Energy giant SSE is to pay a record £33m fine after breaching licence conditions.
Ofgen has ruled that the wind farm operator has been charging excessive prices to cuts its power output when the national grid is being overloaded.
Costs for consumers have been pushed up as a result, the regulator said.
The Beatrice wind farm, one of Scotland’s largest, has agreed to pay the fine.
SSE own 40% of the farm and operate the facility on behalf of Beatrice Offshore Windfarm Limited (Bowl).
Eight miles off the Caithness coast, Beatrice boasts 84 turbines and is capable of powering nearly half a million homes.
Ofgem said in a statement: “Ofgem has been clear that electricity generators must put in place controls to ensure that their prices are set in a way that ensures that they do not obtain excessive benefits during the periods where they are required to reduce output due to the limitations of the transmission network.
“If they fail to do so, they should expect to face large penalties.”
A spokesman for Bowl said: “Beatrice Offshore Windfarm Limited accepts that it breached one of its electricity generation licence conditions. The breach was in Bowl’s view wholly unintentional.
“Bowl will make a payment to the Ofgem consumer redress fund, has reviewed its bid pricing policy and fully cooperated with Ofgem throughout to conclude this process.
“With other industry participants, Bowl is engaging on proposed modifications to the relevant industry code and Ofgem’s ongoing consultation on its approach to interpreting and enforcing the transmission constraint licence condition.”
Bowl’s fine is the fifth handed out by Ofgem for the offence and £10m more than the previous highest.