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Principle of Insulation Resistance Test

time:2020/12/3   source:华天电力  reading:308 time

Insulation resistance refers to the resistance between two parts of conductors separated by insulating materials, and the insulation resistance tester is an instrument used to measure the insulation resistance. In order to ensure the safety of electrical equipment operation, it should be handled with different polarities (different phases). The insulation resistance between the conductors or between the conductor and the shell puts forward a low requirement. The electrical equipment produced by it must be tested under a certain voltage before leaving the factory to ensure the normal operation of the equipment and the personal safety of the personnel using the equipment.


Many electrical equipment must be regularly tested for insulation resistance during use. For example, during the yellow plum season and thunderstorm weather each year, various electrical equipment of various enterprises, especially high-voltage equipment, will have varying degrees of moisture or partial damage, which will cause electrical damage. The insulation resistance of the equipment is reduced, which directly threatens the safe operation of electrical equipment and the personal safety of staff. In order to prevent accidents, various preventive tests must be carried out on electrical equipment regularly. Another example is the safety requirements of household appliances: basic The insulation is 2MQ, and the reinforced insulation is 7MQ, which is for the normal operation of electrical equipment and the personal safety of staff.


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Therefore, it is particularly important to understand the insulation characteristics of the equipment. The factors that affect the measured value of the insulation resistance are: temperature, humidity, measurement voltage and operating time, residual charge in the winding and the surface condition of the insulation, etc., by measuring the insulation resistance of electrical equipment, The following objectives can be achieved:


(1) Understand the insulation performance of the insulation structure. A reasonable insulation structure (or insulation system) composed of insulating materials should have good insulation performance and high insulation resistance.


(2) Understand the insulation treatment quality of electrical products. If the insulation treatment of electrical products is poor, the insulation performance will be significantly reduced.


(3) Understand the damp and contaminated insulation. When the insulation of electrical equipment is damp and contaminated, the insulation resistance will usually decrease significantly.


(4) Check whether the insulation can withstand the withstand voltage test. If the withstand voltage test is performed when the insulation resistance of the electrical equipment is lower than a certain limit, a larger test current will be generated, causing thermal breakdown and damaging the insulation of the electrical equipment Therefore, usually various test standards stipulate that the insulation resistance should be measured before the withstand voltage test.


It can be seen that the size of the insulation resistance can often sensitively reflect the insulation situation, and can effectively discover the general moisture, local severe moisture and penetration defects of the equipment. Therefore, measuring the insulation resistance is one of the important means to understand the insulation of the equipment, and it is insulation prevention. An indispensable item in the sex test.


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