Three companies have paid Ofgem a combined £10.5m over the power cuts of 9 August, which disrupted supply to more than 1m customers.
After investigation, Ofgem found that two large power stations, Hornsea One Ltd and Little Barford – operated by RWE – did not remain connected after the lightning strike.
Both companies have agreed to make a voluntary payment of £4.5m each into the regulator’s redress fund.
In addition, UK Power Networks (UKPN) will also pay £1.5m for a technical breach of rules, as it began reconnecting customers without being asked to by the National Grid, which could have potentially jeopardised recovery of the system.
Although this had no effect on the 9 August UKPN has acknowledged the technical error and made the voluntary contribution.
Ofgem said that the investigation has raised questions about how the ESO’s management of the system is carried out.
The watchdog has already announced that it will be conducting a review into the structure and governance of the ESO, and added that the concerns raised in this investigation will inform this work.
It also said it had worked closely with the Office of Road and Rail, which today published its findings into rail companies’ roles in the disruption.
It found that software flaws on some trains caused extended delays for commuters.
Jonathan Brearley, Ofgem’s executive director, said:
“Consumers and businesses rely on generators and network companies to provide a secure and stable power supply. 9 August showed how much disruption and distress is caused to consumers across the UK when this does not happen.
“That is why it is right that companies that were unable to keep generating have paid into our consumer redress fund.
“Our investigation has raised important questions about National Grid’s Electricity System Operator, which is why our review will look at the structure and governance of the company.”