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Designing a dry-type transformer to function at minus 40⁰C temperatures at an altitude comparable to Everest’s base camp is one of the latest achievements of Johannesburg-based Trafo Power Solutions.
Supplying to a gold mine expansion in Kyrgyzstan, the company has provided a 3,000kVA transformer with a primary 6,3kV and a secondary 400V specification, which will operate at 4,020 metres above sea level.
“The altitude alone presents particular challenges to the design, in terms of cooling,” says David Claassen, managing director of Trafo Power Solutions. “Most large electrical equipment is rated for 1,000 metres or below, so we had to derate this unit to account for the altitude. The higher the location, the less efficient the cooling – and the temperature range on site is between minus 40° C and plus 25⁰C.”
The eight tonne outdoor transformer has a specially designed enclosure to keep out snow, dust and moisture, while also extracting heat. Claassen notes that there is a risk of condensation when the transformer is turned off under these conditions.
“We therefore built into our design a control system for automatically heating the enclosure when the transformer stops operating for any reason,” he says. “The heaters will then, of course, be turned off again once the transformer resumes operation.”
Under the demanding environmental conditions, the enclosure was coated with a corrosion resistant C5 paint plan. The design also included a neutral earthing resistor with special surge protection elements. He highlights that Trafo Power Solution’s strategic partner TMC Transformers – a leading manufacturer based in Italy – has extensive experience in producing transformers for these severe conditions.
“A dry-type transformer is well-suited to these cold conditions as there is no fluid involved in the cooling process, and it is fairly straightforward to provide the necessary heating and cooling as required,” he says. “There is also very little maintenance required, which is a great advantage in a remote location like this.”
With travel restricted by the Covid-19 pandemic, the customer could remotely witness the factory acceptance test conducted at TMC’s IEC-approved facility in Italy, which allows all routine and special testing to be done in-house.
“The online factory acceptance test uses communication technology and cameras around the test bay, including cameras focussed on the technician performing the test,” says Claassen. “This allows the customer to check in detail all aspects of the specifications, and to interact freely with the TMC and Trafo Power Solutions team during the witness test.”
At the start of a project, Trafo Power Solutions will provide customers with a published theoretical test report of the tolerances – in terms of aspects such as losses and impedance – expected by the IEC. These are then compared to the actual readings obtained during the factory acceptance test, where he says the results are invariable well within IEC requirements.