First, the ground resistance is detected incorrectly or indicates the cause of instability or even negative values

As the grounding resistance detection device is composed of many complex electronic components, the detection line is long. Under the influence of harsh environment and operation, measurement errors are often caused. It is difficult to determine the exact value of the measured ground resistance.

Cause analysis,

(1) large potentiometers are stored on the ground and have independent grounding in many places. For example, transformers are grounded in factories and complex buildings. Due to various reasons, the grounding resistance increases, the insulation of the transformer itself deteriorates, and leaks occur. Potential difference will be generated around the grounding electrode. If the detection rod is placed around the grounding electrode, the measurement accuracy will be affected.

(2) the grounding electrode itself is provided with alternating current (poor insulation of the electrical equipment, leakage caused by local short circuit and high-voltage power supply near the lead line); The previous structure of the building was puzzling. The wiring is disordered, sometimes even the zero line potential difference is more than 100V, which directly affects 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 protective devices, resulting in time-sharing phenomenon; Detection rods and crocodiles are used for a long time and have oxidative corrosion, which may also lead to poor contact. If the grounding electrode is heavily oxidized, the reading may be affected.