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Leakage current measurement

time:2021/2/6   source:华天电力  reading:302 time

Insulation resistance tester has leakage current measurement

The wiring and principle of the DC leakage current test and the DC withstand voltage test are the same, and they are carried out simultaneously. The principle of leakage current measurement and insulation resistance measurement is basically the same. The difference is that the power supply used to measure the leakage current generally adopts an adjustable DC high voltage device. , And use a microammeter to directly measure the current flowing through the sample. The leakage current measurement has the following advantages compared with the insulation resistance measurement:

Insulation Resistance Tester (3).png

1. The test voltage is high and can be adjusted at will. The corresponding DC test voltage is applied according to the different voltage levels of the tested product. This voltage is much higher than the voltage of the megohmmeter. For example, 40kV is required for the primary winding of a 110kV transformer. DC high voltage, so it is easier to find certain insulation defects (such as porcelain insulation cracks, local damage, insulation oil deterioration, insulation along the surface carbonization, etc.) than measuring the insulation resistance with a megger.

2 Use a microammeter to monitor the leakage current, with high sensitivity, and the comparison can be repeated many times.

3. The insulation resistance value can be converted according to the measured value of the leakage current, while the insulation resistance value measured by the megohmmeter generally cannot be converted into the leakage current value. This is because according to the load characteristics of the megohmmeter, the output of the megohmmeter The terminal voltage is related to the insulation resistance value of the tested product, not necessarily the standard voltage of the megohmmeter nameplate.

4. In the leakage current test, the relationship curve between the leakage current and the pressure time and the relationship curve between the leakage current and the applied voltage can be drawn, and the insulation status can be judged through these curves.

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