Megger use and safety precautions - Solutions - Huaqiang Electronic Network

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It should also be noted when using a megohmmeter that some megohmmeters have a scale value that does not start from zero, but starts at 1 MΩ or 2 MΩ. This megger is not suitable for measuring the insulation resistance of low-voltage electrical equipment in wet environments, because the electrical equipment's insulation resistance is less than 1MΩ, the correct reading will not be obtained.
1. When using the megohmmeter, it should be placed smoothly to avoid shaking the handle of the generator, and the body shakes to affect the reading. For a level-adjusted megohmmeter, first adjust the horizontal position.
2. The measuring line dedicated to the meter, or two single-core multi-strand flexible cords with high insulation strength should be used, and the stranded insulated cord should not be used.
3. Before the measurement, the open circuit test and short circuit test shall be carried out on the megger. Immediately open the "L" and "E" terminals, shake the handle of the generator to the rated speed, the pointer should be in the "∞" position; then short the "L" and "E" to shake the handle, then the pointer should be "0" position.
4. The electrical equipment under test must be disconnected from the power supply. It is forbidden to approach the device under test during the measurement.
5. The device under test must be short-circuited to ground before measurement, especially for capacitive electrical equipment such as cables, large-capacity motors, transformers, and capacitors. If it is not discharged, an electric shock may occur.
6. When wiring, the “E” terminal should be connected to the electrical equipment casing or ground, and “L” should be connected to the conductor under test. When measuring the insulation resistance of the cable, connect the insulation of the cable to the “G” terminal. If the insulation resistance of the device is measured in wet weather, the shield terminal should also be used to connect it to the insulation support to eliminate the effect of leakage current on the surface of the insulation on the measured insulation resistance.
7. Before measuring, you should first understand the surrounding temperature and humidity, and record it during measurement to facilitate the analysis of the insulation resistance afterwards.
8. When measuring, the instrument should be placed away from the conductor carrying large current and the place with external magnetic field, so as not to affect the measurement results.
9. When measuring, shake the handle clockwise, so that the megger should maintain the rated speed, generally 120 r / min. When the measured object has a large capacitance, in order to avoid the pointer swing, the rotation speed can be appropriately increased.
10. When measuring capacitors, cables, large-capacity transformers and motors, it is necessary to have a certain charging time. The larger the capacitance, the longer the charging time is. Generally, the reading after 1 minute of megohmmeter rotation is subject to the reading.
11. After measuring the insulation resistance of the capacitive electrical equipment, discharge the electrical equipment under test to avoid danger.
12. Double-circuit overhead lines and busbars that cannot be completely de-energized are not allowed to be measured when the induced voltage of the circuit under test exceeds 12 V, or when overhead lines during lightning storms and electrical equipment connected to overhead lines are used.
13. Before measuring, wipe the surface of the device under test to avoid leakage affecting the measurement results.
14. Do not touch the measuring part and the megohmmeter terminal by hand until the megohmmeter stops shaking and the equipment is not discharged to avoid electric shock.