Oil immersed transformers


Oil immersed transformer

Energy saving, easily adapt to the grid, easy connection process
  • oil type transformers
  • oil immersed power transformer
  • liquid filled transformers
  1. oil type transformers
  2. oil immersed power transformer
  3. liquid filled transformers

Low noise solution

Efficient transformers with reduced losses

High frequency-low losses

Environmental friendly

Easily adopt to the grid, easy connection process


Customized design

Our product advantages

  • winding


    The windings are made of oxygen-free copper , so the load loss of is lower and the electric performance is better.

  • Iron core

    Iron core

    The three-limb iron core is made of oblique cut Grain-oriented, seven-step silicon steel laminations insulated on both sides, guaranteeing low losses and low noise. These values are even improved by laser treatment. It is protected on the surface with a flash-proof varnish in order to prevent the sheet from corrosion and to reduce the noise. 

  • The Tank

    The Tank

    The transformer is fully sealed, which ensures the stability of oil quality, extends the service life,  maintenance. At the same time, the tank composed of corrugated radiator adopts phosphating and multi-layer anti-rust spraying technology to produce, which has good weather resistance.

Related product parameters

Main Specifications
Transformer Typeoil imemrsed type 
Rated powerup to 20mva
Rated voltageup to 36kv
Frequency50/60 HZ
Phasesingle or three phase
Oil preservationHermetically Sealed/ Conservator/ Free Breathing
Tap changeroff-load or on-load
Winding materialAluminum/ Copper
Dielectric liquidsMineral oil / Dimethyl Silicone/ Vegetable Oil
Vector groupsDyn11, Yyn11 (according to customers requirements)
Coolerscorrugated wall or radiator
Accessories :


Oil level gauge

Transformer tank

pressure relief valve

Tap changer

Oil Thermometer



Factory Test

For each transformer are prepared and issued a test report, in accordance with IEC 60076.  except for routine tests, we also offer type tests and specialised tests to meet all customer requirements. We make what matters work for our customers in a safe and reliable way. 

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Routine test

 a) Measurement of winding resistance

 b) Measurement of voltage ratio and check of phase displacement

 c) Measurement of short-circuit impedance and loss

 d) Measurement of no-load loss and current

 e) Dielectric routine tests

 f) Tests on on-load tap-changers, where appropriate

 g) Leak testing with pressure for liquid-immersed transformers(tightness test)

 h) Tightness tests and pressure tests for tanks for gas-filled transformers

 i) Check of the ratio and polarity of built-in current transformers

 j) Check of core and frame insulation for liquid immersed transformers with core or frame insulation

 Type test

 a) Temperature-rise type test

 b) Dielectric type tests

 c) Determination of sound level for each method of cooling for which a guaranteed sound level is specified

 d) Measurement of the power taken by the fan and liquid pump motors

 e) Measurement of no-load loss and current at 90% and 110% of rated voltage

 Special Test

 a) Dielectric special tests

 b) Winding hot-spot temperature-rise measurement

 c) Determination of capacitances windings-to-earth, and between windings

 d) Measurement of dissipation factor(tanδ) of the insulation system capacitances

 e) Determination of transient voltage transfer characteristics

 f) Measurement of zero-sequence impedance(s) on three-phase transformers

 g) Short-circuit withstand test

 h) Measurement of d.c. insulation resistance each winding to earth and between windings

 i) Vacuum deflection test on liquid immersed transformers

 j) Pressure deflection test on liquid immersed transformers

 k) Vacuum tightness test on site on liquid immersed transformers


Varelen offers a complete range of power and distribution transformers designed to grant the reliability, durability, and efficiency required in utility, industrial, electrical distribution substations, power generation, voltage regulation, mining, traction and commercial applications. Transformers can be used for indoor or outdoor applications and can be provided with off-load and on-load tap changers.
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wooden case packing
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inner packing.jpg
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Contact us

Varelen Electric Co., Ltd

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