Oil Immersed Distribution & Medium Power Transformers
ELTAŞ A.Ş. manufactures:
- Oil immersed distribution transformers. These transformers are used to decrease the medium voltage (3.3 -36 kV ) to low voltage level (≤ 1000 V)
- Medium power transformers. These transformer ranges are mostly preferred at city transmission lines, industrial facilities and power plants.
Distribution and Medium Power Transformers can be ordered as single phase or three phased. Inhibited or uninhibited mineral oil are used as a cooling medium. If requested, non-flammable fluids can be used as well.
According to the customer request;
- with ONAN, ONAF, ODAF , OFAF, OWAF cooling systems,
- as open to atmosphere with conservator,
- with off-load tap changers or on-load tap changers
- with cable box or protection box,
- with bushings with ceramic insulators or with resin type plug-in bushings.
The purpose of ELTAŞ A.Ş. is to fulfill customer’s requests completely and to provide highest quality. ELTAŞ A.Ş. manufactures distribution and medium power transformers according to customer requirement, contract requirements or technical standards such as TS 267 60076-1, IEC 60076-1, BS 171, DIN, ANSI, ENEL, ENDOSA, CSA. etc.
Transformers used in solar power plants are the main product of ELTAS A.Ş. in the liquid immersed distribution transformers group. These transformers, which have been produced in large numbers, are customized according to the needs in the field. They can be designed for single or double inverter connection.
Designs and production solutions for specific brand inverters are also possible. Among these solutions, there are also transformers for “solar skid” applications, which are being preferred frequently in recent years.
These transformers, almost all of which are designed as hermetically sealed, have a static sc reen as standard. When the transformer is completely filled with oil, an integrated pr otection relay is installed as standard. Optionally, this relay can be equipped with a PT100.
Depending on the constraints such as size and cooling capacity, ELTA S A.Ş. design and production capability is 6 MVA for a single secondary transformer while it is 10 MVA for double secondary transformer. Solar transformers can be made more compact by utilizing high temperature insulation material, thus inc reasing thermal class of transformer.
ELTAS A.Ş. can optimize the rated power of a transformer with respect to a given load curve (solar load profile). In this case, the transformer is operated at overload during peak hours. However, since the transformer is going to rest during night hours, overall ageing rate is lower than 1. It means that transformer ageing is slower than nominal ageing rate, thus inc reasing transformer overall life.
In solar skid applications, the dimensions and terminals of the transformer are customized to be suitable for LV and HV switchgear connections and skid dimensions. Busbar type bushings are commonly used in LV terminals while on HV side, plug-in bushings are mainly used. Bushings can be indoor or outdoor type, depending on requirements. In accordance with the skid design, the terminal outputs can be located on the transformer cover or side wall.
Some optional features are:
- Cable box
- Busduct flange
- Oil bund (10% additional capacity)
- Hydrocarbon filter for oil bund
- Bushing locking mechanism
For the low voltage coils, either copper or aluminum can be used as conductor material. The windings are made of foil or a flattened and paper or nomex insulated wire. If the coils are made of foil, the layers are insulated using a thermal upgraded paper as well as a covering made of DDP resin.
Depending on customer’s requests, copper or aluminum conductors are used in high voltage windings. Coils are wound with fully automated computer-controlled machines. The layer insulation looks like a dagger, because of the stripped electrical insulation paper ( kraft or thermal-upgraded, diamond patterned ). The structure of this specially formed layer insulation increases the ability to withstand the impulse voltage. The layer insulation also helps in achieving another important goal: to produce a rigid coil without space. In other words a coil of excellent quality. The isolation class is generally “A”. According to customer demand production at B, F, H or C isolation class is also available.
Cores of transformers are made of cold rolled grain oriented silicon steel. Cores are produced by using first class quality of steel. The choice of the material is made according to no-load values required by the customer. Cores are cut to length without burr by modern transformer lamination cut to length machines produced by GEORG and TUBOLY. Cores are produced as step-lap, over-lap, 90° cut with or 45° without holes.
The assembly of core, coil and top cover are designed according to increase the resistance against short circuit forces. The top cover, including the active part of standard transformers, is mounted to the tank with bolts. Another application is direct assembly of active part to the tank. The connection of parts of the top cover, high voltage bushings and the arching horns are made of stainless materials or of materials covered by a special coating which is resistant to corrosion. The arrangement of the bushings, the accessories, the protection box or the cable box is done on the cover or the side of the transformer according to customer requests.
Tanks and top covers for transformers are made of mild steel. Cooling surfaces of distribution transformers are constructed with corrugated walls and they also form the lateral surfaces of the tank. Bottom plate, sides and frame are sealed by welding.
For transformers up to 4000 kVA , corrugated walls can be used as cooling surfaces. Also, it is possible to use radiators as cooling surfaces. Every transformer tank needs to pass an oil leakage test after welding. Therefore, each tank is taken under pressure after being produced. Finished tanks and top covers are sandblasted commensurate with DIN specifications. If the customer has specific requests or demands related to sandblasting, ELTAŞ A.Ş. has sufficient machinery to fulfill all these requirements. It is possible to enclose the bushings on the top cover into a protection box made of appropriate steel according to IEC 60144. According to BS 2562, the cable box can be installed to the sides of the tank.
Transformers are in the colour of RAL 7033 as a standard. Transformer tanks are painted by the method of dipping or spraying. Method of painting is chosen in accordance with customer requests and working conditions of the transformer. For example, Class C1 – C2 – C3 – C4 – C5-I – C5-M paints compliant with H2S can be used against corrosion. ELTAŞ A.Ş. can offer transformers with various applications (zinc coating), various film thicknesses or various colours according to customer demand. Also, if requested, hot dip galvanized tanks can be produced.