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Buying and Storing Transformer Oil

Purificación de aceite de transformadores, , , , , , , , , , ,

Purchasing transformer oil is an important financial decision for your company.  It should be done very responsibly.

First, the buyer must a choose a brand of oil.  This requires careful consideration based on the type of equipment being used and the operating conditions the oil and the oil’s abilty to meet those conditions.

Second, the cost of the oil must be considered.  A small price difference in the cost of just one liter small can turn into a significant amount of money when purchasing a large volume of oil.

There are no universal recommendations for buying transformer oil. There are however, online services allowing buyers to compare transformer oil prices from various suppliers.  It is up to the buyer to research and choose a reliable wholesale distributor or retailer.

If you have already purchased transformer oil that meets the correct specifications and quality standards, then it is time to think about oil storage.

The practical way to store the oil is to use clean and dry, steel air tight vessels.  The tanks are usually coated with an oil resistant material inside.  The outside of the tanks should have anticorrosion and light reflecting coating.  The acceptable range of temperatures for storage of transformer oil is -40ºС to +60ºС/-40ºF to +140ºF.

The vessels should be equipped with valves for filling and draining as well as a manhole for cleaning, inspection and repairs.  Breathing systems must be equipped with silica gel or zeolite cartridges that can be monitored by special monitoring devices.

Three days after putting the oil into a storage tank, samples are normally taken for laboratory analysis.  Transformer oil in storage should be tested at least once a year for the following parameters:

  •  flashpoint;
  • dielectric strength at 90ºC/194ºF;
  • water extract reaction;
  • acid neutralization number;
  • particulate matter content in mircons; and
  • free water and moisture content.

It is also recommended to test the dissipation factor at 90ºС/194ºF at least once a year.

Each time the oil is tested for quality and purity, the results must comply with the parameters of fresh transformer oil regardless of the length of storage. Otherwise, the oil must be purified and regenerated to restore the oil to its new and clean condition.

GlobeCore offers a line of oil purification units under the CMM classification. These units improve color, remove acids, bases, and other aging products from any turbine, dielectric insulating oil, and industrial oils.

One of the advantages of the GlobeCore CMM line of units is their ability to regenerate oil on an energized transformer.  Another important advantage is the ability to reactive the fuller’s earth sorbent inside the unit many times over, reducing downtime for sorbent replacement and replenishment.

After the processing of transformer oil with GlobeCore equipment, transformer insulating oil is restored to an as good as new condition.

Purchasing a GlobeCore CMM unit gives you a modern efficient machine that is easy to operate and service.  The use of GlobeCore equipment and GlobeCore Process will extend the service life of the oil and the transformer significantly.

Which kind of Transformer Oil Should my Company Buy?

Tierra Fuller, , , , , ,

A great number of manufacturers and distributors of transformer oils operate in international and national markets.

Transformer insulating oil is a dielectric liquid that is intended for cooling and insulating electric power transformers and other high voltage equipment.  Transformers remain an indispensible part of the electric power generation and transmission industry.

In scientific terms, transformer oil is a product of crude oil refining.  The performance properties of transformer oil depend heavily on the quality and parameters of the raw material.  The performance of the oil is defined by the positive and negative properties of the crude oil.  Chemical composition of oil is quite complex.  It includes the following components: paraffin (10-15%), naphtenes or cycloparaffins (60-70%), aromatic hydrocarbons (15-20%), asphalt (1-2%), sulfuric compounds (<1%), nitric compounds (<0.8%), naphtenic acids (<0.02%) and antioxidation additive (0.5 – 0.5%).

Transformer oils must be highly resistant to oxidation and must not form sludge or emulsify when coming in contact with water.  Anti-oxidation additives are an important component and can be found in virtually all types of transformer oil.  When selecting an oil for your equipment, be sure to look for oils that have good antioxidant additives included since they will inhibit the oxidation process considerably better than uninhibited oils.

The efficiency of such additives is based on the ability of the additives to react with active peroxide radicals that form as the result of hydrocarbon oxidation reaction and are the primary carriers.  The presence of additives in transformer insulating oils slows the aging of the oil.  As soon as the additive is depleted, the oil ages in about the same amount of time as an oil without the the antioxidant additives.  Without the additives, the oil aging process will accelerate.

Two of the main characteristics of transformer oil are its viscosity and density.  These have a pronounced affect on the function of the oil.  Higher viscosity may mean better dielectric strength, but may reduce the ability of the oil to transfer heat and cool the transformer.  Optimal kinetic viscosity of the oil at 20 ̊C is about 28-30×10-6 m2/second.

The oil’s “Dissipation Factor” is responsible for the oil’s dielectric properties and protects the transformer’s electrical system from possible short circuits.

These and the other characteristics of transformer oil are improved by the use of high quality crude oil, deep refining and introduction of additives that increase the oil’s oxidation stability and reduce corrosion.

When oil is significantly oxidized due to the influence of water, solids, air and other gases, and high temperatures, the oil should be replaced.  If the degradation of the oil’s properties is not detected in time, transformers can and will fail.  When oil decays, it can no longer serve as a dielectric insulator and starts to react with the metal of the transformer tank and hinders cooling and may lead to short circuits.

The following are some of the different kinds of oils that may be purchased in the local market:

VG type oil is made from paraffinic crude oil by a catalytic process with the addition of an antioxidant  additive.  It is a good dielectric and is rather stable against oxidation.  It is mostly used in higher voltage equipment.

GK type oil is made of sulfuric paraffinic oils by hydrocracking.  It also contains ionol, an antioxidant, that ensures good stability and dielectric properties of the oil.  It is another kind of oil used in higher voltage systems.

TKp oil is made from low-sulfur naphtenic crude by an acid-alkali purification process.  The oil also contains antioxidant additives.  This oil is recommended for equipment with voltage up to 500 kV.

Oil selection depends not only on the type of electric equipment you are using, but also on the individual requirements of the facility.  Most of transformer oils are universal.  In all cases, the correct selection of oil type with consideration of local climatic and physical operating conditions ensures reliable and stable operation of electric power equipment such as high voltage transformers and switch gear.