Tag Archives: high voltage

The Transformer Insulating Oil Filtration Process

The dielectric properties of transformer oil (e.g., breakdown voltage or dielectric loss factor) can be significantly improved by degassing and the removal of water and moisture from the oil.  Only clean and uncontaminated oil with the correct specifications is suitable as the liquid insulation for electric power transformers.

Often though, even new and unused transformer oil can be considered unclean and unsafe for use in electric power transformers as the oil can become contaminated during transport from the oil producer to the transformer operator.  During the time the oil is being used in the transformer, it will absorb moisture, dirt particles, fibers, soot and other products of oil and transformer aging.

The transformer oil therefore, needs to undergo a comprehensive filtering process.  The filtering process must be able to remove contaminants that includes solids, free and dissolved water and dissolved gases.

The filtering process of transformer oil is a complex procedure of removing the above described contaminants down to acceptable levels.  In recent studies, experts have revealed that serious problems can occur when insulting oil makes contact with moisture, flammable gases, and other transformer decay products.  In order to make the necessary correction, the operator should regularly monitor the condition of the insulating oils.

Companies that produce equipment for processing transformer insulating oils, cover a wide range of services and products.  They include such things as machinery for filtering transformer oil, insulation oil cleaners, cleaning systems for lubricants, machines to filter hydraulic oil, regeneration equipment for turbine oils and other industrial oil filtering equipment.  In recent decades, there has become a comprehensive network of high-tech enterprises that operate around the world.  They provide integrated systems and parts for the implementation of the transformer oil filtering and regeneration processes.

The transformer oil filtering process is a continuous circulation of oil through purification units in a closed loop system.  The oil passes through several filters of both coarse and fine filter mediums before the system further cleans the oil through a  vacuum drying, degassing and adsorption process.  The process is designed to remove dirt, sludge, foreign particles, dissolved gas and other contaminants found in the oil.  Moreover, the filtering unit can continuously analyze and control the oil at all stages of the purification process.

All systems for filtering transformer oils should have certain safety features built in such as liquid level detectors and pressure sensors.  These safety features should be incorporated into the design of the cleaning equipment.  They are needed in order to maintain the necessary level of oil inside the transformer and to prevent oil spills

The design of filters and pumps should provide for a filtering process, vacuum and degassing process that is powerful enough to quickly and efficiently process oil, without affecting the continued operation of electric power equipment.  Assessment of the effectiveness of the process is provided with tools for monitoring flow rate.

GlobeCore does all of this and more!  GlobeCore has a line of oil processing equipment that has become the most popular and cost effective equipment in the industry.  Take a look at GlobeCore and see if your company can benefit from the GlobeCore Process!

Transfromer Oil Purification Equipment by GlobeCore


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.


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.