22.12.2023 - Aluminium Association

Transformers are a crucial component of the power supply systems for urban and transport infrastructure, and industrial facilities. The reliability and safety of this electrical equipment are, in part, due to the quality of the windings, which are made from aluminium strips. Before the SA-55 project was initiated at SAYANAL, transformer manufacturers had to import a significant amount of aluminium strips. Now, the upgraded factory will supply high-quality strips to consumers in Russia and the ex-USSR countries.

Great Transformations
There are either oil-filled or dry transformers. In an oil-filled transformer, the magnetic core and windings are cooled by transformer oil, which also serves as electric insulation between the live and grounded components. In a dry transformer, the windings and magnetic core are cooled by circulating air, either naturally or forced.

Aluminium is the optimal material for power transformer windings. Using aluminium instead of copper has significantly reduced the weight of these units.

Oil transformers have been in use in a wide range of sectors for many decades. They can operate reliably under overloads and across a broad temperature range: from -60 to +40 C. However, oil-filled transformers are a fire hazard (category B1), and therefore they can only be installed outdoors. Furthermore, they require regular maintenance, which includes the analysis of the moisture and gas content in the oil (except for the TMG line of sealed transformers).

The TMG transformers are sealed and completely immersed in oil. Temperature variations in the oil volume are compensated by the elastic deformation of the corrugated tank walls. The low voltage windings of these transformers are made from a special strip, combining ease of winding with high reliability. The application of advanced technologies, winding and insulation materials has resulted in a design that minimises the negative impact of external short circuit currents. This has also reduced the material consumption and, consequently, the cost of the product.

The reliability and safety of dry transformers with cast aluminium alloy windings allow their use in the construction of residential and public buildings, hospitals, airports, subways, ships, coal mines, oil platforms, and nuclear power plants.

Dry transformers are installed in administrative buildings, cultural and entertainment centres, and educational buildings, both indoors and outdoors. Airports, offshore platforms and ports, storage terminals, utility facilities, and industrial sites would be unimaginable without this equipment. Transformers are an essential component of wind turbines, solar power stations, and combined heat and power plants.

Unlike oil-filled transformers, dry power transformers with cast windings are maintenance-free and fire-safe (category D) as they are made from flame-retardant materials. With some protection, they are resistant to network disruptions. The use of epoxy resin as insulation ensures the safe operation of the transformer in a range of conditions: from residential or office spaces to mines, oil platforms, subways, and nuclear power plants.

The large cross-section of the aluminium conductor provides a large cooling surface, which is critical for the cast winding, as the only way to dissipate heat is through direct contact of the conductor with the heat-conducting material of the cast winding.

The Aluminium Association’s experts see great potential in expanding the use of aluminium conductors in transformer windings, both dry and oil-filled.

The Bright Strip
For transformer manufacturers, aluminium has become almost the only choice due to its high conductivity, corrosion resistance, and superior heat transfer compared to copper, not to mention its cost-effectiveness (aluminium is significantly cheaper than copper). Furthermore, using aluminium instead of copper in transformer windings significantly reduces the weight.

It is worth noting that 1050, 1060, 1070 and 1350 aluminium alloys are used in transformers.

Currently, all new lines of general-purpose transformers with a capacity of up to 16,000 kVA are designed with aluminium windings.

Thanks to their design features and no risk of oil leaks, dry transformers are used in areas where environmental safety is a priority.

Windings for dry and oil transformers are manufactured by special winding machines from aluminium transformer strips. The strip thickness ranges from 0.2 to 3.5 mm, and the width varies from 10 mm to 1,600 mm.

The most common process involves filling the windings with an insulating compound under a vacuum. During winding, materials such as paper, cardboard, polyester film or fibreglass are used as interlayer insulation. This results in a compact, solid structure with high load resistance.

Full-Scale Production in Sayanogorsk
Until recently, before 2022, the main issue for transformer manufacturers was the lack of local production capable of supplying the entire product range. Before the launch of the CA55 project at SAYANAL, the value chain was as follows: RUSAL, KUMZ, SMZ and AMR supplied slabs and strips to the MOST-1 site in Mytishchi. There, at the Metal Machining Centre, strips were machined to the required dimensions and mechanical properties. However, the supply was insufficient, forcing MOST-1 to purchase some strips from EU countries.

The faults in that value chain were obvious. For this reason, a CA55 upgrade project has been launched at the SAYANAL foil rolling mill in Sayanogorsk. This project will soon reduce the strip production time thanks to more efficient logistics and, more importantly, the concentration of all production in a single plant.

Until 2022, the transformer strip was imported and then cut in Russia. RUSAL purchased equipment for full-cycle production at a single location, the SAYANAL plant.

As a result, SAYANAL has gained a unique status as the first domestic full-cycle facility with a complete range of domestic and imported equipment. The factory can now roll strips to the required thickness, and perform straightening, washing and cutting. All of this is available at a single site! We should highlight the extensive digitalisation of the CA55 project: for product quality, all the manufacturing variables are controlled by special software and integrated control systems.

Naturally, the quality of the transformer strip largely depends on the consumables used. To compensate for the shortage of spare parts for imported equipment used in the CA55 project, the Sayanogorsk plant arranged for the supply of consumables from domestic manufacturers. In a short time, they managed to replace the imported components that had become unavailable because their manufacturers had left the Russian market.

In the finishing straight
The equipment installed at SAYANAL can produce not only transformer strips but also spacer frames for double-glazed windows and strips for building wall panels called siding. The wide range of products makes SAYANAL’s offerings popular among customers and ensures full utilisation of the equipment.

The capabilities of the equipment are virtually limitless; it can meet the demands of even the most discerning customers. Currently, the transformer strip is supplied to the largest companies in Russia and the ex-USSR countries. Pilot batches of the strip have been delivered to all dry transformer manufacturers.

Using the SA-55 project equipment, SAYANAL can produce up to 55,000 tonnes of products annually.

The SAYANAL plant, using the CA55 equipment, can produce up to 55,000 tonnes of products per year. In five to seven years, this figure is expected to double due when a new brownfield project is completed. This volume of high-quality transformer strips is sufficient for all of Russia and the ex-USSR countries.