News Flash

Innovative Field Repairs Save Waukesha Customer Significant Money and Time

Blocks Blocks 2
Initial photos of clamping blocks out of position.
Blocks 3 Blocks 4
Repairs in process. Jack being utilized to open space for insertion of high voltage (HV) blocking (top photo). New HV winding shim material installed (bottom photo).

August 30, 2011 – Oncor Electric Delivery, a regulated electric distribution and transmission business delivering power to approximately 3 million homes and businesses throughout Texas, recently relocated an older Waukesha® transformer within one of its major substations just north of the Dallas-Fort Worth airport. After the move, Oncor personnel performed an internal inspection and found a significant amount of dislodged blocking material and coil spacers. Displacement of these components compromised the coil assembly’s critical clamping system which placed the transformer at great risk for operational failure, especially if subjected to any type of through-fault event.

Recognizing the potentially hazardous situation, Oncor personnel contacted Waukesha for repair options. Troy Kabrich, service and components division general manager, quickly devised a unique plan that would allow our service team to repair the transformer on-site rather than move it to an off site repair facility. This solution would save the customer over $250,000 and weeks of repair time while eliminating the possibility of causing further damage to the unit during transit.

Upon receiving the order from Oncor, Waukesha engineers in California, Prat Seesurat and Raj Ahuja, immediately pulled design information for the Milpitas-built transformer and developed a bill of materials for all types of insulation that could be needed for the repair.

Steve Berry, field project manager, and Troy worked together to specify and configure specialty field equipment required to complete the project. Additionally, Troy handled the procurement of all insulation packages from Weidmann Electrical Technology (, coordinated with Waukesha South to put these items through vapor phase in preparation for installation and worked with Steve to inventory and organize the tool trailer that would play a critical role on-site.

Once vapor phase processing was complete, a team of field service technicians—including Steve Nickels, Paul Kent, Mike Cheney and Dennis Goodrich—were dispatched to the job site. The crew faced challenges inherent in performing intricate coil repairs such as carefully removing clamping pressure to enable resetting of the blocking and spacers in a tight space with limited mobility. Extreme temperatures (ambient temperatures of 105°F and internal tank temperatures up to 140°F) added another level of complexity to the working conditions. To combat the potentially damaging heat and humidity inside the transformer, Waukesha personnel utilized a closed loop 20 ton air conditioning and dehumidification unit throughout the repair process. They replaced nearly 20% of the high voltage coil blocking, verified the other 80% was properly located and made design modifications to the blocking system at the top pressure plate in each “core window” (the open space between the core limbs) to prevent a recurrence of the dislodging issue.

Meticulous planning and craftsmanship by the Waukesha team resulted in completion of the job four days ahead of schedule. Following conclusion of the project, Mike Hamilton, senior manager of engineering at Oncor, provided the following comments:

"Good work, Troy. We appreciate the thoroughness of this (service) report and the work performed on this unit. Seeing how loose the blocking was, it is apparent to me that a close-in through-fault might have been the demise of this large transformer. We appreciate the estimate on the schedule that you provided and the efficiency by which you followed it. Thanks for working your plan and delivering the repair ahead of the time estimate that you provided to us."

Reblocking is a highly specialized repair which few companies have the ability or equipment to complete in the field, and our team performed the job flawlessly. Congratulations to everyone on the field service crew involved in this first-of-its-kind project for Waukesha! And thank you for giving us another great example of delivering the Waukesha Experience by providing value to a customer through innovative technical solutions, teamwork, expertise and experience.


Experience Waukesha