Wisconsin Power and Light, Wisconsin Public Service Corp. and Madison Gas and Electric applied July 21 at the Public Service Commission of Wisconsin for a Certificate of Authority to replace two generator step up transformers at the Columbia Energy Center in Pardeeville, Wisc.
The existing generation step up (GSU) transformers on the coal-fired Columbia Units 1 and 2 are, respectively, 40 and 39 years old, and are demonstrating signs of deterioration.
The Columbia Energy Center (Columbia) consists of Unit 1 and Unit 2. Each unit has a tangentially-fired boiler, an associated generator, and a generator step up transformer. Columbia Unit 1’s GSU transformer is referred to as GSU 1, and Columbia Unit 2’s GSU transformer is referred to as GSU 2.
“The GSU transformers in service are showing increasing signs of age related deterioration and stress from continuous operation experienced over their service lives,” the application noted “This deterioration is identified through dissolved gas analysis of the transformer oil and increased maintenance requirements of the units. The Applicants are proposing to replace two GSU transformers during planned outages in 2016 and 2017.
Columbia Units 1 and 2 began operation in 1975 and 1978. The nameplate generating capacities for Units 1 and Unit 2 are 512 MW and 511 MW respectively.
GSU transformers are utilized for both Columbia Units 1 and 2 to convert the electrical voltage and current output from the generators to levels needed for transmission. The transformers operate continuously anytime power is generated for transmission and are showing signs that they are approaching their end of useful service lives.
The major components of the replacement project are:
- Removal of the existing GSU 1 and GSU 2 transformers.
- Installation of new foundations.
- Extension of the existing oil water separator system to the new foundations.
- Installation of new GSU transformers.
- Extension of the isolated phase electrical bus work to the new transformer locations.
- New underground conduit and cable to the foundations for auxiliary power and control system cable routing.
- New cables routed to the energy management system/system control and data acquisition systems along with modifications to the distributed control system programming for monitoring and controls.
- Relocate the fire suppression system to the new GSU transformer foundations.
The utilities are proposing to install the new GSU transformers during the planned outages for a turbine upgrade project. The installation of GSU 2 will occur during the first quarter 2016 planned outage for Unit 2, and the installation of GSU 1 will occur during the first quarter 2017 planned outage for Unit 1. The total project cost is estimated at $15.2m.