Why UK blackouts happened – and the probability of them happening again

The major blackout that struck Britain on Friday was not due to the use of wind generation on the power network, scientists have said.

Experts now believe the disconnection of a gas-fired power plant and wind farm triggered the power cut that caused widespread panic leaving more than a million National Grid customers without electricity.

The shortages began on Friday evening and quickly plummeted many into panic.

Travel was severely disrupted when all flights were grounded at Newcastle Airport, whilst in London the shortages forced many commuters at stations, including Kings Cross, to wander around the labyrinthine passages of the underground with nothing but their mobile phone torch for guidance.

Scenes became even more distressing when a backup generator failed at Ipswich Hospital consequently leaving many patients vulnerable without the full medical support they needed.

What was the causes of the blackouts

Experts have sighted the temporary closure of a gas-fire power plant in Barford, Bedfordshire and the Hornsea offshore Wind farm in the North Sea to trigger an automatic shutdown that resulted in electricity supplies in the West Midlands, South Wales, the South East and the North of England to be cut off.

The dip in frequency below the optimum levels of 50 Hz to below 48.88Hz caused the blackouts when the Grid switched off power to over a million of its customers to prevent a full system melt-down.

Claims of a cyber-attack or the failure of wind farms have been denied and a spokesperson for the Grid as labelled the event as an independent occurrence.

Professor Tim Green, Co-director of the Energy Futures Laboratory, Imperial College London, said he believed it was a gas fired plant and wind farm that had disconnected from the grid.

He said: "[The] first generator to disconnect was a gas fired plant at Little Barford at 16:58.

"Two minutes later Hornsea Offshore wind farm seems to have disconnected.

"This would seem to be a technical failure [or] error. [It] might be linked to disturbance caused by first generator failing – might not.

"Will need to wait for National Grid's full technical investigation to get to bottom of that.

"There was a lot of wind power today [Friday] and consequently less gas used. A system with little gas plant running does need careful management because when generators fail the frequency responds more quickly."

He said the power loss event did "not appear to be due to wind generation reducing owing to reduced wind speed".

"If that were the case there'd be reduction across many wind farms in same area," he said.

He explained that the loss of two generators would cause a dip in frequency of the country's AC power system, normally maintained at near 50Hz.

To counter-act this there can be "load shedding" which entails disconnecting some customers from power to keep the rest of the system running.

Professor Jon Gibbins, Professor of CCS at the University of Sheffield, and Director of UK CCS Research Centre, noted that solar power was decreasing as the sun went down at the time of the issues hitting the UK grid.

He said: "Possibly something didn't come on reliably to replace the lost solar power at one of these steps, frequency dropped and there was not enough reliable and responsive power sources already up and running to kick back in time before load had to be shed to stop grid frequency dropping too far.

"And perhaps the low frequency also caused some other generation sources to trip."

But Professor Gibbins said more data was needed to examine in detail what happened.

Are other power shortages likely to happen?

However, recent worries have arisen with the Grid experiencing fluctuation in frequency levels regularly over the last few months.

On May 9th levels fell to a worryingly low of 49.55Hz and on the 11th of July they dropped to 49.58Hz.

Both occurrences have provoked worries about just how random an event Friday's blackout was as it may have been an exposure of the Grid's incapability of maintaining its normal levels and it was only on Friday when the frequency was neglected enough to result in blackout.

Co-Director of the Energy Futures Laboratory, Tim Green, stated that this level of frequency fluctuation was "above average."

Tom Edwards, an analyst at the energy consultancy Cornwall Insight, describing it has a "one in a ten-year kind of event.”


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