Transformer Oil Filtration Machine (working principle)

 



Transformer oil is the lifeblood of power transformers, it serves as both an insulating medium and a cooling agent. Over time, this vital fluid can degrade due to contaminants like moisture, dissolved gases, solid particles, and even acidic compounds. These contamination compromises the oil's dielectric strength and cooling efficiency, posing a significant risk to the transformer's performance and longevity. 

The transformer oil needs to be absolutely clean and dry and this is where a transformer oil purifier or filtration machine comes in. There are 3 main technologies used in oil purification systems, and they are named below.
1) Centrifuge Filtration
2) Vaccum Dehydration 
3) Coalescers.

While all of these three technologies listed above are effective in their own way Vacuum dehydration Oil Purification method is preferred with transformer oil because is it removes all water from the oil (Free Water, Emulsified Water and Dissolved water) along with entrained gases restoring the oil its new state.

We will explain the working principle of a transformer filtration machine using MACROTECH FILTERALL MTHV 3000.


Fig 1.1 Image showing Flow path of the Transformer oil form inlet to outlet.

Components Of Vaccum Dehydration Oil Purification Machine.

(1) Inlet Strainer
(2) Inlet Pump
(3) 50-micron bag filter
(4) Heaters
(5)10-micron Filter
(6) 0.45 to 1-micron filter.
(7) Degassing & Dehydration Chamber
(8) Outlet Pump
(9) Moisture Reciever 
(10) Moisture Seperator
(11) Vaccum Pump.

How it works.

At Atmospheric pressure water boils at 100°C however if we lower the pressure by creating a vacuum we can boil water at lower pressures. For example, at a vacuum pressure of -2.888 psi (or -22 inches of mercury), water boils at just 60°C. This is crucial to the process because by boiling water out of the oil  at a lower temperature, we can prevent degradation of the transformer oil.


Fig 1.2 Flowchart

When we turn the system on the vacuum pump starts and creates a vacuum up to -2.888 psi in the degassing chamber then it cuts off.

The inlet pump picks up to draw oil from the transformer or storage tank , the inlet strainer on the line serves as the suction strainer for the inlet pump. it removes large solid contaminants like dust, metal particles, and sludge that could damage the inlet pump.

Some models have a 50µ filter this is the first stage of filtration that removes larger solid contaminants that could otherwise clog the hearer and finer filters upstream. a 50 bicron particle could be as big as a grain of sand or hair.

After this the oil goes into the heater 21.6kw heater to raise the temperature of the oul to around 60–80°C. The aim is to lower the viscosity of the oil allowing for better filtration and also to make the release dissolved gases and moisture much easier in the degassing/dehydration chamber.

The oil now flows into a series of Filters , 50µ and 0.45 -1µ depending on the exact model of the filtration machine. this filters remove medium size particles and very fine particles from the oil stream. A 10 micron particle could be as tiny as a single particle of talcum powder or milk and a 1 micron particle is microscopic compares to a single smoke particle.

After filtration the oil is introduced into the Degassing chamber from the top. The oil i spread thin over a structure in the degassing chamber that increases the surface area of the oil. Because the oil is at 60–80°C and the chamber is at a very low-pressure water in the oil begins to boil immediately it enters the vacuum chamber. Trapped gases like CO, CO2 , Ethane and H2 in the oil is also released from the oil.

Clean oil now leaves the degassing chamber from the bottom. A foam trap is installed on the line to ensure foam doesn't go into the outlet pump.

The steam and the gases released from the degassing chamber also leaves from the top of the degassing chamber through the evacuation line there is a moisture receiver on the line that serves as Condensate Pot to collect the condensed moisture (liquid water) that has been separated from the system.

The moisture receiver has a drain valve and it must be drained from time to time. The Moisture seperator uses a coalescing filter to capture tiny water droplet an make them caolece into bigger droplets and dtop to the bottom of the separator. The moisture separator is important because it protects the vacuum pump as Liquid water can damage a vacuum pump.

Fig 1.3 Moisture Seperator

The transformer oil purifier works sequentially, combining filtration, heating, and vacuum degassing to restore the quality of transformer oil.

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