Use and safety precautions of megohmmeter

Release time:

2023-02-16 09:37

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Core tip: When selecting a megohmmeter, you should also note that the scale value of some megohmmeters is not from zero, but from 1m ω Or 2m ω Start. This megger is not suitable for measuring the insulation resistance of low-voltage electrical equipment in a humid environment, because when the insulation resistance of electrical equipment is less than 1m ω The correct reading will not be obtained. 1. When using the megger, it should be placed stably to avoid shaking the generator handle and the meter body to affect the reading. If there is a megger with horizontal adjustment, adjust the horizontal position first.
When selecting a megohmmeter, it should also be noted that the scale value of some megohmmeters is not from zero, but from 1m ω Or 2m ω Start. This megger is not suitable for measuring the insulation resistance of low-voltage electrical equipment in a humid environment, because when the insulation resistance of electrical equipment is less than 1m ω The correct reading will not be obtained.
1. When using the megger, it should be placed stably to avoid shaking the generator handle and the meter body to affect the reading. If there is a megger with horizontal adjustment, adjust the horizontal position first.
2. The special measuring wire for the instrument or two single-core multi-stranded flexible wires with high insulation strength shall be used, and stranded insulated flexible wires shall not be used.
3. Before measurement, open circuit test and short circuit test shall be conducted with a megger. That is, open the "L" and "E" terminals, shake the generator handle to reach the rated speed, and the pointer should point to the "∞" position; Then, short "L" and "E" and shake the handle. At this point, the pointer should point to the "0" position.
4. The electrical equipment to be tested must be powered on, and others are not allowed to approach the equipment to be tested during measurement.
5. Before measurement, the measured equipment must be short-circuited to the ground, especially capacitive electrical equipment, such as cables, large-capacity motors, transformers and capacitors. If it is not discharged, electric shock may occur.
6. During wiring, the "E" end shall be connected to the electrical equipment shell or ground wire, and the "L" end shall be connected to the conductor under test. When measuring the cable insulation resistance, connect the cable insulation layer to the "G" terminal. If the insulation resistance of the equipment is measured in wet weather, shielded terminals shall also be used and connected to the insulation support to eliminate the impact of leakage current on the insulation surface on the measurement of insulation resistance.
7. Before the measurement, first understand the surrounding temperature and humidity, and make records during the measurement, so as to facilitate the analysis of insulation resistance afterwards.
8. During measurement, the place where the instrument is placed should be far away from the conductor with high current and the place with external magnetic field, so as not to affect the measurement results.
9. When measuring, shake the handle clockwise to keep the megger at the rated speed, generally 120 rpm. When the capacitance of the measured object is large, the rotating speed can be appropriately increased to avoid pointer oscillation.
10. When measuring capacitance, cable, large-capacity transformer and motor, there should be a certain charging time. The larger the capacitance, the longer the charging time. Generally, the reading after the megger rotates for 1 minute shall prevail.
11. After measuring the insulation resistance of capacitive electrical equipment, discharge the electrical equipment to avoid danger.
12. It is forbidden to measure the double-circuit overhead line and bus that cannot be completely powered off when the induced voltage of the measured line exceeds 12 V, or measure the overhead line and the electrical equipment connected to the overhead line in the thunderstorm.
13. Before measurement, the surface of the equipment to be measured should be wiped clean to avoid the impact of leakage on the measurement results.
14. Before the megger stops shaking and the equipment is not discharged, do not touch the measuring part and terminal of the megger with your hands to avoid electric shock.

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1. It is forbidden to measure the insulation resistance in lightning or near the high-voltage equipment. It can only be measured when the equipment is not live and there is no induction electricity. 2. During telemetering, no one can work on the tested equipment. 3. The megohmmeter wires should not be twisted together. They should be separated. 4. It is forbidden to touch the megger with hands before it stops rotating or before the tested equipment is discharged. Do not touch the metal part of the lead when removing the wire. 5. At the end of measurement, discharge large capacitance equipment. 6. The insulation of the measuring flexible wire led from the megger terminal should be good, and the appropriate distance should be kept between the two conductors and between the conductor and the ground to avoid affecting the measurement accuracy. 7. In order to prevent the leakage resistance on the surface of the equipment under test, when using a megger, the intermediate layer of the equipment under test (such as the inner insulation between the cable shell cores) should be connected to the protective ring.

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Core tip: When selecting a megohmmeter, you should also note that the scale value of some megohmmeters is not from zero, but from 1m ω Or 2m ω Start. This megger is not suitable for measuring the insulation resistance of low-voltage electrical equipment in a humid environment, because when the insulation resistance of electrical equipment is less than 1m ω The correct reading will not be obtained. 1. When using the megger, it should be placed stably to avoid shaking the generator handle and the meter body to affect the reading. If there is a megger with horizontal adjustment, adjust the horizontal position first. When selecting a megohmmeter, it should also be noted that the scale value of some megohmmeters is not from zero, but from 1m ω Or 2m ω Start. This megger is not suitable for measuring the insulation resistance of low-voltage electrical equipment in a humid environment, because when the insulation resistance of electrical equipment is less than 1m ω The correct reading will not be obtained. 1. When using the megger, it should be placed stably to avoid shaking the generator handle and the meter body to affect the reading. If there is a megger with horizontal adjustment, adjust the horizontal position first. 2. The special measuring wire for the instrument or two single-core multi-stranded flexible wires with high insulation strength shall be used, and stranded insulated flexible wires shall not be used. 3. Before measurement, open circuit test and short circuit test shall be conducted with a megger. That is, open the "L" and "E" terminals, shake the generator handle to reach the rated speed, and the pointer should point to the "∞" position; Then, short "L" and "E" and shake the handle. At this point, the pointer should point to the "0" position. 4. The electrical equipment to be tested must be powered on, and others are not allowed to approach the equipment to be tested during measurement. 5. Before measurement, the measured equipment must be short-circuited to the ground, especially capacitive electrical equipment, such as cables, large-capacity motors, transformers and capacitors. If it is not discharged, electric shock may occur. 6. During wiring, the "E" end shall be connected to the electrical equipment shell or ground wire, and the "L" end shall be connected to the conductor under test. When measuring the cable insulation resistance, connect the cable insulation layer to the "G" terminal. If the insulation resistance of the equipment is measured in wet weather, shielded terminals shall also be used and connected to the insulation support to eliminate the impact of leakage current on the insulation surface on the measurement of insulation resistance.