Specialised dry-type transformers for Saldanha port upgrade

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Dry-type transformers

TRANSNET’s upgrade of its port facility at Saldanha Bay will include dry-type transformers from specialist company Trafo Power Solutions.

The company is supplying specialised transformers for the Tippler 3 project at the iron ore load-out station. Factory-acceptance testing was completed in December 2019, according to Trafo Power Solutions managing director David Claassen.

The construction of a third tippler at the Saldanha Bay port is to sustain iron ore export volumes of 60 million tons per year when the existing tipplers are refurbished in future. It will integrate with the rail system bringing ore via the 860 km line from mines in the Northern Cape. Key aspects of the new infrastructure comprise the 285 ton tippler itself, a loading vault below ground and a conveyor tunnel. New buildings, service roads, bridges, railway lines, conveyors, lighting and bulk electrical supply infrastructure are also part of Transnet’s upgrade project.

Trafo Power Solutions’ contract was for the design, supply and commissioning of five dry-type transformers. There are two 1 000 kVA units and a 3 150 kVA unit, both stepping down from 11 kV to 400 V. The other two units 3 500 kVA and 4 500 kVA capacity respectively, taking 11 kV to 3,3 kV.

To resist the corrosive sea air, all the transformer enclosures will be manufactured from 3CR12 grade of stainless steel. The enclosures are also to be IP33-rated to ensure a high level of ingress protection against moisture and dust.

“The enclosure design also incorporates cable boxes and Type C, totally enclosed plug-in bushings for the terminations,” he says. “This provides a boot covering which is touch-potential safe, and also provides for efficient plug-and-play installation.”

This is a significant improvement on the regular lug and bolt copper connection, which would just be shrouded by a heat-shrunk material. The special terminations also facilitate easier maintenance or removal.

“The units will provide the medium-voltage supply for the Tippler 3 project and its associated infrastructure, including equipment like conveyors,” he says. “All the transformers will be supplying non-linear load to a certain extent, so they have been designed with a K-factor of four.”

The K-factor is a measure of a transformer’s ability to withstand the heating effects of non-sinusoidal harmonic currents created by electronic equipment. The higher the K-factor, the greater the harmonic heating effects.

As dry-type transformers are cooled without the use of oil, these units will receive forced ventilation when a preset temperature is reached. This ventilation is provided from a row of fans which Trafo Power Solutions has designed to be bolted below the location of the transformers.

Designed locally by Trafo Power Solutions, these dry-type transformers are manufactured in Italy by strategic partners TMC Transformers, experts in cast resin transformer technology. All products are routinely factory-tested according to IEC standards, but type-testing and special testing can also be conducted.

“The standard applicable to dry-type power transformers is IEC 60076-11,” Claassen says. “TMC’s advanced laboratory facilities allow us to conduct the full range of tests in-house, in accordance with what these standards and whatever other requirements are designated by the customer.”

At Saldanha, Trafo Power Solutions is also responsible for building auxiliary protection and control panels, which it locates remotely from the transformers. These include temperature control sensors that communicate with the port’s broader control and monitoring network.