Tag Archives: dielectric

Buying and Storing Transformer Oil

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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.

Complete purification of I-12 industrial oil

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I-12 industrial oil is a general purpose oil with no additives. It is made from sweet crude by selective purification.

This oil is used for lubrication of bushings of straight bar and linking machines, spindles of metal cutters, bearings of low power electric motors, and as an operating liquid in positive displacement of hydraulic drives operated indoors.

Combined purification methods of I-12 industrial oil are based on simultaneous influence of several electrical fields or a field with filtration.

The principle of combining electric field influence and centrifical force is implemented in cyclone separators and centrifuges equipped with a special electrical device.

By design, a triboelectric centrifuge purifier is a multifoil rosette with two chargers that create opposite charges in the industrial oil.  The passes through the swirler in a translational-rotational movement.  It them passes the oil through a circular ring space. Due to friction with barriers, contaminants become oppositely charged. Centrifugal force moves particles with a positive charge to the outlet wall where they are coagulated with negatively charged particles.  The charges are neutralized in the coagulated particles.

Then by the force of gravity and inertia, the particles are deposited in a special settling tank.

Comparing hydrocycling efficiency with that of a similar machine equipped with chargers, the chargers are 40% more efficient on average.

When using centrifuges with electrifying devices, the electric field may be obtained by voltage from an external source or by a triboelectric effect.  The triboelectric effect occurs due to rotor friction against special bars.  The rotor is made from a special dielectric material. (Plexiglas, PTFE, or some other dielectric material )

It is also possible to combine centrifugal force with a magnetic field.  It is done by installing permanent magnets into centrifuge systems to capture ferromagnetic particles. Diamagnetic and paramagnetic contaminants are only influenced by the centrifugal force.

The most widespread of combined industrial oil purification systems are devices combining elecrtric fields and filtration effects.  These include magnetic filters, filtering centrifuges and vibration (acoustic) filters.

In centrifuge filtration, the centrifuges operate at relatively low rotation speeds. Contaminants may be removed from the rotor either continuously or occasionally.

A magnetic filter is free from such a disadvange of magnetic purifier as selective removal of only ferromagnetic particles.  Such devices, beside permanent magnets, use special filters capturing non-magnetic contaminants.  An additional filter element (usually a metal mesh) protects the surfaces of the magnets from tar, sediment and other products of hydrocarbon oxidation.

In vibration filters the oil passes through a vibrating porous membrane.  The vibrations prevent sedimentation of contaminants on the surface and reduce hydraulic losses, increasing the filter’s service life.

It should be noted that the combined methods of purifying oil products are not widely used at this time due to the complexity of purifier design.

Transfromer Oil Purification Equipment by GlobeCore

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Application

CMM systems designed and manufactured by GlobeCore can perform the following functions: Degassing, dehydration and filtration of transformer oil, cable oil, turbine oil, and other industrial oils.  The CMM units remove gases, free and soluble water, and particulate matter from oils and fluids.  The CMM units are used in the installation, repair and operation of oil-filled high voltage equipment up to 1150 kV (power transformers, high-voltage switches etc.) as well as industrial turbines.

The GlobeCore CMM units perform the following services:

  • Purifying and drying of Transformer Oil
  • Vacuum filling of Transformers and Electrical apparatuses
  • Drying and Purifying of oil in transformers (on and off-line)
  • Vacuum Drying of Transformers
  • Degassing of Transformer Insulating Oil
  • Filtration of Transformer Insulating Oil

Technical Description

GlobeCore CMM units are designed as multipurpose Transformer Oil Conditioning units for field or factory use.  The units incorporate high capacity multi-stage electric oil heaters,  large capacity Vacuum Pumps with external connections for Vacuum filling work, three (3) stage particulate filtration systems, and connections for a large variety of service applications.

The Unit’s measuring devices include vacuum, pressure, and temperature meters.  The equipment can also be optionally supplied with a “water-in-oil” measuring device.  Installation of a water-in-oil measuring device allows in-line monitoring of water content.

Flow rates are variable from 0 to >10,000 liters per hour (L/H) and heating from 24KW to 210 KW in four stages.  GlobeCore systems are designed for easy operation and maintenance.

The principal functions of transformer insulating oils are to serve as a dielectric medium and as a transformer coolant or heat transfer medium.  In order to perform these functions, transformer oil must have the necessary qualities at the time of initial impregnation and filling at the factory and later be able to maintain the same quality in normal operation.

High Vacuum Treatment improves insulating fluids that includes transformer oils and silicone fluids. GlobeCore transformer oil purification equipment was developed as a result of 30 years of experience in vacuum treatment of transformer oils.

Benefit

Every company dealing with oil-insulated high voltage equipment (transformers, high-voltage switches, turbines, etc.), shares the problem of having to change and dispose of contaminated oil and fluids.  The costs of changing and disposing of insulating oils are frequently very high and need a significant investment in time, labor, and money.  At GlobeCore, our equipment offers a practical, proven and economical method to purify oil so that it can be used again and again for your high voltage equipment.

Thermally accelerated Vacuum Dehydration and Degassing of Transformer Oil has gained wide acceptance as one of the most economical methods for the removal of dissolved water and gases.

On-Site Transformer Oil Purification is the most cost effective transformer maintenance service in existence today.  The GlobeCore CMM units not only purify the oil within the transformer, but actively regenerate the Transformer Insulating System by removing impurities that had become built up within the transformer over time.

Thermo-vacuum purification and degassing of transformer insulating oil, as performed by the GlobeCore Process, will result in the improvement of the condition of the entire insulating medium of your electric power transformers.

Here are some additional benefits of the GlobeCore Process:

  • Removal of dissolved moisture from transformer insulating oil
  • Reduction of combustible gases and oxygen
  • Improvement of insulating oil dielectric values
  • Improvement of transformer insulating oil power factor
  • Extension of oil service life
  • Extension of transformer service life and reliability

We at GlobeCore are committed to provide our customers with high quality products that satisfy technical and economic objectives.  We offer our vast experience in manufacturing, servicing and operation of transformer oil purification systems to your company.

Machines by GlobeCore come with a block of approved original equipment spare parts.  These spare parts meet all specifications required of the engineering process.  Over the years, optimal and high quality components have been carefully selected for our equipment.  GlobeCore guarantees the performance of our machines and the results of the oil treatment processes.  We have placed our equipment in more than 70 countries around the world and a reference list available upon request.

Short Process Description

Hot Filtration Mode

A gear type pump draws in the oil for processing via a valve and a strainer.  Processed oil is then pumped through the cartridge filter, the three-way valve and is then discharged to the processed oil vessel via a connecting line.

The above mode is also used for transformer core drying.  Transformer oil is circulated through the oil purification equipment.  After filtering the oil to remove the particles, the oil is heated up to max. temperature of 800C/1472F.  All residual gases are removed and the moisture is evaporated in the vacuum degassing chamber.  Residual moisture content can be reduced down to less than 3 parts per million (ppm).  Oil purification is a necessary maintenance process for oil-filled transformers and can be employed for removal of moisture from the transformer’s core and solid insulation. Heating of the transformer oil moves the moisture from paper to the oil and allows for its removal from the transformer.  The most common mistake made by operators of transformer oil purification equipment is to stop the drying process after reaching oil moisture content of less than 5 ppm.  After some time, when normal transformer operation conditions exist, the moisture content of the oil increases. It is essential to dry the transformer oil continuously throughout a long period.

Transformer Evacuation

Another required process is the immediate evacuation of the transformer after pumping the insulating oil out of the transformer tank.  The “Vacuum Effect” on the insulation surfaces greatly improves moisture content removal.  The process must be repeated several times before the desired effects will be achieved.

Hot Filtration and Thermo-Vacuum Drying

A gear type pump draws the oil in for processing via a strainer and cartridge filter.  It then directs the oil to the heat exchanger where the oil is heated by the heat conductor.  The oil is then fed to the vacuum drier’s sprayer after being heated to 60C/140F.  The Vacuum Pump maintains vacuum in the vacuum chamber.  a Vacuum can be regulated by valve(s) and monitored on the vacuum meter.  Filtered hot air comes into the chamber and removes gases and vapor from the oil’s surface effectively drying the oil.  The air is then discharged into the atmosphere via an oil separator by the vacuum pump.  A gear type pump then directs the oil into the processed oil vessel.  A programmable thermal regulator switch monitors the plant’s function continuously and maintains the pre-set temperature.

Which kind of Transformer Oil Should my Company Buy?

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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.