Transformer oil get contaminated during process. During usage transformer oil absorbs moisture, dirty particles. Which needed to be removed from transformer oil as Transformer oil efficiency get reduced due to moisture and other contaminations.
Transformer oil filtration process is used to remove the moisture from oil so to dehydrate the oil and remove unwanted solid particles.
Also degassing is done in transformer so to maintain transformer oil level.
For Transformer technical specifications visit link:-http://electrialstandards.blogspot.com/2015/10/transformer-technical-specifications.html
Oil filtration enhances transformer life.
Advantages of Transformer oil filtration
Below are the listed some advantages of transformer oil filtration:-
1. Oil filtration will improve better insulation of Transformer winding as Transformer oil is used for both transformer cooling as well as insulation.
2. Oil filtration will improve insulating media such as Paper, cellulose used in transformer.
3. Oil filtration increase life if transformer as 70% transformer breakdown occurs due to transformer oil contamination.
If Transformer oil filtration doesn’t done then following problems may occur in transformers:-
1. Overheating of transformer oil and may leads to burning of Transformer.
2. Corona discharges in Transformer
3. Arcing in Transformers
So it is always important to maintain transformer oil Dielectric Strength.
There are three processes for Transformer oil Treatment:-
3. Degassing and dehydration
In first step Transformer oil temperature is raises to raised to 65 degree Celsius. At this temperature moisture and gases get separated from oil in degassing chamber. At this temperature viscosity of Transformer oil drops which will leads to better filtration.
In this process sludge and dirt are removed from Transformer oil. There are two methods for removing the sludge and dirt from Transformer oil, these are:-
(i) Removal of Sludge and dirt by using filter candles and
(ii) Removal of Sludge and dirt by means centrifugal action.
Now let’s discuss about these two methods:-
(i) Removal of Sludge and dirt by using filter candles
In this method of filtration , filtration can be done by two methods:-
(a) By using edge filter known as classical edge filter method
(b) By using depth filter method also known as filter cartridge method
(a) In edge filtration method has following advantages:-
1. Filter can be cleaned and reused for several times.
2. It can handle large quantity of sludge
Disadvantages of edge filtration method:-
1. Cleaning of edge filter requires lot of time and effort.
2. Reinstallation of edge filter requires lot of time and effort.
In edge filtration, filter is cleaned by using reverse pressurized flow of dry air or nitrogen. After cleaning it is dried in bright sunlight. Reinstallation, cleaning, drying is effort taking and time consuming and also required special skills for the same.
(b) Filter cartridge method:-
Now days this method is used and cartridges used in this method are very much similar to those of the water filter cartridges. There are so many verities of purification ranges depending upon cartridge openings i.e. from 500 micron to 0.5 micron size.
There are certain advantages of using filter cartridges over edge filtration method:-
(i) Ease of replacement
(ii) Ease of availability
(iii) No moisture as filter used is non-hygroscopic but edge filtration method filters are hygroscopic.
(ii) Centrifuging action for removal of sludge.
Centrifugal action as everyone knows that in centrifugal action heavy particles automatically get accumulated at bottom by centrifugal force and liquid from which particles to be removed is get separated. In Transformer oil cleaning Centrifuges are used in shape of cone which are used to separate sludge and particles from Transformer oil. It is very slow process if we don’t use motor to spin centrifuge cone at high speed. By this method we can’t able to remove dirt which have sizes less than 10 micron level.
To remove this limitation of centrifugal action a power driven centrifuge is uses. Although it is very costly method but it has main advantage is that it doesn’t require changing of filter elements. There is one limitation of this method is that it can remove un-dissolved water from the oil but it can’t remove dissolved moisture from oil.
3. Degassing and Dehydration of Transformer oil
In last step of Transformer Oil filtration dehydration and degasification of oil is done. This process takes place in degassing chamber. This process is possible in vacuum as there is difference in boiling point of water, gas and Transformer oil. In gas separation process it is very important to retain the ar hydrocarbons so as to retain oil properties. Water is removed by either centrifugal action or by usinf coalescing action.
This is how oil filtration takes place in Transformer oil.