The MV and LV terminal boxes of the 5 MVA PV transformers
Locally manufactured specialised transformers were recently supplied to a solar power generating facility developed by a South African gold mine.
Zest WEG sales manager: transformers Rynard Potgieter explains that factors such as harmonics or ‘noise’ in the current flow mean that solar photovoltaic (PV) applications require specialised transformers and that the company’s expertise and local manufacturing capacity enabled it to supply the required transformers.
40 MW of renewable energy is being generated at the mine’s solar power generating facility and Zest WEG supplied 10 of its custom-designed transformers of 5 MVA capacity each. The units for this PV project were manufactured at the company’s Wadeville factory.
“In this application, our transformers will step up from 690 V current to 11 kV,” says Potgieter. “A dual input, single output configuration is a cost-effective innovation, allowing one transformer to be fed by a number of string inverters through the dual input.”
He noted a further innovation of the recent PV project was the use of ester oil – rather than normal oil from hydrocarbons – as a coolant in the transformers. With ester oil being a focus of dedicated research at the WEG Group’s head office in Brazil, Potgieter said this option brought considerable benefits to the South African solar plant.
“From an environmental point of view, ester oil does not carry the risk of contaminating land or water if it happens to leak from the transformer,” he says. “Operationally speaking, it is also able to withstand higher temperatures without degrading.”
Ester oil also has the advantage of not being flammable, which makes it safer to use, and it retains heat better, moderating the temperature of the transformer windings while not activated.