Maintenance service to transformes

Nowadays, transformers are present in multiple sectors, being fundamental parts even in critical processes. Nowadays, there are a series of techniques, tests and trials that allow the operational continuity of these units, as well as associated maintenance and good practices.

Although each installation has different characteristics, the following are the usual ones or the ones that must be complied with in the standard.

  • Disconnect the equipment from the mains taking the necessary measures.
  •     Check the safety system for overtemperature.
  •     Check the safety system for overvoltage in the transformer.
  •     Checking the current and earth leakage systems.
  •     Checking other indicators
  •     Checking the oil level as well as possible leaks.
  •     Dielectric rigidity test of the oil
  •     Checking, cleaning and adjusting all electrical connections, fixings, supports, guides and wheels, etc.
  •     Checking and cleaning insulators
  •     Checking the operation of the fans if necessary
  •     Cleaning and painting of the chassis, casings, tank and other external elements of the transformer susceptible to rust or residue.



  • Measurement tests of the ohmic resistance of the windings.
  • Transformation ratio.
  • Polarity, angular displacement and phase sequence.
  • Vacuum losses and excitation current at nominal voltage.
  • Impedance voltage and losses due to load at nominal voltage.
  • Dielectric tests:
  • Applied voltage
  • Induced voltage
  • Insulation resistance
  • Tests Physical-chemical analysis
  • Chromatography of gases dissolved in oil
  • Content analysis
  • Filtering and degassing process
  • Transformation ratio tests
  • Insulation resistance tests
  • Power factor tests
  • Resistance tests
  • Revision changers
  • Accessory inspection and testing
  • Oil change

Avoiding equipment failures, unexpected plant shutdowns, and generating significant cost savings associated with its unplanned repair or renovation, are some of the advantages that represent the implementation of a transformer maintenance program.

  • Overheating
  • Secondary Overvoltages
  • Insulation failure
  • Heating of insulators
  • Overpressure valve operation
  • Downloads in bushings
  • Pressure loss
  • Low oil level

= Continuous overload

= Bad external connections

= Bad ventilation – hot surrounding air

“High input voltage

= Faults in the tap changer

= Continuous overload

= Damage due to manipulation during installation

= Atmospheric discharges

= Defect in the connections

= Connectors not connected

= Insulation failure

= Short-circuit

= Heavily contaminated atmospheres and/or insulators with high contamination (dust or salinity)

= Verify gaskets, welds, or blows on valves and radiators

= Check for oil leaks

= Verify gaskets

The need for preventive maintenance in electrical installations, both High, Medium and Low Voltage, increases depending on the damage that could be caused by a breakdown. In the case of expensive equipment, its revision must be carried out at the intervals established in your installation project, adapting at all times to the special characteristics of its use, location, etc.


  • Thermographic study.
  • Gas chromatography.


  • Screw tightening.
  • Dielectric rigidity test to oil.
  • Insulation resistance test (Megger).
  • TTR test.


  • change of nozzle gaskets
  • exchange of nozzles
  • Dielectric oil replacement
  • change of valves and manometers
  • Change of tap's

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