The 45MVA transformer will receive 33kV from the wind turbines and step this up to 132 kV for the main power grid. Stuart Brown, sales team leader, transformer division at Zest WEG, says the design and construction of the power transformers shows the high level of expertise and technical capacity in South Africa.
“With two of the few local transformer manufacturing operations in the country, we have the added advantage of being able to draw on the technical experience of our parent company, the world-wide WEG group,” says Brown. “In designing power transformers for renewable applications, we gain valuable insights and important skills transfer from WEG experts in the US and Brazil.”
Brown highlights, for instance, that the high harmonics content is a feature of the inconsistent cycles associated with renewable energy sources. This requires a specialised design and manufacturing capacity to ensure that a transformer in this application delivers its intended lifespan and high reliability.
He says the local manufacture of main power transformers can contribute significantly to the local content of renewable power projects, which by their nature must import much of their specialised equipment. This helps project developers to comply with the Department of Trade and Industry’s local content requirements.
“Zest WEG’s B-BBEE Level 1 status allows renewable energy developers and contractors to align their projects with South Africa’s transformation goals,” he adds.
The transformer was built at Zest WEG’s Heidelberg facility which, combined with the WEG global operations, offers the market more than 30 years of experience in the design and production of larger power transformers. Following comprehensive testing at the facility’s laboratory in 2019, the transformer was delivered to site and assembled under the supervision of Zest WEG engineers in January 2020. They also conducted full on-site testing of the unit, as well as cold commissioning.
“The size of the transformer – at 5,7 metres high and 7 metres long – meant that it could not be transported in one piece,” Brown says. The total weight of the assembled unit is 70 tonnes.
Ongoing technological improvements and constant upgrades at the Heidelberg plant ensures its state-of-the-art capability. The testing conducted at the factory includes lightning impulse withstand tests and temperature-rise tests, especially relevant to simulate the potentially high temperatures where transformers are located.