How do we fill our HV power transformers? Do we know how to do it the right way?
According to the rules of the art, the procedure to follow for oil-filling HV power transformers is to do so while applying vacuum to the main tank. This minimizes the chances of moisture contaminating the solid insulation of the active part.
As part of this process, some components of the transformer that are not suitable for withstanding vacuum, such as radiators, the OLTC, and in some cases, the conservator, must be isolated from the vacuum circuit. For radiators, it is enough to close the valves that connect them to the main tank. In the case of the OLTC, it is possible to equalize pressures between the OLTC oil compartment and the main tank. But we need to work out these questions that: what about the conservator? Do we know in all cases whether the auxiliary tank is suitable (or not) to withstand a vacuum? Is it reinforced properly? Are we sure? How could we identify it?
The magnitude and effects of the internal pressures that result from the application of vacuum on a surface that is not prepared to withstand it can be clearly identified. In addition, we should also pay attention to the following points.
1) Designers must put critical operational instructions on caution plates mounted on transformers, preferably near to rating plates. Buyers must insist on such data during the drawing approval stages. Valve diagram plate, airbag activation instructions, disposal plate, impedance at extreme taps, etc, etc.
2) Field staff must watch the transformer tank and external parts during the initial stages of the vacuuming process for any excessive deflection or abnormal sound. Stop the process before a calamity.
3) A much more important caution, not mentioned in the post- before starting a vacuum, first check leak tightness. With a leaky transformer, you will be allowing moist outside air to seep in through leaks, while you think you are keeping a vacuum inside the tank.
Wuhan Huayi Electric's Double Stage Vacuum Transformer Oil Purifier is used for the maintenance of large-scale power substation transformers, rapitd and deep treatment of new transformer oil, important insulation oil, as well as vacuum filtering and purifying of mutual inductor oil, capacitor oil, refrigerator oil.