Silica-Gel Breather of Transformer
A silica-gel breather is the most commonly used way of filtering the moisture from the air entering the transformers during breathing process (i.e expansion and contraction of the transformer oil). It is one of the most important part of the transformer. The silica-gel is a very good absorber of moisture.
Construction of Silica-Gel Breather of Transformer
The silica-gel breather of transformer is very simple in the aspect of design and easy to install. It is a transparent cylindrical pot or tube containing fresh silica-gel through which, air is allowed to pass through the silica-gel breather during breathing period of transformer. It is a pot of silica-gel connected with conservator tank of transformer by the means of breathing pipe.
Freshly regenerated silica gel is very efficient and may dry down air to a dew point of below the temperature of -40°C. A well maintained silica gel breather will generally operate with a dew point of temperature -35°C as long as a large enough quantity of gel has been used.
There is an oil pot containing transformer oil called Oil Seal Cup just below the Silica Gel pot. The purpose of this oil seal pot is to remove the dust particles from the air entering into the silica gel breather. The dust particles get trapped in the oil of Oil Seal Cup.
Working Principle of Silica-Gel Breather in Transformer
Silica-gel is amorphous silicon dioxide in its crystal form. silica-gel crystal has tremendous capacity of absorbing moisture due to its hygroscopic nature.
When the atmospheric air passes through Silica-gel crystals in the silica-gel breather, the moisture present in the air is absorbed by these crystals. Therefore, the air that reaches to the conservator tank is quite dry and the dust particles present in the air get trapped by the transformer oil in the oil seal cup. The oil in the oil sealing cup acts as barrier between silica-gel’s crystal and air when there is no flow of air through silica-gel transformer’s breather.
When there is sufficient difference between the air inside the conservator and the outside air, the oil level in two components of the oil seal changes until the lower oil level just reaches the rim of the inverted cup, the air then moves from high pressure compartment to the low pressure compartment of the oil seal. Both of these happen when the oil acts as core filter and removes the dust from the outside air.
When there is sufficient difference between the air inside the conservator and the outside air, the oil level in two components of the oil seal changes until the lower oil level just reaches the rim of the inverted cup, the air then moves from high pressure compartment to the low pressure compartment of the oil seal. Both of these happen when the oil acts as core filter and removes the dust from the outside air.
Indication of Silica-Gel Breather
The color of good silica gel crystal is dark blue and orange but, when it absorbs moisture from the air blue silica gel turns into pink and orange turns into green colour. The changed colour of the silica gel indicates that silica gel is saturated and it should be replaced or re-activated.
Re-activation of Silica-Gel Breather
Silica-gel is reactivated by heating it at a temperature of 150°C to 200°C for two to three hours until its crystals regain their original blue or orange colour. Before filling it back into its cylindrical pot, must clean and dry all parts of the silica gel breather. Make sure that the oil level of transformer oil in the oil cup is correct. Also ensure that the breather is not choked and atmospheric air can easily enters through it.
Function of Silica-gel breather in Transformer
The main function of the silica-gel breather in transformer is to resist the impurities like moisture present in atmospheric air to enter into the main tank of the transformer in-order to keep air dry and clean.
Conclusion
Hope, you have clearly understand about the silica-gel breather of the transformer, its construction, working, indication, re-activation and function in transformer. Make sure to leave your opinion and suggestion about this post in the comment section below.