Transformer Oil Purification / Filtration Process /

Procedure

In this article you will understand

transformer oil purification

process, steps and methods

involved in oil purification process.

Transformer oil purification is a

process to remove sludge,

dissolved moisture and dissolved

gases from the oil.

Before we move to process details, Lets see why transformers need purified oil?

As discussed in details Advantages of transformer oil filtration in post why transformer oil filtration is required? Here we will see in brief advantages for transformer oil purification:

•Improved insulation properties of the oil and hence the other media like paper/cellulose insulation. •Better the insulation of transformer, longer the life of the transformer and lesser the breakdown of the transformer. •Longer the life of the transformer asset, good returns on investment of the asset. •Lesser breakdowns and failure of the transformer results in uninterrupted power supply.

For good performance of transformers we require filtration machines designed and manufactured with standards. At Transfo Tech. Engineering, we use Oil purification machines with International prescribed Standards (BIS, NEMA, IEEE, IEE, ASTM, ASME, IEC) for good performance of transformer.

Transformer Oil Purification Procedure

Transformer is one of the main asset in the electrical power industry which needs to be maintained for guaranteed uninterrupted power transmission in order to get assured revenue benefits.

Transformer life mainly depends on the quality of oil volume it contains.

Regular transformer oil filtration assures long and consistent results from the transformer.

Transformer oil purification is a process to remove sludge, dissolved moisture and dissolved gases from the oil. Transformer oil conditioning may also include to some extent improving the acidity of the oil.

A good oil purification system is able to deliver filtered oil with parameters as per the standard specification.

However, this revival of the oil by oil filtration plant to standard oil parameters is based on the quality of unprocessed oil and its initial process. In case the unprocessed oil does not match the standard oil parameters, then the effort of transformer oil filtration is all in vain. Alternate method of regeneration of transformer oil should be adopted in this case.

Here we shall look at the method of the

transformer oil filtration by vacuum type

dehydration and centrifuge type removal of solids and water separation.

Transformer oil conditioning is a stream line

oil filtration process of sludge purification,

moisture removal and gas removal.

The first step in this serial process is to raise

the oil temperature to a desired level,

generally up to 65 Deg C. This aids to give the

oil latent heat which later aids to dissociate

the moisture and gases from oil in the

degassing chamber.

Additionally the viscosity of the oil drops

which aids in better filtration to some extent.

Recommended heater design should consider

an area of heating of about 1 to 2 W/sq.cm. In

the transformer oil purification plant, the

heating system is protected against over pressure built up and excess temperature rise.

The second step of transformer oil

purification plant is removal of sludge and dirt from the transformer oil.

Two methods have been used for removal of

the sludge:

• Removal of sludge by filter candles. and/or

• Removal of sludge by centrifuging action.

Transformer oil filtration using filter

candles in the transformer oil purifier machine can further be classified as:

Filtration using the classical edge filter Filtration of transformer oil using the

depth type filter.

Both methods of cartridge type filtration

are prevalent and owe certain advantages and disadvantages.

The edge type filter system can be cleaned and be

reused for at least three to four times,

however, cleaning and fitting of the edge filters

involves considerable time and human effort.

This system is robust to handle large quantity of

sludge. Edge filters can be cleaned by reverse

pressurized dry air/nitrogen flow in order to

remove the contamination.

After de-sludging the paper stack is removed and

dried in oven/ bright sunlight and reused. This operation demands experience and skill set.

New trends and technology in the market

have driven transformer oil filter machines

to use filter cartridges instead edge type paper

stacked filters.

These cartridges are similar to those of the water

filter cartridges and can be selected from a

variety of purification range say from 500 micron to 0.5 micron size.

The advantage using these cartridges over the edge filter is: No moisture storage, since the filter media used can be non-hygroscopic. Easy to replace with less human effort and easy availability.

An alternate method used for dirt

separation from oil is centrifuge.

Routine transformer oil filtration or transformer oil

conditioning is often confused with transformer oil

centrifuging.

Transformer oil centrifuging is all together a

different technology and has a little impact on

improving the oil parameters.

Centrifuges used for separation of dirt from the

transformer oil can be slow speed type

centrifuges that do not require additional electric motor to spin the centrifuge cone at high speed.

However, the dirt separation from oil with

such centrifuging has limitations since these

centrifuges cannot remove the dirt less than 10

micron level.

Thus a power driven centrifuge becomes evitable

which scales up the cost of the oil conditioning machine.

Only advantage of the centrifuges is that the recurring

cost of changing filter elements is saved.

Power driven centrifuges can remove water from the

oil that is in free form but not the dissolved moisture.

Manufacturers of power driven centrifuge also often

do not guarantee removal of moisture to a level less

than 5 ppm

The third step in the oil filter machine is

dehydration of transformer oil and degasification of the transformer oil.

These processes of dehumidification of

transformer oil and removal of gasses are executed

in the degassing chamber. The dissolved water oil

separation or dissolved gas oil separation is

possible at reduced pressure, i.e. vacuum, due to

difference of boiling point of water, gas and

transformer oil.

In the process of separation of gases from the

oil it becomes important to retain the aromatic

hydrocarbons so that the original properties of

the oil are retained. When the water level in the oil is above

saturation level of the transformer oil, oil is

observed in free water.

Removal of free water can be done by power

driven centrifuge or by coalescing principle,

where the later is more effective and economical in practice.

With the different processes involved in the

transformer dehydration and degasification

plant it is evident that the processes should be

neatly designed to tame different oil volumes to be

filtered.

With increasing power demands and scaled up

voltages transformer oil filtration is becoming more

and more demanding and sophisticated. With the

advent of new technology now the water activity or

the water content in the transformer oil is

measurable online and methods of laboratory

testing like the titration method are becoming

limited.

At Transfo Tech. Engineering,

we understand the requirements of the oil

filtration and are committed for resulting a good

transformer performance. Feel free to contact

us, we shall be happy to help you and provide you a quick response.

At Transfo Tech. Engineering, we understand

the requirements of the oil filtration and are

committed for resulting a good transformer

performance. Feel free to contact us, we shall

be happy to help you and provide you a quick response.

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