The UK government has ordered its own inquiry into power cuts which affected nearly a million businesses and homes in England and Wales on Friday and caused severe transport disruption at the start of the weekend getaway.
New Business and Energy Secretary Andrea Leadsom said on Saturday that she would commission the government’s energy emergencies executive committee to look at the incident after power outages during rush hour caused “enormous disruption”.
Hundreds of people were trapped on trains as a result of the power cuts, which were reported across the South-east, Midlands, South-west and North-east of England as well as in Wales. They also disrupted traffic lights in areas of London and the South-east as well as essential services such as hospitals.
National Grid, which is in charge of Britain’s electricity system, “must urgently review and report to [energy regulator] Ofgem”, Mrs Leadsom added in a tweet.
The energy emergencies executive committee oversees urgent responses and recovery after major power incidents to ensure the country always has a secure supply.
Mrs Leadsom’s intervention came after Ofgem threatened National Grid with a possible fine and demanded a detailed report from the company “so we can understand what went wrong and decide what further steps need to be taken”. This could include enforcement action, the regulator said.
Ofgem has the power to fine energy companies up to 10 per cent of their turnover if they are found to have been at fault. In National Grid’s case, any such fine would only apply to the part of the business that is regulated, a spokeswoman for Ofgem said.
National Grid said on Saturday evening that it would work closely with the government’s investigation “to ensure that learnings can be reflected in industry processes and procedures going forward” and said it had initiated its own internal review.
It had earlier claimed the cause of the power cuts “was not with our system but was a rare and unusual event, the almost simultaneous loss of two large generators, one gas and one offshore wind” at 4.54pm on Friday.
The generators involved were the Little Barford gas-fired power station in Cambridgeshire, owned by the German power company RWE, and the Hornsea offshore wind farm, owned by Danish utility Orsted.
National Grid said other generators had increased their output to compensate for the loss in supply. However, due to the scale of the generation losses this was “not sufficient” so it disconnected selected areas of demand across the country to “protect the network and ensure restoration to normal operation . . . as quickly as possible”.
Duncan Burt, National Grid’s operations director, told the BBC the company was “very confident that there was no malicious intent or cyber attack involved” in the incident.
RWE acknowledged its Little Barford site had experienced a technical fault on Friday afternoon, but said it was back in action and ready to be called upon by National Grid to generate power later that night.
“What is now needed is for National Grid and Ofgem to investigate why the wider system issues occurred,” the company added.
Orsted confirmed that problems had occurred at its Hornsea One wind farm, off the Yorkshire coast, on Friday, adding: “We are investigating the cause, working closely with National Grid System Operator, which balances the UK’s electricity system.”
Such technical faults at power plants are not uncommon but it is rare for two generators to trip at the same time.
The last similar incident was in 2008, when the Sizewell B nuclear plant in Suffolk and the now closed Longannet coal-fired station in Fife went offline within minutes of one another, causing blackouts for hundreds of thousands of homes.
Tom Edwards of Cornwall Insight, a consultancy, said problems can occur when there is an unscheduled outage at one plant “then you have got to change the output at another one and it doesn’t want to do that and it falls over as well”.
Although it caused inconvenience for lots of people, Mr Edwards described Friday’s events as the electricity system doing what it is “supposed to do in those situations”, where National Grid needs to act quickly to avoid a total shutdown of the system and blackouts nationwide.
There would have been “no human being in control of what was happening, all the automatic systems kicked in”, Mr Edwards added.
Some have questioned whether the greater contribution of renewables to Britain’s overall electricity mix could raise the likelihood of such events occurring due to the unpredictability of their output, which is based on weather conditions.
Mr Edwards said renewables such as wind and solar — which accounted for a third of electricity generated last year — do make it more challenging to balance supply and demand across the system but that there is technology, such as batteries, to deal with it.
National Grid is working on a plan to ensure the system is ready to cope with a scenario where 100 per cent of electricity could be generated by zero carbon sources by 2025, he added.
Additional reporting by Janina Conboye.