Transformer Rewinding, Repairing & Overhauling

Transformer rewinding, repairing and overhauling

As the largest facility in the region our facility is capable of performing overhauling, rewinding, field services and life assessment studies on transformers ranging as well as offering a wide range of transformer re-engineering and field services.

Our range for the rewinding, repairing and overhauling are:

  • 231V up to 230kV, ratings from 150kVA up to 200MVA (rewind and repairing)
  • 231V up to 380kV, up to 227MVA (overhauling service)
  • Additionally, we also:

  • Supply of various types of windings to the customers as per their requirements.
  • Reverse engineering and redesigning through up-to-date design techniques.
  • Repair and overhauling of Off Circuit Tap Changers and On Load Tap Changers.

  • Disposal of the failed unit is no longer your only option. Enduring lead times of one year or more for new units and solving the problem of different dimensions and termination locations is no longer necessary. alfanar technical services can provide the right solution for power/distribution/special transformers.

    alfanar technical services has the distinction of being the first facility in the region to repair, rewind and commission a 200MVA transformer locally.

    Factory Services


    Repair & Retrofit

    Power transformers are vital to ensure a trouble-free supply of power with no interruptions. Whether your transformer has failed or you are planning timely corrective maintenance our team of experts is available for short-term and long-term repairs.

    alfanar Technical Services performs the repair, overhaul, and modernization of your power transformers that are performed in our dedicated repair shop. Our repair facilities handle to overcome all problems which arise during operational life cycles of the transformer including:

    • Rewinding to meet original specification with thermally upgraded Insulation
    • Installation of advanced technology on-load & Off load tap changers
    • Replacing old and absolute bushings and new hybrid bushings
    • Replacement of old rusted and leaked tanks, Radiators.
    • Drying out and overhauling of transformers
    • Replacement damaged core
    • Installation of Technologically upgraded measuring and monitoring devices on transformer
    • Rewiring protection accessories with new added features

    Our engineers work closely with local electrical contractors or in-house maintenance staff to design a program that meets your needs. We can rebuild your original transformer on site and in place if the situation demands.

    Vapor Phase Drying Plant


    At alfanar Technical Services (ATS), our Mission is to sustain our prominence as the provider of high-quality, precision-engineered repair and rewind services for Transformers upto 200MVA, 230kV. And to reinstate our commitment, we have commissioned the largest Vapor Phase Drying plant in the region, assuring higher and efficient quality and a much lesser delivery period.


    VPD is used in drying of cellulosic insulation of the transformer winding which requires that the moisture content be brought to 5 ppm levels before impregnation of the winding with transformer oil, recovery of the oil and discarding the moisture. The fluid basically acts as a heat carrier to the insulation.


    Advantages of Vapour Phase Drying Plant

  • Reduction in Process Time
  • Prevents Oxidation During Drying
  • Uniformity of Temperature (Heating)
  • Excellent Quality of Dryness
  • Associated Components Drying
  • Test Facility

    Testing laboratory of ATS is well equipped to carry out following tests on transformers as per various standards like IEC , IEEE etc.

    The Transformer test lab of alfanar technical services has been designed to perform all routine tests on transformers upto 200 MVA, 230kV class. The Laboratory is equipped with the most modern testing instruments.

    Routine Tests

  • Measurement of voltage ratio and check of phase displacement
  • Measurement of no load losses and Magnetizing Current
  • Measurement of short-circuit impedance and load loss
  • Separate Source AC withstand voltage test
  • Induced AC voltage test
  • Partial discharges Measurement
  • Insulation Resistance Measurement
  • Lightning Impulse Test
  • Switching Impulse Test
  • Tests of on-load tap-charges
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    Special and Type Tests

  • Temperature Rise Test (Short-circuit method)
  • Measurement of Sound level
  • Lightning Impulse chopped on the tail test
  • Capacitance and power factor measurement
  • Measurement of zero-sequence impedance
  • Measurement of harmonics in no-load current
  • Measurement of vibrations
  • Frequency Response Analysis (FRA test)
  • Die Electric Frequency Repose Analysis ( DFRA)
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    Oil Tests

    Site Services


    On Site Servcies

    The site services provided by alfanar technical services, is an alternative to reduce the downtime and cost in the maintenance of the transformers. We mobilize a complete team of fully equipped experts to the sites to carry out the diagnostics, overhauling and repair of the transformers, without compromising on the Quality of service

  • Assembly Testing & Commissioning of new and Old transformers
  • Attending Shutdowns and preventive maintenance activities
  • On site OLTC inspection and preventive maintenance
  • Oil Filtration / Regeneration / Passivation activities
  • Internal inspection of core and windings with repair
  • Drying CCA at Site
  • On Site Winding Replacement
  • Shifting of transformers & other sub station equipment
  • Attending all types of leakages
  • Refurbishment / Repair / Replacement Cooler Installations
  • Transformer Drying-Out, Oil Filtration and Passivation


    We dry out moist transform at Site by various methods

  • Oil filtration & heating.
  • Vacuuming, Oil filiation and heating
  • Vacuuming, Oil filiation, heating and Nitrogen Carry out Oil filtration as PM and oil replacement activities
  • We have full range of Filter machine from 250 Lits to 10,000 LPM.
  • We have more 100 ,000 ltrs of Mobile Storage Tanks
  • We have separate vaccum system
  • We carry-out supply of Passivator and passivation services of the oil

  • Oil regeneration


    alfanar Technical Services' experts provide you with a proper preventative maintenance program, to achieve an indefinite life to the cellulose. Our mobile unit allows expediting this process at your facility on live transformers, thus allowing close to zero downtime and high savings.

    Regeneration of insulating oil is the process of removal of contaminants and products of degradation such as polar, acidic or colloidal material, as determined by oil and transformer tests.

    With on-site regeneration and desludging, the oil is processed on site in the transformer tank. It is circulated from the bottom of the main tank, heated, and directed through 'structured clay columns', then filtered to particulate removal of 0.2 micron, vacuum treated and dehydrated before it is returned to the top of the unit via the conservator tank. The process is continued until the oil exceeds the specified minimum required levels. The method employs adsorption and thermo vacuum (dehydration and degassing) treatment in restoring the oil.

    Benefits achieved through Transformer Oil Regeneration

  • Life extension of a limited resource
  • Control of strategic asset is retained
  • Economically advantageous
  • Expert Services

  • Harmonic Measurement study
  • As Third party Inspections for FAT & SAT and witness for Insurance cases
  • Transformer feet screening & Report preparation
  • Transformer Interchangeability Study
  • Based on customer requirements we offer in house & on Site training programs in:
    • Transformer Manufacturing and testing
    • Preventive maintenance on the job for transformer and OLTC
    • Oil sampling and testing
    • On Site testing and calibration


  • Supply of complete Replacement Transformer as Turnkey Project
  • OLTC and Bushings and transformer Components
  • Study supply Replacement /up gradation new cooling system
  • Supply installation of transformer and DGA monitoring systems
  • Supply of new oil
  • Supply, Modification and installation of Transformer bus-duct and cable boxes
  • Supply, Installation and handover of Transformer on-line oil drying unit