RE=RX＋re

among whichRERead the value for the instrument;

RXThe grounding resistance value of the tested grounding body;

reThe grounding resistance value of common grounding bodies such as commercial power systems.

So, the grounding resistance value of the tested grounding body is:

RX=RE－re

Use a simple method to measure grounding resistance, and try to choosereThe grounding body with a smaller value is used as an auxiliary grounding electrode, so that the instrument reading is closer to the true value. When measuring, please prioritize using metal water pipes and fire hydrants as auxiliary grounding electrodes.

3、 Double clamp method for measuring grounding resistance value

The double clamp method is suitable for measuring independent multi-point grounding systems, as shown in the figure below. In multi-point grounding systems, there is no need to drill ground stakes to measure the grounding resistance value. Two current clamps, A and B, are clamped into the tested grounding downlead at the same time. Note that the two current clamps should be in the same direction and maintain a distance of more than 30cm. The two current clamps should not be interchanged, otherwise errors may occur

Press the red button on the instrument panel“TEST”Press the key to start the test, and after the test is completed, stable data will be displayed, which is the grounding resistance value of the tested grounding bodyR=Re+R1//R2//R3WhenR1//R2//R3<When, it can be approximated asR≈Re.ES3002 Dual Clamp Multi functional Grounding Resistance Tester (Multi functional Type)Only then does this method exist.