Oil reclamation and drying

INGETRAF has experience in the oil reclamation and drying of the active part, ensuring our customers a high quality service and reliability.

Oil treatment transformers


In a transformer, the dielectric oil and paper is the base of the insulation system.

Paper is the primary insulation and oil has as one of its functions to protect and increase the mechanical strength and the dielectric performance.

Inside the transformer are carried out a series of chemical reactions that are influenced by the presence of moisture, oxygen and metals causing oil oxidation (acid formation and sludge) and decreased polymerization degree of the paper, these being the major causes for reducing the expectancy life.

The OIL RECLAMATION, is a process by which using chemicals and adsorbent media to eliminate the acidic, particulate matter and products from the oil deterioration.

By this process an oil of similar conditions to new oil is obtained, thereby extending the life of the insulation and the transformer itself.

The Oil reclamation can be performed in two ways:

  • Transformer energized
  • Transformer de-energized

Each has its own benefits and advantages which must be analyzed for each transformer, and in that way take the decision to choose what is the best method.

Oil Heating / Vacuum

The water may be present in the oil in various ways as described below:

  • Dissolved water
  • Emulsified water: Small drops mixed in the oil.
  • Free water: Precipitated water in the tank bottom.

The effect of moisture on the properties of oil depends on the form in which is located a small amount of emulsified water, for example has a marked influence in reducing the dielectric strength.

The oil heating/vacuum is one of the most efficient process in reducing the water content to very low values forms. The oil heating/vacuum in the oil is subjected to heating and vacuum for a short time interval.

In addition to removing moisture from the oil, the process executes a degassing and removal of the more volatile acidic compounds.

The oil heating/vacuum procedure can be performed with transformer energized or de-energized and like in the oil reclamation; each case must be studied separately to make the right decision for the most appropriate procedure.

Oil machine
Oil machine

Drying of the active part

Transformers water is distributed through the whole insulation system (paper-oil) in an irregular way, because the paper has a higher affinity for water, most moisture is impregnated to it; direct consequence of this is the rapid deterioration of the paper and therefore decreasing the life of the transformer.

The results of the analysis of moisture content in the oil show only a small amount of water that actually exists in the transformer, for this reason it is recommended that in the oil moisture analysis study takes place in the paper, in order to determine which will be the procedure to be followed.

In cases where the humidity of paper has passed the recommended values, oil heating/vacuum treatment of the insulating oil is ineffective since this does not eliminate the moisture in paper and after a while this moisture migrates into the oil again, as a result of this, oil heating/vacuum procedure would have to be repeated. For these cases it is necessary to perform a drying process of the active part of the transformer (Inner part of the transformer mainly consists of the coils and core), which guarantees the elimination of paper moisture and oil, thereby obtaining insulation in good condition to continue operating reliably.

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