Megohm meter is a relatively common measuring instrument, mainly used to check the insulation resistance of electrical equipment, household appliances or electrical lines to ground and phase, the function is to ensure that the equipment, electrical appliances and lines work in normal state, to avoid electric shock casualties and equipment damage accidents. The following are three misunderstandings about megohmmeter usage summarized by Xinsheng neng.
Myth1:
The rated voltage of the insulated megohmmeter is not suitable for the voltage of the electrical equipment under test. That is, different megohm meters should be used for testing transformer high voltage and low voltage coils. 2kV AC was applied to the insulation of 0.4kV side coil as the voltage withstand test, and there was no breakdown, flashover and other abnormal situations within 60s, while 42kV AC was applied as the voltage withstand test for 10kV. Therefore, the insulation resistance of high voltage to low voltage, high voltage to earth and iron core to earth should be measured with a megohm meter with a range of more than 2500M ω. The low voltage on the 0.4kV side can only use a 500V or 1000V megohmmeter to ground. If a 500V and 1000V megohmmeter is used to measure the high voltage side with rated voltage higher than 500V and 1000V, the measurement result will be incorrect. Measuring the insulation resistance on the low voltage side with a megohmmeter with a high rated voltage may destroy the insulation.
Myth 2:
The measurement method of two people working together is not adopted." After reading the above values, the subject should be disconnected without stopping the handle rotation, and then the rotation can be stopped to prevent damage to the megohm meter due to charge feedback discharge accumulated by the capacitor of the sample. This is a common method of use in the general instruction manual or teaching materials, but quite a lot of testers shake after wiring, so many megohmmeter components are damaged, or use once or twice will cause the megohmmeter scrap and repair. When we use the megoh meter, two people are used to measure. After connecting the test line, one person is responsible for turning the megoh meter handle and reading, and the other person holds the test end in hand and follows the command of the operator who turns the megoh meter handle. Lap test, pull, discharge "password.
Myth 3:
The use of general yarn, glue yarn instead of megohm table line, this is very non-standard practice. Because the insulation value of general yarn and glue yarn is far lower than the special test line. The insulation value of the special test line will not be affected by the lap of the end of the hand. On the contrary, the operator may be injured when the general yarn and glue yarn are shaken. At the same time, the special test line should be properly kept.
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