10 power generators will be replaced
By Dean Brickey
The U.S. Army Corps of Engineers has started an immense project at McNary Dam that will take many months and many millions of dollars to complete.
Using two huge cranes, employees of Andritz Hydro started the heavy lifting late last week. It took them 2-3 hours to expose the various components of two giant generators. Workers will start replacing worn electrical components in a few weeks.
Andritz Hydro is an Austrian firm with significant experience in hydroelectric plants. Its workers will replace the stator, the part of the generator where power is generated. The new copper wire coils or windings comprise more copper and less – but better – insulation, said Bruce Henrickson, a Corps of Engineers spokesman in Walla Walla.
He said Andritz will perform the work on 10 of the McNary Dam’s 14 generators. The project will take five years, concluding in 2015.
Henrickson said the project is necessary to improve reliability and to increase future power generation output.
“The generators are at end of life,” he said. “Some have already experienced failures.”
Congress authorized McNary Dam in 1945. Construction began in 1947 and concluded in 1954. All 14 power generators were operating by 1957.
Four generators have failed since.
“We’ve only replaced two other of the 14 generator stator windings since the dam was built,” Henrickson said. “Those were replaced in the past dozen years after those two generators failed.”
The stator windings being replaced are more than 50 years old. And the timing for replacing the windings is critical.
“We’ll replace two of them during low-flow months from July through December 2010,” he said. “Then we’ll replace two stator windings per year during the July-December low flow window between now and 2015.
Andritz Hydro has a crew large enough to work on two units at once.
“Generally, one unit will lag in progress a few days behind the other,” Henrickson said. “At any given time there is work being performed in two units.”
The workers remove the copper coils from slots in the generator’s stationary core, which holds the windings. Workers inspect, prepare and paint them with semi-conductive paint. Technicians then place new pre-fabricated copper bars in the slots along with temperature sensors and packing materials to keep the copper bars from moving under generator vibrations. Others braze the bars together to form the coil connection.
Bonneville Power Administration is funding the McNary project because of its impact on regional power. The cost of the five-year contract is nearly $64 million, including $20 million this year.
Because the work is being done during the low-flow period of the year, there’s little impact on power production by having two of the 70-megawatt generators offline for five or six months, Henrickson said.
No significant investments have been made to improve the efficiency of the generating units since they were installed.
The powerhouse has 14 of the 70-megawatt hydroelectric generator units – a 980-megawatt powerhouse capacity. One megawatt serves approximately 700 homes. At full capacity, McNary’s powerhouse can supply enough power for about 686,000 homes. During fiscal 2009, McNary Dam produced 5.1 billion kilowatt hours of electricity.