First, the cause of inaccurate grounding resistance detection or unstable indication or even negative value
Because the grounding resistance detector is composed of many sophisticated electronic components, it has a long detection line. Under the influence of bad environment and operation, it often causes measurement error. It is difficult to confirm the accurate value of the measured grounding resistance. factor:
(1) The large potential table is stored at the surface, and there are independent grounding in many places. For example, the transformer is grounded in factories and complex buildings. Due to various reasons, the grounding resistance is increased, the insulation of the transformer itself is deteriorated, and leakage occurs. A potential difference is generated around the ground electrode, and if the detection rod is placed around it, the measurement accuracy will be affected.
(2) The grounding electrode itself has alternating current (the insulation of the electrical equipment is not good, the leakage caused by partial short circuit, and the high-voltage power supply in the vicinity of the down-conductor line); the previous structure of the building was confusing. Wiring is disorderly, and sometimes even the zero line potential difference is above 100V, which directly affects the measurement error of the grounding resistance.
(3) Poor contact (including the instrument itself): The grounding resistance tester wiring connection is easy to break due to frequent bending, and it is difficult to find due to the existence of the protective cover, causing the phenomenon of time-breaking; The detection rod and the crocodile are used for a long time, and there is oxidative corrosion, which may also cause poor contact; if the grounding electrode is seriously oxidized, the measurement reading may be affected.
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