Ground Resistance Testers are a class of safety testers with unique challenges. Electrical technicians use these testers to check that the actual grounding system in the power station, power distribution system, plant, communication system, and arrester unit is appropriate. These testers also use Ohm's law. They are often used in three- or four-pole configurations, with a three-pole grounding resistance tester being the most common.
Since the grounding resistance value is affected by many factors, the resistance measured at different points is not linear with the distance. In order to ensure the reliability of the grounding installation and to verify these installations, a "resistance-distance" chart is required. earth wire The grounding resistance of a device refers to the grounding resistance of the grounding bar 2 at a distance of 62% between the grounding rod 1 and the grounding rod 3. As shown in the figure.
From the calibrator's point of view, the challenge is to provide a large array of resistors that can handle the AC currents provided by these testers up to 400 mA; and provide enough resistance to be sufficient Check the performance of the ground resistance tester.
As mentioned above, many modern electrical/electronic calibrators use synthetic resistors to accurately provide millions of different output values, thoroughly testing the resistance measurement function on a 6.5-digit digital multimeter (DMM). One limitation of the calibrator using the synthetic resistance method is that it does not have the ability to handle large currents. They are ideal for digital meters and analog voltage/ohmmeters, but they cannot withstand the hundreds of milliamps of current provided by the ground resistance tester.