By hvhipot 
Problems related to insulation resistance test of high voltage equipment
one. Why is electricity the most widely used megger in the insulation test of high-voltage electrical equipment?
The size of the insulation resistance value can effectively reflect the overall dampness of the insulation, serious overheating and aging and other defects, and the measurement of insulation resistance with a megohmmeter is simple, safe, clear in concept, and cheap in high-voltage electrical equipment. The megohmmeter is the most widely used in the insulation test.
However, when testing insulation with a megohmmeter, there are the following obvious disadvantages:
(1) The voltage of the general DC 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.
(2) The output current of a general DC megohmmeter is below 2mA. When the equivalent capacitance of the device under test is large (such as power transformers, generators), the charging speed is slow, and it is difficult to obtain accurate data.
2. What is the effect of temperature 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 power 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 easiest and most commonly used methods to understand the insulation of electrical equipment. A large-capacity sample 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.