The last of three new gas-insulated transformers is being installed at the Bagnell Dam plant of Ameren Missouri this week, making the Bagnell Plan the first and only electricity generating plant in North America to use the environmentally friendly units.
While that may not sound like a big deal to the layman, it's something that has made Bagnell Dam plant officials quite proud and something that has moved Ameren Missouri to the forefront in environmental leadership.
Other electricity generating plants around the world have installed the gas-insulated transformers — especially in the Far East — but the Bagnell plant has the honor of being an industry leader in the United States.
The vast majority of transformers, regardless of size, are mineral oil-insulated to insulate live parts of the transformers. The oil helps cool the inside of the transformer to prevent overheating of the equipment and parts. Most of the plant's transformers are 80 years old, though the oil inside them has been changed a few times over the last eight decades.
At the time of the replacement project, there were about 72,000 gallons of insulating oil in the aging transformers. The oil has been removed from the old transformers and is being temporarily stored until being sold for recycling.
Regular monitoring of the transformers a few years ago found that the electrical insulation was degrading, which increases the likelihood of a failure. Such an unlikely scenario could dump thousands of gallons of oil into the Osage River, causing an environmental nightmare.
During discussion about replacing the aging oil-insulated transformers, plant maintenance supervisor Jim Lueckenhoff — formerly at the Callaway Nuclear Plant — said the Callaway plant had investigated using an innovative new type of transformer made in Japan that was insulated with an inert, non-combustible gas. He thought that technology might fit the Osage application.
After extensive research, the Osage Plant elected to replace the old oil-insulated units with gas-insulated units. The inert gas used is SF-6, sulfur hexafluoride, which has good electrical insulating properties, and the transformer itself also has a smaller footprint compared to the oil-insulated units, according to Alan Sullivan, consulting engineer at the Bagnell Plant.
Plant Superintendent Phil Thompson said the goal was to replace the older transfers by 2014, and that is being accomplished with several months to spare. The first was installed in 2010, the second last year and the third this year. The original units lasted more than 80 years, and officials estimate the new transformers will have a lifespan of between 30 and 50 years.
Ameren Missouri employees have worked 12 hours a day, six days a week for about two weeks to assemble the transformer, which arrived on semis.
The dynamics of the gas-insulated units fit the physical limitations of the Bagnell Plant and also the long-term environmental objectives.
Page 2 of 2 - "Ameren is very environmentally proactive and must meet numerous environmental regulations," noted Sullivan. "We recognized the possibility of a fire or an oil leak that if it reached the (Osage) river would be very serious. Meeting these environmental regulations is very expensive. These enhancements to meet environmental regulations go into the rate base, and result eventually in higher electrical costs. It is a debated point: Is the public willing to pay higher costs for electricity in order to meet the ever-changing and restrictive environmental regulations?"
Thompson said none of the federal agencies that regulate or oversee Ameren or the Bagnell Plant has pressured the company to install the more environmentally friendly gas-insulated units, but the liability of an environmental accident justified the additional expense.
The new transformers were purchased from Toshiba and were manufactured in Japan. Transformers of this type are not manufactured in the United States because the high population density in Japan as forced the Japanese to design transformers with smaller and more efficient units. Once the decision was made to replace the aging units, Lueckenhoff led the construction effort. A representative of Toshiba, the Japan-based manufacturer, spent several weeks at the Lake of the Ozarks supervising installation of each of the new units.
Sullivan's grandfather Elmer Sloan and his uncle Lloyd Sloan were involved in Bagnell Dam's construction.
"I think it's cool that they were here to see the original transformers installed, and now I'm here to see them go out," Sullivan said.