Big new thyristor valves meet big new test centre
Meeting huge needs
Brazil’s Rio Madeira hydro project will be using new thyristor valves designed by Alstom Grid and tested in a gigantic new test facility in China that is one of the few places in the world capable of carrying out such complicated work.
[4] China and Brazil have a lot in common. Both economies are growing fast, both countries cover huge areas, and both have considerable hydroelectric potential. Unfortunately, in both cases the hydro dams are thousands of kilometres away from the economic powerhouses. That is why the world’s longest HVDC transmission line is in China, bringing power from the Xiangjiaba dam to Shanghai, 2,071 km away. But China won’t hold the record for much longer, since next year the 2,375 km Rio Madeira line will carry electricity from the Amazon region to São Paulo, the world’s tenth largest city in GDP terms. As a world leader in hydro equipment and services, Alstom is a key player in both the above projects, designing and implementing solutions for the challenges such vast networks pose.
Six-inch thyristors have recently become commercially available.
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And as Russell Preedy, leader of Alstom Grid’s Valve Design group in Stafford, UK, points out, it is not just the distances that are growing: the transmitted power of HVDC schemes is increasing rapidly too, with both current and voltage now at levels never seen before in the market. “This has a considerable effect on the design of the main items of high voltage equipment in the HVDC station,” he says, “not least the high voltage thyristor valves that form the heart of the converter. Until recently few HVDC converters had operated at current ratings above 3,500 Adc because the largest-diameter silicon on which thyristors could be based was 125 mm (5 inches). However, 150 mm (6 inch) thyristors have recently become commercially available and are changing the rules with respect to current ratings."
