Ofgem found the combined loss of power from the under-construction 1.2GW wind farm off the east coast of England and a 740MWe gas plant, as well as a loss of 150MW of smaller generation at local level had caused a power outage on 9 August last year.
It added the power cut had been caused by unforeseen technical issues and had been quickly resolved.
At the time, Ørsted explained an unspecified “technical fault” had caused the wind farm to rapidly de-load.
It was confident that should the same set of circumstances arise again, Hornsea One “would respond as required”.
On 3 January 2020, a Hornsea One spokesperson said: “In recognition of our role in the outage, we have offered to make a voluntary contribution to Ofgem’s redress fund.
“We have co-operated with Ofgem throughout their investigations and conducted a thorough internal review of the events in order to prevent a situation like this from happening again.”
After carrying out an investigation into the power cut, the energy regulator found most local network operators disconnected and reconnected consumers, as they were expected to do.
However, UK Power Networks (UKPN) began reconnecting customers without being asked to by transmission system operator (TSO) National Grid. This could have potentially jeopardised the recovery of the system, Ofgem stated.
UKPN and RWE have also agreed to pay £1.5 million and £4.5 million into Ofgem’s voluntary redress fund respectively.
Companies can offer to pay into Ofgem’s redress funds in lieu of a financial penalty for a breach of licence conditions, according to the energy regulator’s website. These payments can be used to remedy any harm to consumers, in addition to any compensation to those directly affected, it explained.
Ofgem added that National Grid must adapt to “the complex and changing world it operates in”, and confirmed plans to carry out a review into the TSO’s structure and governance.