by: Mark Fritsch, General Manager
It has been over a year since the Sherco 3 failure occurred. Unfortunately the unit is still being worked on, however replacement energy charges have been very low, so the financial impact hasn’t affected our electrical rates. Since eighty-five percent of the electricity we receive from SMMPA is generated by Sherco 3, it could have had a significant impact on us.
The badly damaged electric generating turbine in Becker, Minn., is turning out to be harder than expected to repair. Xcel Energy Inc., the Minneapolis-based electric utility that co-owns and operates the massive machine, said that it’s uncertain when repairs will be finished, though it expects it will be this year. A major reason for the delay is because repair work on the generator needed to be redone. That work involves replacing or “restacking” about 400,000 small metal plates in the generator. The initial results were outside the margin of error of 1/32nd of an inch.
The repair work first required raising the giant generator from its horizontal position, a job that took weeks of planning, two weeks to set up the lifting equipment and two days for the actual lift. After placing the 400,000 plates, the unit was set down again. Then the process was repeated after the problems were discovered. Xcel discovered misalignment on the metal plates when they set it horizontal. It needed to be within exact tolerances.
The accident on Nov. 19, 2011, at the coal-fired Sherburne County (Sherco) Unit 3 ripped turbine blades off their mountings, hurled twisted shards and other metal out of the machine, bent an 80-ton rotor and triggered a fire. Fortunately no was hurt. The unit has been shut down since.
Last fall, Xcel said it believed the work would be finished in the first quarter of 2013, but that timetable has been scrapped.
The analysis of the cause of the accident is still being reviewed by forensic experts, including insurance industry consultants. I am being told that the findings should be released in the not-too-distant future.
