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Insulation resistance test related issues

time:2021/1/8   source:华天电力  reading:262 time

One. Why is megohmmeter widely used in insulation testing of high voltage electrical equipment?


The size of 

the insulation resistance value can effectively reflect the overall dampness, contamination, and serious overheating and aging of the insulation, and the measurement of insulation resistance with a megohmmeter is simple, safe, clear in concept, and inexpensive. When the equipment is insulated, there are the following obvious disadvantages:


(1) The megohmmeter is widely used in the general DC mega-edge test.


However, the voltage of the ohmmeter tested with a megohmmeter is below 2.5KV, which is much lower than the working voltage of some electrical equipment. When the equipment has certain defects, the leakage current under high voltage is much larger than that under low voltage. That is, the insulation resistance under high voltage is much smaller than that under low voltage.


Insulation Resistance Tester

(2) The output current of a general DC megohmmeter is below 2mA. When the equivalent capacitance of the tested equipment is large (such as power transformers, generators), the charging speed is slow, and it is difficult to obtain accurate data.


 2. What effect does temperature have on the insulation resistance value? How to equal the insulation resistance value of the same test product under different temperature environments?


The built-in CPU of the high-voltage insulation tester can automatically convert the insulation resistance to the value under the standard temperature according to different ambient temperatures.


3. Why do some electrical equipment need to test the insulation resistance and the polarization curve?


Measuring insulation resistance is one of the easy ways to understand the insulation of electrical equipment. Large-capacity samples can more accurately reflect the insulation of the sample by measuring the absorption ratio and polarization index, but the polarization curve is the curve of the relative value of the insulation resistance over time, which can more accurately reflect the insulation of the sample. Therefore, For some large-capacity samples, the insulation resistance must be tested, as well as the polarization curve.

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