The £17 million investment by renewable energy group Gaelectric is at Monnaboy on Loughermore Mountain close to Eglinton.
Patrick McClughan, head of corporate affairs at the firm, said the opening was a milestone.
“Our total permitted portfolio now stands at 140 megawatts in Northern Ireland and represents a total investment of approximately £170 million.
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“This consolidates Gaelectric’s position as the largest indigenous renewable energy company in Northern Ireland, and we are proud to make a significant contribution to Northern Ireland’s renewable energy targets.
“It is important to Gaelectric that local communities close to the Monnaboy wind farm have the opportunity to share in the social and economic benefits of this renewable energy development.”
He said the farm was capable of meeting the electricity demand of more than 7,400 homes.
In the last four years, Gaelectric has secured planning approval for nine Northern Ireland wind farm developments.
It has sites in counties Antrim and Londonderry and plans to commission its remaining projects within a year.