Want to know how the power facility in Churchill Falls creates energy? Read on.
In lakes west of the Churchill Falls Generating Station, water reservoirs have been created using a series of 88 dikes totalling 64 kilometres in length. Reservoirs include the Smallwood Reservoir, West Forebay Reservoir and the East Forebay Reservoir. Beyond the reservoirs is Churchill Falls, which features a drop in elevation of 75 metres. The generating station harnesses the energy found in the water reservoirs and Churchill Falls and converts it into electricity.
Controlling the Flow of Water
Water from the East Forebay Reservoir is carried through 11 intake gates and 11 penstocks (large pipes) leading to an underground powerhouse. The intake gates and penstocks help control and direct the flow of water to the turbines.
The intake gates are joined by concrete piers and a common concrete deck, and are opened and closed by a wire rope hoist. During filling and emptying of the penstocks, air is vented through vent housings above the intake deck. Safety devices are provided to prevent opening of the gate beyond the crack-open position before all the air is out of the penstock.
Turning the Turbines
The wicket gates separate the penstock water from the turbines and act as a valve controlling the flow of water to the turbine. Once the water is allowed past the wicket gates, the force of the water turns each of the 11 turbines, located in the massive underground powerhouse (almost 300 metres in length). The turbines are connected to the generator by a common drive shaft. As the turbine turns, so does the generator which makes electricity by spinning a magnet (the rotor) inside of stationary coils of wire (the stator).
The speed of the rotation of the turbine and rotor determines the frequency of the electricity. Speed and frequency are controlled by the degree of opening of the wicket gates which will allow more or less water to reach the turbine. The magnitude of the electrical power that is generated is determined by the detailed design of the generator and the volume and pressure of the water flowing through the turbine.
Accommodating Surges in Water Flow
Water moves from the turbines in the powerhouse to the surge chamber, which collects discharged water and directs it back into the river. The surge chamber is also a safety feature of a power plant design. It safely absorbs sudden rises and falls of water pressure during its discharge to the tailrace. The surge chamber is located about 100 feet south of and parallel to the powerhouse cavity.
Converting Electricity into a Higher-Voltage Current
The electricity leaves the generator at about 15,000 volts and is directed to the transformer gallery. The transformer gallery accommodates 11 transformers. The gallery is located approximately 60 feet north from and parallel to the main powerhouse cavity. These transformers convert the electricity from 15,000 volts to 230,000 volts. The electricity is then directed to the switchyard where it is further transformed to 735,000 volts. That electricity is then sent by means of power lines to the public.
Transmitting Electricity to Market
Three 140 mile-long, 735 kV transmission lines connect the Churchill Falls switchyard to the Hydro-Québec intermediate switching station, Montagnais. One hundred and twenty-six miles of the lines are on Newfoundland and Labrador soil and are owned by Nalcor Energy Churchill Falls.
Supervising Operations using the Control Room
Because of the physical size, complexity and the amount of equipment in the power plant, it is impossible to check the status of all equipment with the frequency necessary for close control. Therefore, the critical control systems have been centralized in a control room so staff can observe the operations of the entire power plant. This is accomplished by recording and indicating instruments, an annunciator system and a computer system.
Responding in an Emergency
Nalcor Energy Churchill Falls has developed a comprehensive response plan to provide guidance and contingency processes in the event of an emergency. The plan is based on consideration of adverse events that each area might be subject to in the course of operations such as fire, explosion, equipment failure, and natural events such as floods and ice storms.