Sherco 3 to go back online
Thu, 10/03/2013 - 5:47pm admin
By Bill Morgan,
Xcel Energy says the generator damaged by a catastrophic turbine malfunction at the Sherco power plant should be back in service by next week.
In an update filed Sept. 20 with the Minnesota Public Utilities Commission, Xcel wrote that the restoration work on Sherco Unit 3 has been completed, and the unit has undergone tests.
The unit is offline again while workers complete some final work but should return to service on or around Oct. 7, Xcel stated. There will be four days of testing before it is released to start supplying full power.
In November 2011, a turbine malfunction sent parts flying, twisted turbine blades and sparked a fire, putting the largest of Sherco’s three coal-fired units out of commission. Xcel described it as one of the worst mechanical failures in company history.
Xcel initially estimated the unit would be back online in the first quarter of 2013, but the repairs were more complex and took longer than originally thought. Additional damage was discovered during the repair process when workers gained access to hidden layers of equipment and structures.
Unit 3 is the largest of its kind in the United States, and repairing it has been a massive undertaking. The unit had to be dissembled, and some components had to be sent off site for repairs.
Xcel and its 1.2 million Minnesota electric customers will benefit from the return to service. During the shutdown, Xcel said it has spent $64 million to replace the power, which was added to customers’ bills via the fuel adjustment line.
The Southern Minnesota Municipal Power Association (SMMPA), which owns 41% of the Sherco unit, also was forced to buy replacement power, but it absorbed the extra cost, said spokesman Dan Hayes.
The massive project required rebuilding the unit’s turbine, generator and other components. In March, Xcel said it had spent $146 million on the repairs, much of which will be covered by insurance.
In its statement to state regulators, Xcel said it is continuing to work with its insurance provider to identify the cause of the turbine failure.
Xcel has said that an investigation found extensive cracking in one row of turbine blades at their attachment points. The utility’s report attributed the cracks to “stress corrosion” and said the problem was “a function of the original design,” not how the plant had been operated. The blades had been in use since 1999.
No one was hurt in the accident.
Two or three times per day, trains 115-cars-long filled with coal from Wyoming and Montana are unloaded next to the plant in two separate piles.
There are three units at the 2,222-MW Sherburne coal plant - the 680-MW Unit 1 built in 1976, the 682-MW Unit 2 built in 1977 and the 860-MW Unit 3 built in 1987.
Sherco Plant Director Ron Brevig told the Citizen there were no staff reductions due to the incident two years ago. During the Sherco 3 restoration project, Sherco had an additional 150 people (at the peak of restoration activities) working on the restoration (mainly contractors). With the restoration project complete most of those contractors have since moved on to other projects.
Sherco currently staffs nearly 350 fulltime employees and due to a few early retirements this past year, plan to do some ecternal hiring in the near future.