However, the Indian manufacturer and project operator Iberdrola Renewables say it is premature to speculate until an investigation is completed.
The companies expect to soon finish their probe into the cause of the accident that sheared the rotor from its power shaft at the 149.1MW Rugby wind farm in North Dakota on 14 March.
But Jerry Lein, a utility analyst at the North Dakota Public Service Commission (PSC), tells Recharge that Iberdrola officials have told him bolt failure was the cause, and the companies have shut down six other turbines after inspections showed that bolts on some of them may need replacement.
As
