Northern States Power d/b/a Xcel Energy (NYSE: XEL) is sticking with its position of the last few weeks that the 884-MW Sherburne County (Sherco) Unit 3 will be back in service in early September after being down since November 2011.
Northern States Power told the Minnesota Public Utilities Commission in a July 26 update: “We continue to make good progress on our restoration efforts and continue to expect Unit 3 to return to service in early September. Once returned to service, there will be a short period of testing (likely a couple of weeks) to complete testing, tuning, and ramping before releasing the unit for dispatch by MISO.”
In its last update the company indicated that it had received the final root cause analysis report on the mechanical problems that led to a fire that shut the coal-fired unit.
“We continue our detailed internal engineering examination of the 500+ page report and are implementing a plan to review the report with our internal stakeholders and senior executives by mid-August,” the company noted. “We anticipate releasing the report in early September when our communication and review process has been completed.”
The 884-MW Unit 3 went off-line in November 2011 while being restarted after a repair shutdown. During the testing procedure after unit restart, specifically the overspeed test, the turbine and generator instrumentation showed vibration levels significantly above normal, and the unit was shut down. The vibration damaged many of the steam, oil, and hydrogen seals in the turbines and generator, and caused a fire.
Sherco is a three-unit, 2,400-MW plant. It burns low-sulfur Western coal from mines in Montana and Wyoming. The plant normally burns more than 9 million tons of coal a year. Notable is that Northern States Power, after doing a life-cycle study of Sherco Units 1-2, has said these units are viable for the long-term future.