The switchgear is similar to the fuse box in your home, only on a much larger scale. The switches allow the electricity generated by the turbine to flow into the power grid. Alternatively, they stop the flow of energy in the event of a problem such as a lightning strike at the turbine or too much electricity on the grid.
The size and power of the Haliade-X require switchgear that can handle 66,000 volts of energy. The high voltage level is crucial to ensure that when the energy travels via cable from the turbine to the shore, there is minimal power loss. But existing gear with that capacity, which is normally used for small, land-based power plants, was way too large to fit inside the tower of the turbine. And while onshore wind turbines can use gear located in substations separate from the turbine towers but connected by cables, the harsh conditions at sea, especially in the deep waters where the Haliade-X will live, require that the gear be housed safely inside the tower. “The real challenge was to make it very compact because you don’t have a lot of space inside a wind turbine,” says Dirk Uhde, executive product manager for gas-insulated substations at GE’s Grid Solutions business.
It was a challenge the GE engineers were willing to accept. Over the last three years, through a combination of modification and innovation, they built a compact switchgear that can handle Haliade-X’s energy demands. They adapted small “T” connectors usually used in lower-voltage equipment to connect the gear to the network. They also built new, smaller surge arresters, which dampen the voltage in case of a surge from something like a lightning strike. The result: the F35, which, at 2.4 meters high and 3.7 meters long, is 30 percent smaller than previous 66 kV switchgears.
The years of hard work were necessary. The alternative would have been using lower-voltage equipment, such as 33 kV switchgear, that might fit inside the tower but would mitigate many of the benefits coming from a larger wind turbine. “We want more and more power coming from these offshore turbines,” Uhde says. “If we want to make it efficient to bring this power back to land, it has to move at a higher voltage.”
GE’s Grid Solutions business is debuting the new switchgear at this week’s CIGRE show in Paris. The gear will be included in all Haliade-X turbines, which should begin shipping in 2021. It will also be available for use in other power plants, including industrial and urban substations. The smaller footprint means that the F35 can easily fit under a city building or inside a warehouse at an industrial power plant. The F35 is also designed to use g3, a greener insulating gas than the SF6 normally used to protect the gear.
“In the coming years, the offshore wind market is going to require bigger and bigger wind turbines,” Uhde says. “Equipment like this will help make those turbines as efficient as possible.”