G3B breathing buffer box for sealing open-type transformers
The G3B is a breathing buffer box for sealing, including retrofit sealing, of open-type power transformers with a conservator. It shields the oil from atmospheric oxygen while keeping the gas protection function.
- Principle
- oil seal with floating aluminium discs (diffusion barrier)
- Oil temperature compensation
- up to 30 °C
- Gas release
- when atmospheric pressure is exceeded by 40 mbar
- Make-up
- at a vacuum of 20 mbar, with dry air (G3B) or nitrogen from a cylinder (G3B/N2)
Price, availability and lead time on request. We help with analogue selection, customs clearance and delivery.
Description
Oxygen dissolved in the oil accelerates ageing of the insulation system and is considered one of the main causes of shortened transformer service life. In an open transformer the consumed oxygen is constantly replenished from the atmosphere. Units protected from air keep the properties of the solid insulation and the oil for longer, so sealing is increasingly ordered for both new and existing transformers.
The usual alternative is an elastic diaphragm (hydro-compensator) in the conservator. The manufacturer lists its drawbacks. It is expensive, the membrane ages faster than the transformer (by operators' estimates, at least three replacements over the service life), it does not remove moisture, the Buchholz relay function is weakened by degassed oil, and the condition of the diaphragm is hard to monitor. The G3B has none of these drawbacks. In the natural variant, oxygen consumed by the ageing of the active part is gradually replaced by air, and the final state of the oil is strongly depleted of oxygen.
The box is cylindrical and is built into the breathing line of the transformer directly before the air dehydrator. Inside is an inner cylinder without a bottom, partly filled with oil. This oil serves as the working medium for the pressure change and as a diffusion barrier. Floating aluminium discs separate it from the air, dividing the oxygen-depleted gas in the conservator from the dry outside air. Two natural end positions of the oil level compensate temperature fluctuations of the oil in the tank of up to 30 °C. When the pressure in the conservator exceeds atmospheric by 40 mbar, gas is released outside. At a vacuum of 20 mbar the box supplies dry air (natural sealing G3B) or nitrogen from a cylinder (G3B/N2). The nitrogen variant brings the oil to a low-oxygen state faster, because nitrogen is also metered in during cooling.
The barrier also retains the sparingly soluble fault gases (H2, CO), so diagnostics by dissolved gas in oil gives a more reliable result. The G3B is installed without interfering with the oil system. The box stands near the ground, which is convenient for small transformers in hard-to-reach places, and it is easy to inspect and maintain. After a transformer is replaced, the box can be reinstalled on another unit. The manufacturer offers several G3B versions and options for placing it beside the transformer.
Technical specifications
| Principle | oil seal with floating aluminium discs (diffusion barrier) |
|---|---|
| Oil temperature compensation | up to 30 °C |
| Gas release | when atmospheric pressure is exceeded by 40 mbar |
| Make-up | at a vacuum of 20 mbar, with dry air (G3B) or nitrogen from a cylinder (G3B/N2) |
| Installation | in the breathing line before the air dehydrator, near the ground |
| Mounting | without interfering with the oil system |
Replacement for
no direct analogue; the closest are film/nitrogen oil protection (general type)
selected by purpose and main parameters, please confirm with our manager
Request a price and lead time
G3B breathing buffer box for sealing open-type transformers. We reply within one business day.
Or email sales@usk.ua or call 044 339-50-20.
Customs codes
| UKTZED (Ukraine) | 8504 90 99 00 |
|---|---|
| HS, 6 digits | 8504 90 |
| CN (EU) | 8504 90 99 |
| HTSUS (USA) | 8504 90 96 90 |
| China customs tariff | 8504 90 90 00 |
Codes are for reference: the final code is determined at declaration for the specific model.
Questions and answers
At what pressure differences does the G3B operate?
Gas is released outside when the pressure in the conservator exceeds atmospheric by 40 mbar. At a vacuum of 20 mbar the box supplies dry air or nitrogen from a cylinder.
Is it necessary to interfere with the oil system during installation?
No, the G3B is built into the breathing line before the air dehydrator without interfering with the oil system. The box is installed near the ground.
How does the G3B differ from an elastic diaphragm in the conservator?
The box keeps the Buchholz relay function and retains the sparingly soluble fault gases H2 and CO. After a transformer is replaced it can be reused.
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