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Insulation resistance test

time:2021/9/17   source:华天电力  reading:253 time

Insulation resistance test


To check the insulation status of electrical equipment, measuring the insulation resistance is the easiest auxiliary method. This is a very common test. Nowadays, a megohmmeter is generally used to measure the insulation resistance and absorption ratio. Common tools are megger and insulation resistance tester. The more advanced ones are adjustable high-voltage digital megohmmeters and intelligent insulation resistance testers.


Insulation Resistance Tester (3).png


1. Why should insulation resistance be measured


The function of the insulator is to isolate electricity. Including the isolation between phase wires (phase-to-phase insulation) and the isolation between phase wires (insulation to ground). The insulation requirement of electrical equipment is non-conductivity, which requires a relatively high degree of insulation resistance. For any kind of electrical equipment. Ensuring that it has a sufficiently high degree of insulation resistance between phases and the ground is one of the important indicators for the safe operation of electrical equipment. Therefore, measuring the insulation resistance of electrical equipment is a very important process.


2. Aging of insulation resistance


In the process of long-term operation, electrical equipment is inevitably subject to internal electric, thermal and mechanical forces, as well as external atmosphere (such as rain, fog, thunder and lightning, etc.), environmental, and external forces. These factors may cause the aging of the insulation resistance of electrical equipment and reduce the electrical insulation capability of electrical equipment. The continuous reduction of the insulation capacity will eventually lead to the complete destruction of the insulation. Therefore, regular measurement of the insulation resistance and timely investigation of the factors causing the loss of the insulation resistance are important guarantees for the safe operation of electrical equipment.


Three, the effect and shortcomings of measuring insulation resistance


Through the measurement of the insulation resistance of electrical equipment, it can effectively reflect defects such as the overall dampness of the equipment insulation, the penetrating channels in the insulation, the deterioration of the insulating oil, the dampness of the equipment water insulation, and the cracks of the insulating porcelain sleeve.


However, in some cases, although there are some local defects in the insulation (such as partial discharge), the phase-to-phase insulation and the relative-to-earth insulation are still maintained well, and the insulation resistance is rarely reduced or even lost. The measurement of the insulation resistance cannot be found and judged. This type of defect needs to be detected by other test items. Such as partial discharge test with partial discharge detector, partial discharge monitoring system, etc.


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