Insulating Transformer Oil

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ELECTROL® today synonymous with the most trusted name in transformer oils. Widely used in transformers, oil immersed circuit breakers and switchgears. Transformer oils are mineral electrical insulating oils processed from super refined, carefully selected premium basestocks. Some of the outstanding attributes of ELECTROL® are

  • Excellent dielectric properties resulting in minimum power loss
  • High resistivity leading to better insulation values between windings
  • High flash point and thermal stability facilitating reduction in evaporation losses
  • Long life performance and excellent ageing characteristics, even under severe electrical stress
  • Virtually devoid of corrosive sulphur, leading to enhanced stability and protection against corrosion
  • Wider operating temperature range, resulting from higher flash and lower pour point
  • Available in a wide range of grades to fit every requirement and meeting every possible specification


In the conventional sense, transformer oils provide cooling, electrical insulation, indicative information on health of transformer, have system compatibility and are expected to give long life performance.

However, ELECTROL® Transformer Oils, designed for use in the new millennium, go beyond the above conventional expectations and provide:

  • Longer life under severe electrical stress and at higher temperatures
  • Have higher Flash and lower pour points to facilitate wider operating temperatures.
  • Have No corrosive sulphur and cap on total sulphur and aromatics to provide additional safety against corrosion.
  • Nil PCB Content and cap on polycyclic aromatics for enhanced electrical and oxidation stability.


Range of ELECTROL® Transformer Oils includes Uninhibited, Inhibited, Trace Inhibited and Special grades as outlined in the following Table.

Series Grade Conforming to Standard
Uninhibited   ELECTROL®   IS 335
ELECTROL®-A IEC 296:1982/BS 148:98 Class I
ELECTROL®-U IEC 60296:2012
ELECTROL®-B IEC 296:1982/BS 148:98 Class II
Inhibited         ELECTROL®-X IS 12463
ELECTROL®-IA IEC 296:82/ BS148:98 Class IA
ELECTROL®-IB IEC 296:82/BS148:98 Class
IIA & ASTMD3487 Type II
ELECTROL®-I IEC60296:2012 & ASTM D3487 Type II
ELECTROL®-IH IEC 60296:2012 – High Grade
Trace Inhibited ELECTROL®-T IEC 60296:03 & ASTM D3487 Type I
ELECTROL®-TH IEC 60296:2012 – High Grade
Special Grades ELECTROL®U/N42 IEC 60296:2012 (Naphthenic Grade)
ELECTROL®I/N42 IEC 60296:2012 (Naphthenic Grade)
ELECTROL®HF300 ASTM D 5222 : 2000 (High Fire Point)

In addition to the above, ELECTROL® Transformer Oils are also offered in other grades conforming to JIS, AS, DIN and other international / Regional specifications. Contact us for your specific requirements


In recent years, presence of corrosive sulphur in transformer oil, originating from the base fluid used in the oil has been a matter of serious concern. There have been numerous documented cases of failure traced to presence of corrosive sulphur, leading to elaborate investigations all over the industry. Naphthenic base oils, traditionally regarded as the best base fluids for transformer oils cannot be made totally devoid of sulphur, even by the best available techniques. Some manufacturers use passivators as additives in transformer oils to reduce the effect of corrosive sulphur. This approach only marginally reduces the risk of corrosive sulphur effect. The key to transformer oil performance therefore is directly linked to use of better base oil with zero sulphur made from advanced refining technology.

Modern techniques for production of high quality iso-paraffin base oils involves severe hydrocracking, followed by hydroisomerization to produce outstanding iso-paraffin base oils with zero corrosive sulphur. Any residual wax in the oil is converted to base oil. The refining technique totally removes sulphur, as well as other undesirable constituents like oxygen, nitrogen, metallic compounds, aromatics and inorganic salts. The result is a highly stable water-white iso-paraffin base oil ideally suited for manufacture of premium quality transformer oils.

All paraffinic based ELECTROL® Transformer Oils are formulated from highly stable iso paraffinic base oils of the purest Group 2 and Group 3 Specifications. As a result, these products offer highest security against corrosion in usage