From 690 volts to 380 kilovolts
How the electricity travels
When you insert a plug in a socket, you probably just about know that 220 volts will come out. But how do those volts get there? From the North Sea, the renewable energy generated on Gemini travels a long way. It becomes increasingly stronger, to ultimately decrease in strength so that it can be used to power the appliances in our homes. A report.
The 600MW from Gemini is not connected to the network in
one go. That happens gradually and in a
The energy generated by the turbines travels through three conductors; the conductors are surrounded by a plastic layer that earths the 220,000 volts.
The electricity that is generated in the Gemini wind farm has a long way to travel and undergoes different processes along the way. Technical Project Manager Bernard van Hemert explains: ‘The turbine generates electricity at 690 volts. The transformer in the turbine converts it to 33 kilovolts on the spot. Then there are seven to eight windmills in a loop with each other: the combined electricity goes to the OHVS, where the transformer converts it to 220 kilovolts. Then the electricity travels along the 85-kilometre cable that comes ashore in Eemshaven. There, we have a land station full of transformers, where the electricity is converted to 380 kilovolts so that it can be transported over longer distances. And a few kilometres further on, we have reserved a connection point with Tennet, the network operator. After which it enters our homes – in reverse order– as 220 volts.’ In the long run, van Hemert expects the introduction of 380 kilovolt cables that can be laid under the seabed. ‘That technology is still quite new so it first has to become proven technology.’
Spools and condensers are used to minimise electricity loss during transport. ‘We also have smart techniques that we use to get the 600 MW that’s ultimately generated in the wind farm onto the network. That has to be built up gradually.’ For delivery reliability, it helps that Gemini wind farm has configured a number of facilities in duplicate: ‘Two OHVS’s, each with two 180 MW transformers and two export cables. That way, we get the best results. We also carefully monitor the temperature in the cables, for example. And if necessary, we can switch and regulate it.’
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The Gemini lifeline
210 km of cables link Gemini with the mainland. In itself, a wonder of technology. Read more about the cable with a diameter of 30 cm that delivers the generated energy to the Dutch national grid.