Power Transformers


Prestige and reliability

Tadeo Czerweny S.A. produces high-power and medium-power transformers within a range from 5 to 300 MVA and with voltages of up to 230 kV. These transformers are manufactured with tap-changers without voltage and / or automatic on-load tap-changers, according to service requirements and conforming to IEC, ANSI, IRAM, ABNT or specific customers’ Standards.
Tadeo Czerweny S.A. offers as well specific solutions for special requirements satisfying every requisite related to each type of operation, for example, low noise level, low losses, clamp cover in low and medium voltage, flanges in high voltage for ducts coupling in SF6, special designs and transportation and installation service.

General building

All of them are designed making the voltage distribution, faced with requirements of atmospheric type impulses, similar to a linear distribution. In every case it is checked that the highest demands produced in the windings by these impulses, considering the real parameters, are resisted within the appropriate safety coefficient. Likewise, the windings and their anchor system are designed intending to make the short-circuit electrodinamic stresses minimum and get them evenly distributed.
All the windings are manufactured with conductors made of electrolytic pure copper. Depending on the power and voltage, the conductors used in the building of power windings can be rectangular metal sections (flat bars) or continuously transposed conductors (C.T.C.)
Every winding, before the definite assembly, is carefully dried and pre-stabilized with values of pressure higher than the maximum ones given in external short circuits. During this process all the dimensions are checked, adjusting each one if necessary, according to the results obtained from real parameters by the Engineering Department. This way, all the windings are dimensionally leveled or balanced and / or the support structures are designed to minimize the electrodinamic short circuit stresses.
The whole process of winding manufacturing entails a strict quality control, which checks all the dimensions, cleaning conditions and the non-obstruction of the cooling ducts, backed up by auto- control and inspections of the Quality Department.

The cores are made of grain-oriented silicon iron sheets with a thickness from 0,23 to 0,35 mm in standard commercial qualities (M3, M4 or M5 type) or HiBi type (grain-oriented silicon iron sheets treated with laser), the latter on requirement using loss capitalization formulae. All the sheets used have electric isolation on both sides through a thin film of inorganic material (also known commercially as “carlite”) which has high mechanical resistance to mineral oils and high temperatures.
The quality of each consignment is guaranteed by the origin certificates of the materials (tests carried out by the Manufacture Plant) and by the rigorous tests carried out at the reception and during the entire process of production by our Quality Department. In the core production process, the iron silicon sheet is first cut into strips which afterwards are cut in lengths and shapes designed by our Engineering Department. This process is performed by automatic and high production machines controlled by computer, which guarantees cuts with minimum margin for error and allows the design of cores STEP LAP type. This means significant reduction in the values of eddy losses and mainly a reduction of around 50% in the inrush current with respect to the traditional cores with joints at 45º.
The core assembly is finally performed horizontally on devices specially designed to facilitate the perfect assembly between columns and yokes and to allow, once the process is finished, to place the core totally assembled in a vertical position, safely and fast. During the entire process, strict dimensional controls are carried out.

The insulation system of our transformers is designed so that the dielectric stresses get evenly distributed. In order to reach this, and depending on the voltages, we have designed columns with power rings which balance the electric field in the terminals of High Voltage windings. The insulation between windings of different voltages is designed so that solid insulation (transformer-board barriers between windings) resists the maximum dielectric stresses which appear during trials. Afterwards, the necessary oil channels are inserted in this solid insulation to permit heat outlet. In every case, it is checked that the electric fields in channels, barriers and terminals are within the working limits of the corresponding insulators. In the final assembly, all the active part is dried with temperature and high vacuum, ensuring the dielectric properties of all the insulation system designed for each transformer in particular.
Finally, the bathing process with highly refined oils is also carried out using temperature and high vacuum. In all cases the final dielectric properties of the oil are strictly controlled (including humidity levels) before allowing the access to the transformer tank.
In this way, with insulation drying treatments and bathing processes using temperature and high vacuum, all the insulation system properties, planned during the design stage, reach maximum performance.

All the tanks are entirely built in the foundry of the modern industrial plant of Tadeo Cerweny S.A., which along the last years has focused its development on light structures. These structures, are adequately reinforced to guarantee minimum vibrations and low noise, and also to resist absolute vacuum and strict overpressure tests requested by the Manufacturing Standards and / or by our customers, allowing oil treatment and drying in location. Before being painted, the sealing of all the foundry products are checked with the most modern detection methods based on penetrating ink systems and afterwards, cleaned by a shot blasting process which guarantees maximum adherence to the scheme of surface protection designed for environment conditions indicated by our clients.

The transformers are a very important link in the transmission and distribution of electric energy. Therefore, reliability and quality have to be guaranteed from the very beginning and during their life span. That is why Tadeo Czerweny S.A. set up its Quality Assurance System following ISO 9001 Standards, system certified in January 1997 by the international auditor DET NORSKE VERITAS.
In compliance with this system’s specifications, the process quality guarantee starts when our Sales Department initiates a potential commercial relationship with customers advising them professionally about their real needs.
It goes on in the Engineering Department with the most updated computing resources and calculation and verification programmes. The following stage is manufacturing. Here the control begins with the arrival of raw material to the plant and goes on through the whole process of building of parts, assembly and up to the final product. However, delivery is not the end, since our top priority is the satisfaction of customers. The efficient guarantee service and maintenance offered by Tadeo Czerweny S.A. is then the perfect end that consolidates this satisfaction.