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Exelon explains turbine collapse

HURON COUNTY – Representatives from the companies responsible for the turbine that collapsed Feb. 25 in Oliver Township said they’ve discovered the cause and taken measures to ensure it never happens again.

Mark Van Diepenbeek, senior operations manager for Vestas Americas Great Lakes Region, the turbine’s manufacturer, said three factors came into play to create the perfect storm that caused the turbine to spin too fast and eventually collapse.

First, each blade had worn seals on the cylinders in the pitch system, which enables to blades to turn so they’re not catching the wind.

Second, the hydraulic brake intended to slow the turbine during an overspeed event failed.

Third, there was an actual storm. Wind speeds exceeded 20-meters per second, or around 45 miles per hour.

“The thing just basically shook itself apart,” he said.

Diepenbeek said his company is in the process of inspecting the pitch system cylinders in all its turbines and is replacing any that show signs of wear.

“So far in our inspections, we haven’t found more than one cylinder with wear. … That leaves two good cylinders, and we are 100-percent confident that one good cylinder will be enough,” he said. “Aerodynamically, it’s not possible for the turbine to overspeed as long as one blade is not able to move.”

Exelon Generation spokesperson Kristen Otterness said the wind energy company is committed to preventing similar problems in the future, and changes have already been implemented throughout its fleet.

Diepenbeek said the company has increased turbine monitoring and added software to prevent the hydraulic pump from shutting off in a similar scenario.

Also, the company has updated software to alert wind park owners of a possible problem and has shared what it learned from the incident with the wind energy industry, so wind parks throughout the world will be safer.

He said the optimum speed for the eight-year-old turbine is 14.4 rotations per minute, which equates to a tip speed of approximately 200 miles per hour and a generator speed of 1,212 rpm. When the turbine collapsed, the blades were had hit 18 rpm.

“The generator at that speed would be running at 1,212 rpm, and for the blades to go another three rotations per minute, that’s another 300 rpm. It’s quite a bit,” he said.