Oil-Immersed Large Power Transformer

ELTAŞ strengths are unique engineering and design features and flexibility to meet all the customer requirements.
Every transformer is designed according to its required specification and its application.

The following activities are used to ensure reliability of product:
Design optimization, considering of design relation to labor and material costs, loss evaluation and noise level, distribution of voltage stresses under impulse lightning and switching surge conditions, behavior during short circuit conditions, both transient electrodynamics and continuous thermal withstand analysis of those areas where high electrical stresses can occur, and optimization of the insulation structure design, calculation of stray losses and thermal effects.

Products :

  • Power transformer (up to 250MVA, 420KV)
  • Generator step up transformer
  • Auto transformer
  • Multi winding auto and separate winding transformer
  • Shunt reactor (up to 50MVAR)

Special transformers:

  • Furnace transformer
  • Earthing and auxiliary transformer
  • Package and mobile substation
  • Convertor transformer


Our transformer are designed according to “ core type” design. Slitting and cutting of core is done “ in house”. Core are manufactured from high quality standards also high quality cold – rolled grain oriented silicon steel laminations, which are coated with carlite.


All winding are of the circular type, since this type has the highest resistance against short circuits. Depending on the specific design criteria, layer, helical, disc, partly interleaved or fully interleaved winding are also used.


Tank design is competely done by 3-D CAD on computer, which determines the optimum size and the number and location of needed supports, which makes handling, assembely and instalation easier for customer.

  • All welds are tested, ensuring 100% leak proof seams and maximum mechanical strength.

Cooling system

  • All transformer are equiped with detachable panel radiators, which are connected to top and bottom headers.
  • Most commonly natural air/ forced air cooling is used to accelerate the cooling process (NAN/NAF).
  • Other cooling methods such as forced oil/ forced air (OFAF), Directed oil / forced air (ODAF), forced oil / forced water (OFWF), directed oil / forced water (ODWF) are also available if required.

Engineering Tools

System used for design and drawing of transformer tank, coolers and active part. Reduced lead time and increased accuracy.

May also be used for mechanical analysis. Here, the vibration levels on the end panel of a transformer tank were calculated and compared with the measured values.


  • Software is intended for calculation of two-dimensional plane or axissymmetric electrostatic field.
  • The program of calculation of impulse stresses on main and longitudinal insulations of Transformers. The program is intended for definition of impulse voltages between any points of windings.
  • Program is intended for calculation of transformer tanks, yoke beams and pressing rings for mechanical strength at Short circuit, Pressing, Lifting, Vacuuming and Transportation modes.
  • Program is intended for calculation of electrodynamic stability of transformer windings at short circuit.

Benefits of engineering tools :

  • Reliable design
  • Electrical stresses within safe limits
  • Optimized insulation structure
  • Low risk of failure
  • Long lifetime
  • Optimized tank design
  • Lower tank weight
  • Lower noise
  • Increased reliability

The following accessories are mainly used to protect transformers:

1. Oil Level Indicator

Magnetic oil level gauges are used in order to follow and to control the oil level in the conservator of transformers. Oil level indicators give alarm and tripping signals in case of sudden changes of the oil level.

2. Air Dehumidifier

Air dehumidifier are utilized for transformers with oil conservator. It is connected to the oil conservator. Via silicagel, it removes moisture and dust coming into the conservator. The amount of  Silicagel depends on the amount of oil inside the transformer.

3. Oil Thermometer

Oil thermometers, which are located in thermometer pockets and welded on the top of  the cover or on the side of the tank, follow and control the maximum temperature of the oil. It is available with maximum pointer, without electrical contact or with single or double electrical contact. If the temperature exceeds the estimated values, thermometers with contact give alarm or tripping signals.

4. Buchholz ( Gas Collecting and Alarm) Relay

The Buchholz-Relay collects the gasses which are formed by discharges or arcs with low or high intensity inside of the transformer. It used for transformers with conservator. The relay can be with single or double contact. If certain amount of gas is collected on the Buchholz-Relay, both the alarm and tripping signals are activated. Moreover, Buchholz-Relay sends out an alarm signal in low level of oil. The Buchholz-Relay detects failures like overheating and prevents an increase of failure by signalling.

5. Pressure Relief Device

Even though hermetic protection relay is used in transformers, pressure relief device is used additionally. It helps to cover the pressure that expands inside of the transformer.

6.Hermetic Protection Relay

Hermetically sealed transformers equal and greater than 630 kVA are equipped with a Hermetic Protection Relay. It consists the functions of Oil Level Indicator, Temperature Indicator, Buchholz-Relay as well as Pressure Relay.


Besides, upon customer’s request, special accessories such as winding thermometer, digital thermometer, gas collecting unit can be used  for  oil immersed power transformers.