Substation Transformer Replacement Project

Substation Transformer Replacement Project

Project Manager

Curt Schmidt, Generation and Transmission Superintendent

What We're Doing

The Stillwater Electric Utility (SEU) operates eight electric substations. This project will focus on transformers located at three of those substations that have reached the end of their reliable service life and are in need of replacement. These transformers are the oldest in the fleet having been installed between 1967 and 1975.

Anticipated Milestones

  • Anticipate Date (Design): Completed

  • Anticipate Date (Construction): Boomer Lake Substation : March 11, 2019

  • Anticipated Date (Completion): Hospital Substation : June 2020

Taking into consideration funding constraints, scheduling substation outages, and the long lead times for delivery of equipment, staff anticipates that the project will be completed in late spring of 2020.  The project will be executed in three phases:

  • Phase One: Boomer Lake Substation. Began construction March 12, 2019 with expected completion in the late May of 2019. 

  • Phase Two: Industrial Substation. Scheduled to begin in the early fall of 2019 with expected completion in the late fall of 2019.

  • Phase Three: Central Substation. Scheduled to begin in the late fall of 2019 with expected completion in the early spring of 2020.

  • Phase Four: Hospital Substation. Scheduled to begin in the early spring of 2019 and expected to be completed in the late spring of 2020.

Project Benefits

Increase in capacity: The three substations each house two transformers that have ratings ranging from 14 Million Volt-Amps (MVA) to 20 MVA.  The MVA rating can simply be explained as how much power the transformer can supply to the distribution system for use by the customers.

Standardization: With the transformer replacement project staff is standardizing on a single transformer manufacturer.  Standardization of this large equipment is an essential part of an efficiently run system, especially with the very unique equipment associated with each transformer. 

Budget & Funding

Project Management


  • 03.11.2019: Sayers mobilized to Boomer Lake Substation site and began work. 

  • 03.27.2019: The construction contractor has completely removed the two 20MVA power transformers from the project site and has begun making preparations for the new transformer to arrive in May.

  • 05.13.2019: Preparations for the new transformers and associated circuit breakers has been completed.

  • 05.25.2019:  Both new transformers are on their pads. They have been assembled, tested, and are ready to be connected to the system. It is anticipated that the new transformers will be energized in late June upon final assembly of the substation.   

  • 07.03.2019:  Construction was completed and the new transformers were energized on June 28, 2019 for Phase I (Boomer Lake Substation).  Boomer Lake Substation is now in normal operation.

Actions Authorized by Stillwater Utilities Authority (SUA)

  • 03.12.18 I SUA-18-10 I Substation Transformer Replacement Project approval

  • 08.27.18 I SUA-18-34 I Bid recommendation for 6 transformers from Pennsylvania Transformer approved

  • 12.17.18 I SUA-18-41 I Bid recommendation for the construction contractor services to Sayers Construction, LLC at Boomer Lake Substation approved

  • 08.19.19 I SUA-19-32 I Emergency purchase of an additional transformer from Pennsylvania Transformer to replace failed transformer at Industrial Substation was approved.

  • 09.09.19 I SUA-19-33 I Bid recommendation for the construction contractor services to the Brandt Companies, LLC at Industrial, Central, and Hospital Substations approved.


May 14, 2019: Stillwater Electric Utility received one of the two substation transformers replacing older versions at the Boomer Lake substation Tuesday. The second transformer will arrive later this week. This transformer is the first of six substation transformers ordered to replace aging transformers at other distribution substations.