Any robustly functioning transformer oil is susceptible to deterioration and such decay begins immediately after the oil is being dispatched from manufacturer, thanks to high temperatures and exposure to oxygen and moisture. Such entities encourage catalytic action within the transformer leading to oxidation and cracking of transformer oil and finally insist the necessity for transformer oil filtration system.

By products of deterioration

The by-products of such oxidation increase acidity and sludge formation and accelerate deterioration in transformer oil with huge loss in the insulating properties. Transformer oil as an asset is maintained by periodical treatment of the insulating fluid and by maintaining is dielectric attributes. The motives of transformer oil filtration system also include maintaining parameters such as efficient cooling, protecting transformer coil from chemical attack and preventing sludge formation.

Tests for transformer oil

Specific tests that assess dielectric strength, moisture content, neutralization value, interfacial tension, dielectric dissipation factor, resistivity, flash point, pour point, viscosity, sludge test, dissolved gas analysis (DGA) and test for oxidation stability precede transformer oil filtration process.

Types of transformer oil filtration

Sludge can be removed by employing filter candles or by centrifugal system. transformer oil filtration system using candles can performed either with edge filter or with depth filter. Though these edge filters can be reused for around four times, cleaning them is laborious. Though edge filters hold large capacity of sludge, cleaning it with reverse pressurised dry air or nitrogen and drying the paper stack in oven or bright sun light demands expertise.

Filter cartridges can be chosen from sizes 500 microns to 0.5 micron size do not have moisture storage and can be easily replaced.

Centrifugal filtration

Centrifugal system is employed to remove dirt or sludge from the oil which can also be slow type ones. These slow type centrifuges do not require additional electric motor to spine the cone. This transformer oil filtration system has limited capacity because it cannot eliminate dirt less than 10 microns size.

Power filled centrifuges can remove water that are in free form but not those which are either less than 5 ppm or dissolved. Besides they save the expense required to change filter elements.

Vacuum filtration

Vacuum filtration is used to remove dissolved moisture, dirt, air and other gases and operates in two stages which encompass low temperature and high vacuum. The transformer oil enters through an inlet pump where solid and magnetic particles up to 1 mm size are held back. Following this oil is heated and particles up to 2 microns are filtered. The oil enters a vacuum chamber where moisture and other gases are separated from the oil. The oil is spread and allowed to drop owing to principles of gravity. A thin film on the surface is exposed to vacuum and dissolved gases and moisture are eliminated so that the insulating attributes of the oil are restored.

Mechanical filtration

Mechanical impurities in transformer oil include suspended particles like sand, iron particles, fiber fragments and carbides formed due to oxidation which occur during transportation and storage of transformer oil when the container is not properly cleaned or if container is not tight.

In such cases, plate and frame oil filter press, portable oil filter cart, vacuum oil purifier and transformer oil regeneration unit are used to remove these mechanical impurities.

Conclusion

Timely efforts to remove impurities in transformer oil are rewarding in terms of output, operations and profits and transformer oil filtration system cannot be overlooked at any cost.

Media contact

Company Name: Hering VPT
Contact Person: Detlev Bastek
Email: Send Email
Phone: +49 9831 8834666
Address: D-91550 Dinkelsbuhl,Ernst-Schenk-Str.10
Country: Germany
Website: http://www.hering-vpt.com/