Electricity grids designed so generators switch off when system loses synchronicity, expert explains
Barry Hayes, Associate Professor in Electrical Power Systems at University College Cork, said credence has to be given to the explanation offered by the operator of the Portuguese grid as to why the outage happened, but it is best to avoid speculation until a definitive view is provided.
The operator of the Portuguese power grid, REN, said power supply interruptions in Portugal were due to a fault in the Spanish electricity grid.
Extreme temperature variations in the interior of Spain caused anomalous oscillations in the very high voltage lines, it said, causing a phenomenon known as 'induced atmospheric vibration'.
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The oscillations caused synchronisation failures between the electrical systems, REN said, leading to successive disturbances across the European network.
However, later in the day the Spanish prime minister, Pedro Sanchez, said they did not yet have conclusive information as to the reasons for the power cut.
Electricity grids, Hayes said, have been described as the largest machine ever built by mankind, with millions of components that all need to work together.
The major power generators linked to the grid have to run within a certain tight frequency band and are all synchronised with each other.
'As soon as you go outside that frequency range all of the generators are programmed to disconnect instantly because you can cause a lot of damage to the generators and surrounding grid,' he said.
'That's what happened at 11.30 today: all of the large generators in Portugal and Spain just disconnected.'
As far as he could make out, there had not been any particularly high temperatures in Spain or Portugal on Monday, he noted.
Getting the grids back up and running requires a 'black start' where one generator is started up, and then another, all synchronising with the local grid, and progressing across the country until the whole grid is operating again, he said.
What happened in Spain and Portugal was one of the largest, if not the largest, electricity blackouts ever in Europe, Hayes said.
The blackout will have left a huge amount of data in its wake, along with other evidence, that can be poured over in the coming period for why Iberia lost its power on Monday. The evidence is likely to provide 'huge learnings' that will be of interest to experts around the globe and help the effort to minimise the risk of such outages in the future, the academic said.
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