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Detection Technology

Several methods of grounding resistance tester

time:2020/6/13   source:华天电力  reading:775 time

In the detection of ground resistance, there are many factors that cause the ground resistance tester reading is not accurate. The reasons are summarized in the following aspects:

1. As the ground resistance tester tests the ground resistance of the ground body by sending and receiving the current of the bit rod, mutual interference will occur when the distance between two bit rods and the distance between the bit rod and the ground body is too close, resulting in errors. Grounding body, voltage pole and current pole are arranged sequentially with three points forming a straight line and 20m apart.

2. The depth of the copper wire should be greater than 1/4 of the length of the copper wire, otherwise there will be a test error. Therefore, the drill pipe should be as deep as possible in the test.

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3. Under the condition of "common ground", the grounding device generates a certain grounding voltage to the equipment due to poor insulation or short circuit. If the reading is unstable during the measurement, the power should be cut off for detection, or a disconnect card should be disconnected for detection to avoid the influence of grounding voltage on detection.

4. Poor contact. When the tested object rusts or the test line breaks, the on/off or the resistance is too high in the test process. At this time, the rust should be removed first. If it still cannot be eliminated, use the resistance file of the multimeter to check the conduction of the test line.

5. In the detection of high-rise buildings, because the line is too long and too thick, resulting in the increase of the line resistance and induced voltage, resulting in measurement error, the conductor with low wire resistance should be used to minimize the measurement error.

6. When there are cushion soil, sand, stone and other materials in the measured area, the measurement error is caused by the difference of resistivity of the upper and lower layers of soil. At this time, a deep iron drill should be conducted to make it fully contact with the soil under the cushion or avoid the soil layer, so as to reduce the measurement error.

7. When the detected grounding device is embedded in a complex structure, it may change the current direction of each pole of the measuring instrument, resulting in poor or unstable measurement; At this point, understand the layout of the grounding device and choose a place with less impact for measurement.

8. Due to the influence of surface potential difference or strong magnetic field, the measurement results are not accurate. At this time, it should be as far as possible from the large potential difference or strong magnetic field.

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