A solar power generating facility recently developed by a South African gold mine has made use of Zest WEG’s locally manufactured transformers to serve this specialised application. Factors like harmonics or ‘noise’ in the current flow mean that solar photovoltaic (PV) applications require specialised transformers, explains Rynard Potgieter, Sales Manager for transformers at Zest WEG. At this site, where 40 MW of renewable energy is being generated, the company 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.”
It has the advantage of not being flammable, so it would not contribute to an explosion or fire. Ester oil also retains heat better, moderating the temperature of the transformer windings while not activated.
The MV and LV terminal boxes of the 5 MVA PV transformers.
The transformer radiator configuration designed for optimal efficiency and style.