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Ground resistance detector reading

time:2020/5/28   source:华天电力  reading:608 time

The cause of inaccurate ground resistance detection or unstable or even negative indicator value

As the ground resistance tester is composed of many precision electronic components, the detection line is long, and measurement errors often occur under harsh environment and operating conditions. It is difficult to determine the exact value of the ground resistance to be measured. The main reasons are as follows:

(1) there are large potentiometers at the surface, and there are independent grounding in many places. If the transformer in the factory or the complex building is grounded, due to various reasons, the grounding resistance increases and the insulation of the transformer itself is poor, resulting in the phenomenon of electricity leakage. The potential difference is generated around the grounding electrode. If the detection rod is placed around it, the measurement accuracy will be affected.

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(2) the measured grounding pole itself has alternating current (poor insulation of electrical equipment, leakage phenomenon caused by partial short circuit, interference of combined high-voltage power supply near the lead line). The previous early building structure is more chaotic, the wiring is disorderly, sometimes even the ground zero line potential difference in 100V voltage above, directly affect the measurement error of the ground resistance.

(3) poor contact (including the instrument itself), the connection of the ground resistance tester is easily broken due to frequent bending, and it is difficult to find due to the existence of the protective sleeve, resulting in the phenomenon of on-off and on-off. In addition, due to the detection stick and crocodile and use for a long time, there is oxidation corrosion phenomenon, can also cause bad contact. If the measured grounding electrode oxidation serious to embroidery is not good, it will also affect the measurement reading.

(4) there are strong electromagnetic fields emitted by transmitters and antennas nearby. In the vicinity of the high-power transmission base, such as mobile, microwave, BP and other communication stations, high-voltage substation and high-voltage lines, high-power equipment frequently started.

(5) when the grounding device and metal pipe are buried in a complex ground, it may also cause poor or unstable ground resistance measurement. For example, in gas stations and chemical plants, due to the complex underground metal pipeline layout and the presence of underground metal appearance, the current direction at each end of the measuring instrument changes according to the normal detection wiring, often resulting in the phenomenon that the measuring value is zero or negative. This can also occur if the soil resistivity of the same site is different.

(6) when tall buildings are detected, the detection error is caused by the voltage caused by the excessively long detection line, and the long line itself also has the line resistance.

(7) when sandy soil with high soil resistivity and poor water absorption is used as the whole layer of building foundation cushion, the measured ground resistance is often too large.

(8) if the operation is not carried out in accordance with the method specified in the manual, and the instrument itself is not properly maintained, the instrument with disease and checked shall be used.

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