Extreme winds topple turbine -- Twice in two months for Gamesa

Storm force winds with gusts claimed to be as high as 55 metres per second (m/s) tore the nacelle, rotor and two tower sections from a 660 kW Gamesa Eólica G-47 turbine at Palencia in the Spanish province of Castile and León in early January. The incident happened at the 19.8 MW El Pical plant, currently being built, and was the second of two Gamesa turbine failures in two months in the region. In December in Merindades, a G-47 tower was fractured, apparently struck by a blade and again in high winds, though Gamesa declines to comment further on this incident.

The nacelle was removed the day after the incident by the owner, Corporación Eólica SA (CESA), the wind developing arm of Spain's Guascor Group, according to the company's Alvaro Maortua. CESA owns both the damaged wind turbines.

According to Gamesa's Alvaro Viladrich, neither turbine was receiving power from the grid at the time of the incidents, though at Merindades the wind farm had been on-line for at least two months, confirms the regional industry department. Without electricity, the El Pical unit's control system was out of operation and although the turbine was parked to cope with the site's prevailing winds, the storm came from the opposite direction. These were, "Extraordinary circumstances which could not have been foreseen," says Gamesa.

According to wind data collected on site, the ten minute wind average was about 42 m/s, gusting to 49 m/s. Gamesa says, however, that the anemometer loses precision after 25 m/s and that wind sheer on the hilly site would not have been registered. The company further points out that the El Pical turbine was the only one of hundreds of its turbines in northern Spain that suffered serious damage during the January storm.

The incidents attracted public attention due to a campaign by a new national watchdog group, Mesa Estatal para un Emplazamiento Racional de la Energía Eólica (story left). "It only goes to demonstrate how rushed such developments are and the risks involved in installing turbines on high ridges," states the group. The El Pical turbine is situated at the top of a 60-degree slope, 1500 metres above the village of San Pedro.