London Array's general manager, Mike O’Hare revealed a Siemens 3.6MW turbine was inoperable for 100 days from June following gearbox issues.
London Array Limited, a consortium of Dong Energy, E.on and Abu Dhabi investment company Masdar, is responsible for the operation and maintenance of the 175 Siemens SWT-3.6-120s, which lie 20 kilometres off England's Kent coast.
Speaking at Windpower Monthly's offshore operation and maintenance forum, O'Hare said: "It took 100 days to be changed and that was not good enough.
"I have high expectations of the wind farm. One hundred days is not untypical and I understand that’s good for other projects but I think it could have been done quicker.
"We’re working with our service providers, Dong and Siemens, to improve the speed of any future repairs."
In response, Siemens chief technology officer, Henrik Stiesdal, said: "Deviations in condition monitoring signature have been observed [with the gear box]. The gearbox was replaced to carry out a full root cause analysis.
"The actual timing of main component replacement offshore is a function of several factors, including on-site inspections, vessel availability, work preparation, weather, and synchronization with other activities. Unfortunately we cannot provide details of the actual case."
London Array Ltd has just been handed official responsibility for the site. O’Hare said: "The whole joint venture from London Array has been handed to me. It’s a challenge, and it won’t be easy, but I look forward to it."
Work started on London Array in 2010 with the first power generated in October 2012, several months behind schedule, at a cost to Dong Energy.
In January 2012, shallow water forced another delay to the development. UK prime minister David Cameron officially inaugurated the project on 4 July.