Generally, there are three types of electrodes of a withstand voltage tester, namely, semisphere, mushroom and flat.
Experiments have proved that the same oil sample uses three different shapes of electrodes under the same conditions, and the measurement results are different. Generally, the measured dielectric strength value of the mushroom electrode is the highest, followed by the semisphere shape, and the flat plate shape is the lowest. When the breakdown voltage of the oil is above 30kV, if the test value of the flat electrode is the standard, the mushroom electrode is roughly 4-6kV higher, and the semisphere cap shape is roughly 1-2kV higher. For example, when the breakdown voltage of oil is below 30kV, the above difference tends to be shortened or is basically the same. The use of Semisphere electrodes or Mushrrom shaped electrodes is more popular in current electric fields.
In order to ensure safety, both new oil and purified oil should be tested for dielectric strength before use. Oils in operation should also be tested regularly for their dielectric strength. Only those that meet the requirements of national standards can be used. This measurement is taken 3 to 6 times in the sam sample of oil, and we take the average value of these readings. . Portable transformer oil tester is required at site to perform the regular testing before filling new transformer oil into power transformers, or judge the effect of transformer oil filtration.
If the test BDV value is below the required value, vacuum dehydration & filtration plant is needed to remove moisture, gases and solid particles, mechanical impurities, as well as acids and other oxides. Thereby improving the dielectric strength of transformer oil. When the oil bdv test result is ok, and only need to filter it before filling into power transformers, the portable oil transfer unit can be used to realize this function.
PureTech is a manufacturer specialized in oil filtration, oil regeneration, oil testing, and waste oil recycling, if you have any problems in oil treatment, please contact us for support.
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