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Preparation work before megger measurement

time:2021/1/24   source:华天电力  reading:239 time

Insulation resistance meter is also abbreviated as megohmmeter. Nowadays, digital megohmmeter is commonly used. It is a common instrument for testing insulation resistance in electrical installation and maintenance work. Digital megohmmeter measuring insulation resistance requires the following preparations to ensure the safety of the digital megohmmeter and the accuracy of the test results.


Although the digital megohmmeter is already a relatively simple and convenient insulation resistance tester, the work that needs to be prepared before the digital megohmmeter is as follows:


Before measurement, it is necessary to check whether the measured object is connected to the power source. When the measured object is connected to the power source, it should be withdrawn from the running state and cut off the power supply before the measurement. The measured object cannot be tested with power, otherwise the insulation resistance cannot be measured. It will also damage the digital megohmmeter and cause personal electric shock and other accidents.


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The equipment under test must be fully discharged before the measurement. For the object under test after the power is disconnected, the test point should be short-circuited between the tested points or to the ground to fully discharge. Especially for equipment containing capacitors and equipment with large capacitance, such as large motors, long cables, large-capacity transformers, etc., the discharge time needs to be longer, usually two to three minutes, and the test should be tested if necessary The measured points and related parts of the object are short-circuited for a period of time and then reopened, and then short-circuited after a period of time. Repeat this several times until it is confirmed that there is no residual charge before measurement.


Possible influencing factors need to be eliminated before digital megohmmeter measurement


Although some measured objects are not directly related to the power supply, if there are high-voltage, high-current conductors or radiating electromagnetic field signals inside or near it, such influencing factors must also be eliminated. In short, the insulation resistance can be measured only when the object to be tested is not charged and cannot be induced by other power sources, so as to ensure the safety of personnel and the digital megohmmeter and the accuracy of the test results.


Clean the tested equipment before measurement. In order to ensure the accuracy of the test results, the measurement part of the tested object must be cleaned. For example, the vicinity of the tested point and the surface of the tested object should be wiped clean without dirt or Water vapor, so as not to affect the accuracy of the measurement due to its leakage factors.


For the test points connected to the test line on the test object, it is also required to be clean and clean. Dust, oil and rust should be eliminated, contact resistance should be reduced, and electrical contact reliability should be ensured.

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