A huge electricity blackout that left more than one million Brits in the dark earlier this month was caused by a lightning strike, according to preliminary findings presented by the country’s grid owner on Tuesday (20 August).
On 9 August, more than one million British consumers were left in the dark for nearly an hour as a large-scale power cut caused chaos on the rail network and disrupted flights in and out of the UK. Hospitals were also affected.
Initial reports suggested that the combined failure of a gas-fired power plant and wind farm, located more than 100 km from one another, had caused the outage by tripping the electricity grid’s fail-safe measures.
Critics of renewable power were quick to claim that the wind farm’s failure was the true cause of the blackout, although Business Secretary Andrea Leadsom later said that “the incident was not linked to the variability of wind power, a clean, renewable energy source that the government is investing in”.
National Grid launched an investigation into what it dubbed “a highly unusual event without precedent in the past ten years” and released preliminary findings on Tuesday.
In its report, the grid owner said that a lightning strike, which hit the grid at 4:52 pm local time, was “associated” with a chain of events that saw fail-safe measures disconnect 5% of the UK’s electricity supply in order to protect the other 95%.
Electricity generators are not supposed to fail due to lightning strikes so National Grid has dubbed the incident “extremely rare and unexpected”.
In draft conclusions, the investigators found that the amount of electricity generation that failed, more than 1.3 megawatts, exceeded the 1 MW of backup supply kept in reserve to deal with emergency events and keep the grid functioning.
Small-scale power providers like some renewable sites and diesel generators are not visible to National Grid and could have accounted for further losses during the outage, it conceded.
Despite the blackout disruption, the report insists that protocols were properly followed and that power was restored in accordance with established procedures. Government regulator Ofgem will now launch its own inquiry.
If the regulator finds that procedures were not followed correctly or even lacking, then the firm could be hit with a financial penalty.
“We welcome the commissioning [of a] review into the incident – to identify lessons and recommendations for the prevention and management of future power disruption events,” National Grid added in its report.
The company will now work with the operators of the gas-fired power plant and wind farm to understand “the exact failure mechanisms” that led to the power cut.
Grid management has been under scrutiny since the blackout and Grid sources recently told British media that the operator has a policy of limiting the use of four cross-Channel interconnectors that it co-owns.
With a combined capacity of 4 gigawatts, the interconnectors between the UK, France, Belgium and the Netherlands pose a grid outage risk, according to National Grid sources, as a failure on any of them could trigger a chain of events similar to the 9 August power cut.
That is why the company reportedly limits usage of each interconnector to just 750MW during periods it judges to be high-risk.
[Edited by Zoran Radosavljevic]