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What is a ground resistance tester?

time:2020/12/13   source:华天电力  reading:557 time

Grounding resistance testers check whether the actual grounding systems in power stations, power distribution systems, factories, communication systems, and lightning arrester installations are appropriate. These testers also use the Ohm’s law method. They often use three-pole or four-pole configurations. The pole ground resistance tester is the most common.

When the three-pole method tester is working, the path from the ground rod 3 to the ground rod 1 provides a known current. In the resistance test of the potential drop method, the voltage returned to the ground rod 2 of the electrode under test is measured at different points on the path.

Earth Resistance Tester.png

Since the grounding resistance value is affected by many factors, the resistance and distance measured at different points are not linear. In order to ensure the reliability of grounding installations and verify these installations, it is necessary to draw a "resistance-distance" chart. The ground resistance of a device refers to the ground resistance of ground rod 2 at 62% of the distance between ground rod 1 and ground rod 3.

Move the grounding rod 2 from the end close to the grounding rod 3 to the grounding rod 1 to draw a grounding resistance chart. When the test method is appropriate, the resistance value at the 62% point should be on the flat section.

From the perspective of the calibrator designer, the challenge is to provide a large resistor array that can handle the AC current provided by these testers, up to 400 mA; and provide enough resistance values to make it Check the performance of the ground resistance tester. As mentioned above, many modern electrical/electronic calibrators use the method of synthetic resistance to accurately provide millions of different output values, thus thoroughly verifying the 6.5-digit digital multimeter (DMM) The resistance measurement function on the above, a limitation of the calibrator using the synthetic resistance method is that it does not have the ability to handle large currents. They are very suitable for digital meters and analog voltage/ohm meters, but they cannot withstand the ground resistance tester. Hundreds of milliamps of current.

One solution is to use a matrix of discrete resistors, and use real resistors that can withstand this power to provide a resistance output with a resolution of 3.5 bits. The calibrator is suitable for three-pole and four-pole grounding resistance testers, and two ends/four ends. Ohmmeter.

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