Getting Water to the Power Station
To produce electricity, a way has to be found to take the water from the storage to the power station.
Water is conveyed to power stations situated near storages through intakes and down vertical shafts and/or inclined tunnels (called power tunnels). Power tunnels are often lined with concrete or steel to prevent leakage of high pressure water into the surrounding rock. A typical intake is fitted with a trash rack and control gates. The steel mesh trash rack prevents rubbish such as logs being carried down into the turbines.
As the water enters the power station it passes through a large inlet valve which can be quickly opened or closed. Each valve opens to a large spiral casing made of steel. These direct the water onto the blades or buckets of the turbine. Water leaves the turbine and flows out of the station via the tailrace.
Intake gate Parangana Dam
Where storages are situated some distances from the power station, channels need to be constructed to carry the water overland.
If the topography is relatively flat open channels are used. There are two types - canals and flumes. Canals are shallow excavations. They are lined with concrete if water leakage would otherwise be a problem. Flumes are rectangular-shaped open channels whose floors and walls are made out of reinforced concrete. They are built where a channel needs to be taken around the sides of a steeper slope and canal excavation presents too many problems.
In some rugged topography it is cheaper to channel the water through tunnels and pipelines. Various combinations of canals, flumes, tunnels and wooden or steel pipelines are features of many of Hydro Tasmania's power schemes.
Canal and Flume in the Bronte area
Above the power station the overland channels feed water into vertical shafts, power tunnels or high-pressure-steel pipes called penstocks. Large towers (called surge towers) are often built near the top of these structures. They are designed to prevent any damage resulting from pressure build-up when water is suddenly shut off at the power station.
The construction of dams, power stations and water channels is co-ordinated so the different parts are completed together and ready to produce electricity at the earliest possible time.
Penstocks at Tarraleah
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