How the Scheme Works
The idea behind the Scheme is simple.
Precipitation in the form of snow and rain falls in the catchment area of the Scheme. A catchment area is any part of the land where water drains to the lowest part.
Water from melting snow and rain is collected and stored behind dams in lakes and reservoirs and then diverted through tunnels and pipelines down to power stations, hundreds of metres below. Mountainous regions are ideally suited to the generation of hydro-electricity, because there is plenty of rain and snow, low temperatures meaning less evaporation and high mountains to provide the steep fall that is needed for the water to spin the turbines.
In its simplest form, electricity is generated by rotating a magnet inside a wire coil. In a power station, this process is enhanced; the magnet is an electro-magnet or “rotor” spinning inside the fixed coils or “stator” of the generator. Each generator is mounted on a vertical shaft above the turbine and water is used to drive the turbine, which operates the generator. Transformers boost generated voltage to a level that can be economically transmitted over long distances by transmission lines to the towns and cities of eastern mainland Australia.
The amount of electricity able to be generated depends primarily on the distance the water falls (head) and the volume of water (flow) regulated through the turbine.
The type of turbine used is determined by whether the water falls from a high, medium or low head. The Scheme’s power stations use Francis turbines, generally suited to medium heads. Francis turbines have guide-vanes and runners with fixed blades. These guide-vanes control the volume of water required to drive the turbine and thereby determine the amount of electrical power produced.
Once the water has passed through the turbines in the power stations, it is released into rivers to be used to irrigate farms in the dry regions west of the Great Dividing Range.
For more information on the Scheme and how it works, you can buy ”The Power of Water”, a booklet on the Scheme. Check out the Snowy Shop for more details.
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