Britons are hoping the grid will hold steady this winter after a report on the country’s biggest outage in a decade was put on hold.

The government investigation into the cause of an Aug. 9 blackout that affected around a million British customers is on ice pending the outcome of national elections on Dec. 12, with insiders saying it likely won’t get published until next year.

A spokesperson confirmed that U.K. electricity system operator National Grid ESO had not made any changes to its operating procedures following the outage.

“This has happened only three times in 30 years, and Great Britain has, statistically, one of the most reliable energy networks not only in Europe, but anywhere in the world,” said Ben Davis, external affairs manager.

According to a detailed timeline put together by National Grid ESO, a lightning strike on a transmission circuit north of London caused the almost simultaneous shutdown of Hornsea One, which is the world’s largest operating offshore wind farm, and the Little Barford gas station.

This took almost 1.4 gigawatts off the grid. The loss outweighed the gigawatt or so of power that National Grid ESO had in reserve at the time, causing grid frequency to fall and prompting the automatic disconnection of 5 percent of Britain’s electricity supply. 

The supply was restored to all customers within 45 minutes. A week after the incident, Hornsea’s owner Ørsted admitted the wind farm had experienced a technical fault.

The company said: “The relevant part of the system has been reconfigured and we are fully confident [that] should this extremely rare situation arise again, Hornsea One would respond as required.”

"New technologies introduce new risks"

Observers said that while the circumstances surrounding the August blackout were unusual, similar occurrences could not be ruled out as the U.K. increases its reliance on renewable energy.

"It is rare that two key sources of power fail almost simultaneously, but it is not unheard of,” said Tom Vernon, managing director of Statera Energy, an energy storage system operator whose battery assets were pressed into action on August 9.

“With the increasing reliance on wind and solar in particular, new stability and reliability problems can be expected in the future,” he said. “Clear policy support is needed from government to build up the country's backup provision."

Meanwhile, an analysis of the outage by European energy consultant Paul-Frederik Bach concluded that “the result of increasing shares of wind and solar power will be decreasing short-circuit capacities and rotating inertia.”

This will in turn lead to more rapid frequency changes and less stable voltage vectors, the analysis found. “The risk of blackouts will depend on the measures taken by National Grid as the penetration of new production technologies increases,” Bach told GTM.

“New technologies introduce new risks. I think that the August power disruption offers an excellent opportunity to learn and to eliminate some of the new risks.”

In October, the National Grid Electricity System Operator did get the ball rolling on an inertia tender, the importance of which may well have been amplified by the blackout.

Britain is already heading into the winter season with holes in its offshore wind fleet. The 400-megawatt Rampion Offshore Wind Farm, which was commissioned off the Sussex coast last year, was taken offline on Oct. 26 after suffering a high-voltage electrical system fault.

Local news reports this month said it could be “a few weeks” before operations might be restored at Rampion, although National Grid said the loss of the 116-turbine wind farm would not affect local electricity supplies.

Peter Osbaldstone, research director for European power and renewables at Wood Mackenzie, confirmed the risk of a blackout like the one in August remained very small.

"Events earlier this year should not be taken as any sort of signal that winter 2019/2020 is going to be especially difficult,” Osbaldstone said. “Any power system can fail, and they are becoming more of a challenge to keep in balance. But I've not seen anything to suggest the Great Britain system is in peril.”

National Grid has traditionally been conscientious about planning for winter electricity provision and provides a detailed outlook of energy requirements every year, Osbaldstone noted. “Big problems don't go under the radar."


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