15-week transformer makeover for Duke Energy ‘a miracle’

When a 46-year-old GE transformer at Duke Energy’s W.C. Beckjord Generating Station Unit 5 failed, Duke corporate engineer John Flick pressed into service a 40-year-old spare transformer of questionable reliability, and sought options. A new transformer was not an option, as Flick needed a fast solution.

ABB’s TRES (Transformer Remanufacturing and Engineering Services) organization, however, delivered just the option he needed. ABB TRES offered to redesign and upgrade the failed transformer by replacing the necessary components to make it new and reliable again – in only 15 weeks.

Beckjord is a 1,124-megawatt coal-fired power plant near Cincinnati. The plant is located in the ReliabilityFirst region. The mission of the ReliabilityFirst organization is to preserve and enhance electric service reliability and security for interconnected electric systems within its geographic area, which spans 13 states and the District of Columbia, encompassing mainly the Mid-Atlantic and central areas of the United States, representing nearly 40 percent of the eastern interconnected electric network.

So, Flick needed to provide reliability.

ABB goes to the archives
Since ABB owns the original drawings and manufacturing information for more than 70 percent of the transformers operating in North America, the ABB TRES team quickly retrieved the Beckjord Unit 5 transformer’s original drawings and manufacturing details from the archives. With this information, transformer service experts explained to Flick exactly how the transformer could be remanufactured to fully take advantage of ABB’s TrafoStar technology. The technical knowledge and experience of the ABB TRES team put Flick at ease.

As soon as ABB TRES received Duke’s purchase order, the redesign began. Using the transformer’s original drawings, the ABB TRES team had performed the redesign, ordered materials and started production of new components by the time the transformer reached the ABB TRES factory in St. Louis, Mo.

The 260-megavolt-ampere (MVA), 55-degree Celsius step-up general service unit was rated 132 kilovolts (kV) on the high side and 20.9 kV on the low side. During the remanufacturing process, it was upgraded to 291.2 MVA, 65°C. The transformer tank was refurbished and used, as was the control cabinet. The original five-legged electrical steel core was also cleaned and qualified for reuse. Current transformers were rewired and qualified for reuse. In addition, two conservator tanks were refurbished and new air cells were installed.

All other components were replaced. The ABB staff specified the windings, pressure plate assemblies, core insulation, bushings, de-energized load tap changer, cooling system, controls, buss bars, piping, gauges, oil pumps, valves, gaskets, junction boxes, conduit and wiring.

The transformer on arrival in St. Louis.

ABB TRES did, however, encounter one issue with delivery time on replacement low-voltage bushings.

Help from Alamo
The bushings that were originally selected had a 36-week delivery time. That was when ABB’s transformer components division in Alamo, Tenn., stepped in and found an upgraded bushing type that fit Duke’s needs and could accommodate the aggressive remanufacturing schedule. These low-voltage bushings were ordered and arrived in six weeks.

When assembly was complete, ABB TRES tested the transformer on its test floor in St. Louis to ensure that no defects were present and the up-rated transformer would perform as designed. All performance expectations for the new transformer were met or exceeded during the testing process.

When Flick came to St. Louis for an inspection, the transformer was almost unrecognizable. The old components had been removed, the rusted tank had been cleaned and coated, and the new components were being installed.

A miracle
“ABB performed a miracle,” Flick said.
ABB TRES project manager Ken Dugger was able to show Flick physical distortions in the old windings and a turn-to-turn failure in one low-voltage winding with considerable erosion of the conductor and copper contamination throughout the coil.

Since all organic materials susceptible to aging were replaced with brand-new materials, the remanufactured transformer would be expected to have a life expectancy equal to, or greater than, a new transformer. The remanufactured transformer came with a warranty that lasts 36 months from the time the transformer was assembled on site.

This remanufacturing project not only saved Duke Energy time and money, it also contributed to their environmental and sustainability leadership. The recycling of the transformer’s core steel and main and conservator tanks aided in minimizing Duke’s environmental footprint by avoiding the use of raw materials and the energy needed to produce these steel components.

ABB TRES also provided Duke with relocation and installation services. The transformed transformer was shipped back to Duke Energy – arriving at the Beckjord plant just in time for a planned outage.
For more information, visit www.abb.com.