In most cases, partial discharge always occurs at high voltage, so the transformer test standard stipulates that the calibration value on the terminal should be taken as the apparent discharge amount, that is, the effect of discharge at all different parts should be converted into the change of charge on the terminal.
The measurement of electrostatic discharge caused by electrified oil flow in transformer is different from this. The form, location and cause of electrostatic discharge have certain randomness. Although the usual partial discharge test circuit can be used for measurement, the discharge can not be calibrated. DC electrostatic discharge is a single discharge pulse, which has a large discharge energy. Therefore, the sensitivity of the current partial discharge measuring instrument is sufficient. It can be qualitatively judged by observing the amplitude and number of discharge pulses.
The temperature of transformer oil and the velocity of oil flow are very important factors affecting the electrification of oil flow. At the same time, the inner wall paint of transformer is blue, and a lot of red paint is falling off inside the radiator. These impurities contaminate oil, on the one hand, increase the loss factor of oil medium, on the other hand, the change of oil quality increases the charged degree of oil. The electrostatic discharge occurs when the local flow rate is too high, which is faster than the discharge rate. Because there are many factors affecting the electrification of oil flow, the combination of many factors will lead to the generation of electrification of oil flow.
With the continuous expansion of the power grid, the demand for transformers is increasing, and the demand for matching transformer oil is also increasing. The main raw materials for transformer oil production are naphthenic and paraffin-based crude oil. However, naphthenic crude oil is a rare resource in the world, accounting for only about 2% of the total crude oil.
At the same time, the manufacturers and users of transformer oil have some doubts about paraffin-based and naphthenic transformer oil. Kaio transformer oil analyses the composition of the two kinds of crude oil:
The composition of the two transformer oils was analyzed by mass spectrometer. The results of mass spectrometry analysis showed that the aromatics content of paraffin-based transformer oils and naphthenic transformer oils were similar. The main difference was that the paraffin-based transformer oils had higher alkanes content, while naphthenic oils had higher naphthenic hydrocarbons content, especially tricyclic and tetracyclic naphthenes.