2025-002 - Mayo B Hydro Unit #2 (MBH2) 10-Year Teardown and Overhaul

In 2025, YEC will be performing a major overhaul on the MBH2 Hydro Unit. A scope of work is included as Appendix 7. This scope of work presented in Appendix 7 outlines desired outcomes of the overhaul as well as general and technical requirements of the site contractor for supplying specialized work, materials and documentation leading up to the site work, during the site work, and at the project closeout stages.

The Mayo B Generating Station, in service since 2011, is located approximately 400 km north of Whitehorse. The Mayo B Hydro powerhouse is located at ground level and serviced by a 35 tonne overhead crane. The turbine floor is accessible via a single storey stairway at the service bay or at the rear of the building. The station has two identical horizontal Francis hydro turbines generators, MBH1 and MBH2, and are designed to output 5124 kW each. They operate under a rated head of 60.93 m and spin at 514.2 rpm. The turbine, manufactured by Chongqing Yunhe Hydro Power Group (CYHPG), is rated at 5309 kW. The generator, also manufactured by CYHPG, has a 5693 kVA rating at 0.90 PF with a 6.9 kV output. The generator has a static excitation system (ABB), is naturally air-cooled and is coupled directly with the turbine. To date, no major overhauls have been performed on the MBH2 unit since original commissioning.