The first rebuilt generating unit at the Hydropower Station Rehabilitation has returned to service. After months behind a cofferdam, the unit was rewatered, tested and released back to the station operator, and it is again sending power to the grid. Three more units will follow, one at a time.
Rebuilding a machine inside a dam
Each of the station’s four units was more than 70 years old. To rebuild one, our crews first isolated it from the river with stoplogs and a cofferdam, then pumped the water passages dry. Instruments watched seepage and structural movement throughout, and the dewatering plan had backup pumps on standby every hour of the outage.
Inside the dry unit, the work was heavy and precise. The powerhouse crane, refurbished and load-tested at the start of the program, lifted out the old rotor and turbine runner. New components were set to tight alignment tolerances, the generator was rewound, and new governors, excitation and controls were installed and wired.
Proving it before release
A rebuilt unit is not finished until it proves itself in the water. Before release, our commissioning team, working with the owner and the equipment suppliers, carried out:
- Watered-up checks of seals, bearings and cooling water.
- Balancing runs at increasing speeds, with vibration measured at every bearing.
- Generator tests, including synchronization to the grid.
- Load rejection tests, dropping the unit off line at load to prove the controls respond safely.
- Training sessions with station operators on the new controls.
The river does not care about our schedule. We planned every outage around its flows, and the first unit came back on the day we said it would.
Project manager, PerryWester
Three to go
The next unit is already isolated and dewatered. Because only one unit is ever out of service, the station has kept generating through the program, and environmental and fish passage rules have been met at every step. Our thanks go to the station operators, our trade partners and every crew member working inside the dam.
