It is vented at the top above the main tank and bushings and generally half-filled with the transformer oil to allow expansion and contraction due to change in temperature of the core and winding of the transformer.
Its main function is to provide the extra space for the expansion and contraction of the transformer oil due to variation in the temperature of the winding of the transformer.
Function of Conservator Tank of Transformer
The main function of conservator tank is to maintain the oil level in the main tank by entering the extended insulating oil into the it. When the transformer is over-loaded or other faults occurs due to which winding generates heat that increases the temperature of the insulating oil.
Then, the volume of insulating oil inside main tank of transformer increases and conservator tank provide sufficient space for the expanded insulating oil. It also acts as a reservoir for the insulating oil.
Construction of Conservator Tank of Transformer
Conservator tank is a cylindrical shaped oil container made up of iron closed from both ends. The tank is cylindrical to provide sufficient space for the expansion and contraction of the transformer oil. One large inspection cover is provided on either side of the container to facilitate maintenance and cleaning easily from inside of it.
A pipe that comes from main tank is projected inside the conservator tank from bottom portion allowing insulating oil to flow between them. Head of the pipe inside it is provided with a cap because this cap prevent oil sludge and sediment to enter into main tank from it.
A buchholz relay is also mounted on the pipe which connect it to the main tank to protect the transformer from the all kinds of internal faults that generates heat.
Generally, a silica-gel breather is mounted on the pipe enters into the conservator from top portion. If it enters from bottom, it should be projected well above the level of oil inside it. This arrangement ensure that insulating oil does not enter into the silica-gel breather even at highest operating level of insulating oil.
The silica-gel breather is fitted to absorb moisture from the air that enters the tank as the oil contracts. A MOG (Magnetic Oil Gauge) is also installed at the lower half to check the level of the insulating oil inside it. Some conservator designs have a air cell made of flexible material like Nitrile butadiene rubber (NBR) which expands and deflates to accommodate oil volume changes preventing direct contact between the oil and the silica-gel breather.
Working principle of Conservator Tank of Transformer
When the transformer is over-load or other faults occurs that causes generation of heat in winding and core due to which temperature of insulating oil increases. Then the insulating oil expand and its volume also increases.
Then, the extended volume of the insulating oil moves upward into the conservator to occupy the vacant space above the oil level inside it which is partially occupied by the insulating oil. Consequently, corresponding quantity of air of that space is pushed outside through the silica-gel breather.
On other hand when the load of transformer decreases or transformer is turned off then, the heat generation stops and temperature of insulating oil also decreases, the oil inside the main tank contracts. Then, the oil moves downward from conservator tank to main tank and corresponding quantity of the atmospheric air enters into the conservator through silica-gel breather.
Benefit of Conservator Tank
- Maintains Insulating Oil Level
- Prevents Overheating
- Maintains Insulating Oil Quality
- Ensures Safety
Types of Conservator Tank
There are mainly two types of conservator tank which are listed below.
- Atmo-seal Type Conservator Tank
- Diaphragm sealed Conservator Tank
Conclusion
Hope, you have clearly understand about the conservator tank of the transformer, its function, construction, working principle, benefits and types. Make sure to leave your opinion and suggestion about this post in the comment section below.