In distribution transformers, low voltage and high voltage windings are winded by means of appropriate winding techniques for related current and voltage conditions, and using round and profile electrolytic copper, high quality insulating paper and transfer board materials. Low and high voltage windings are resistant against atmospheric shockwaves, and the cylinder layer is in winding form.
Mechanical compressions are applied against short-circuit dynamic forces. Sufficient axial and radial channels are ensured for cooling the windings.
The core of transformer is made of cold rolled and grain oriented silicon coil. The core consists of electrical silicon coils of ZDHK, MOH, M1, M2, M3, M4 and M5 quality levels depending on the no-load losses requested by customer.
These sheets are slit via zero burring and they are cut as requested by modern cut-to-length machines. It is possible to form the cores in every form such as step-lap, over lap, 90° cut, perforated and imperforated
TANK and COVER
Transformer tanks and covers are made of medium steel. On tank surfaces of Distribution Transformers, wave wall panels also function as cooler. The lower part of the tank is integrated by means of connecting the walls and frames. Besides, it is possible to use several slices and radiator groups as cooling surface. In the transformers up to 4000 KVA, wave wall panel can be used as cooler. Each tank, the welding works on which is completed, undergoes pressure test before painting. In case of any welding error, it is perceived and the contact error is corrected.
Each tank and cover, whose craftsmanship is over, is subject to grinding. The standard grinding procedure in use complies with DIN norm. If the customer has a special request or detail on grinding, it will be ensured. Upon request, it is possible to coat the tanks via hot-dip galvanized method. Depending on customer request, it is possible to implement a protection box made of plates compliant with ICE 144 STD, and the coating by mountable covers or cables on lateral surfaces of transformer pursuant to BS2562.
PAINTING, DRYING and OIL-PAINTING
Once the r product on s over, the tanks are pa nted w th spray. Standard pa nt ng cons sts of one undercoat, and two layers of topcoat. Total f lm th ckness s not below 105μ. Standard transformer colour s RAL7033, wh ch s called as cement gray. Upon customer request, t s poss ble to pa nt them n d fferent structures (l ke z nc- plat ng), th cknesses and colour codes.
The act ve parts of transformer (Core + Co l) are dr ed n dry ng k lns that operate under h gh vacuum. Dry ng process s carr ed out w th n the frame of a programme wh ch s formed depend ng on voltage and power. O l f ll ng s carr ed out under vacuum.
1. Oil Level Indicator : In transformers wİth an expansİon tank open to atmosphere, the magnet cally functioning oil level indicators are used in order to track and check oil level in expansion tank. Magnetic oil level indicators can have single or double electrical contact. Contact oil level indicators inform the unexpected sudden changes in oil level in form of warning and opening signals. If required, prismatic oil level gauges can also be applied.
2. Dehumidifier : It is used in transforms with an expansion tank open to atmosphere, and mounted on expansion tank. By means of silica gel within, it absorbs the moisture and dust in the air, and enhances the operating safety of transformer. Silica gel amount varies depending on the oil amount within transformer.
3.Oil Temperature Indicator : It is possible to track and check transformer oil upper temperature by means of thermometers placed in thermometer pockets on the cover or lateral surfaces of tank. Thermometers of none, single or double electrical contact with maximum indicator can be applied. Contact thermometers issue warning and opening signals in case the heat in transformer exceeds the stipulated values.
4.Buchholz : Gas Collecting and Warning Relay This relay collects the gases formed by low and high density discharges and arcs to occur within transformer. Relays can be of single or double contact. Warning and opening signals can be obtained depending on the amount of gas collected in relay. Thus, it ensures that the defect within transformer is noticed prior to any major damage. Besides, in case the oil level decreases, due to any reason, so as not to fill completely the relay, the latter informs such situation via warning signal.
5.Hermetic Protective Relay : It is used in hermetic transformers totally closed to atmosphere. It is applied in transformers with a power equal or above 630 KVA. It is a single relay that includes oil level indicator, temperature indicator , Buchholz relay, as well as extra pressure relay.
6.Winding Temperature Thermometer : It is used in power transformers. It gives the temperature to occur on windings according to current temperature relation depending on the current passing on windings. It issues alarm or opening signal depending on the prescribed temperature value.