UK’s National Grid says lightning caused nationwide power blackout

A blackout in Britain which cut power to one million customers and caused transport chaos on August 9 was owing to a lightning strike, the grid operator said in a report to regulator Ofgem, which said yesterday it would investigate the matter further.

Ofgem commissioned the report into the causes of the power cuts from National Grid. It said it would open its own investigation to establish whether any of the grid and network operators or generators breached their licence conditions.

“Having now received National Grid’s interim report, we believe there are still areas where we need to use our statutory powers to investigate these outages,” said Jonathan Brearley, Ofgem’s executive director of systems and networks.

“This will ensure the industry learns the relevant lessons and to clearly establish whether any firm breached their obligations to deliver secure power supplies to consumers.”

Ofgem’s powers under the Electricity Act, which it will use to conduct the investigation, allow it to impose penalties up to a maximum of 10 per cent of the regulated companies’ UK turnover.

National Grid reported annual revenue, or turnover, of £14.9 billion (Dh66.17bn) for the year to March 31, 2019. An hour-long blackout on the evening of August 9 cut off one million electricity customers, including homes, businesses, one hospital and Newcastle Airport and caused disruption on the rail network.

National Grid said the power cuts were the result of an unusual issue that led to the almost simultaneous loss of output from two generators – Orsted’s Hornsea offshore wind farm and RWE’s Little Barford gas-fired plant.

There were many lightning strikes that hit the electricity grid that day, but only one had a significant impact – on a transmission line at 16.52 local time, which returned to normal operation after about 20 seconds, the grid’s report said. About 500 megawatts of generation capacity was also disconnected – all of which is normal for such events.

However, immediately after the lightning strike and within seconds of each other, Hornsea and Little Barford reduced supply to the grid, disconnecting 1,378 megawatts of generation.

“As generation would not be expected to trip off or de-load in response to a lightning strike, this appears to represent an extremely rare and unexpected event,” National Grid said. It added it will deliver its final report to Ofgem by September 6, in which it will examine the exact failure mechanisms as well as demand-side impacts and communication processes.