Hydro Electric Power Plant
ELEMENTS OF HYDRO-ELECTRIC POWER PLANT
A hydro-electric plant consists of a reservoir for storage of water, a diversion dam, an intake structure for controlling and regulating the flow of water, a conduit system to carry the water from the intake to the water wheel, the turbines coupled with generators, the draft tube for conveying water from water wheel to the tailrace, the tailrace and a powerhouse 1.e. the building to contain the turbines, generators, the accessories and other miscellaneous items. The size, location, and type of each of these essential elements depend upon the topography and geological conditions and the amount of water to be used.
The height to which the dam may be built is usually limited by the extent of flowage damage. Pondage can also have a remarkable value, in particular for peak load energy plants, warranting the purchase of widespread flowage rights. The spillway section of the dam must be long enough to pass safely the maximum amount of water to be expected. Likewise, the abutments and other short structures must be built to withstand successfully the greatest freshet conceivable on the river
The components of the Hydro Power house.
✓✓ Flowing streams
✓✓ Water head
✓✓ Water holding capacity
✓✓ Water pressure
✓✓ Catchment area
✓✓ Reservoir (water storage)
✓✓ Surge tank
Hydroelectric power plant equipment
✓✓ Water turban
✓✓ Gate valve
✓✓ Relief Valve
✓✓ Flow measurement equipment
✓✓ Water circulating pump
✓✓ water circuit breaker
✓✓ Switch board equipment
✓✓ Low and high tension busbar
✓✓ Storage batteries
✓✓ Outgoing connection
✓✓ Shops and offices
It is the basic requirement of a hydro-electric plant. Its purpose is to store water during excess flow periods (i.e. rainy season) and supply the same during lean flow periods (i.e. dry season) and thus it helps in supplying water to the turbines according to the load on the power plant. A reservoir can be either natural or artificial. A herbal reservoir is a lake in high mountains and an artificial reservoir is made by constructing a dam throughout the river. Low head plants require a very large storage reservoir. The capacity of the reservoir depends on the difference between run-offs during high and lean flows.
The function of a dam is not only to raise the water surface of the stream to create an artificial head but also to provide the pondage, storage or the facility of diversion into conduits. A dam is the most expensive and important part of a hydro-project. Dams are built of concrete or stone masonary, earth or rock fill earth or rock fill. The type and arrangement depending upon the topography of the site. A masonary dam may be built in a narrow canyon. An earth dam may be best suited for a wide valley. The choice of the dam also depends upon the foundation conditions, local materials, and transportation available, the occurrence of earthquakes and other hazards.
Mansory dams are of three major classes viz solid gravity, buttress, and the arch dams.
Sold gravity dam shown in fig. 2.6 (a), is made of concrete and is suitable for most sites. The height of the dam, which cannot be very high, depends on the Arch dam, shown in fig. 2.6 (b) is a curved dam and transmits a major portion of its water pressure horizontally to the abutments by arch action. An arch dam is preferred where a narrow canyon width is available. This dam has inherent stability against sliding.
The buttress or deck dam has an inclined upstream face, so that water pressure creates a massive downward force that presents balance against overturning or sliding. Such a dam is more suitable for weak foundations and earthquake-prone sites. An earth dam has a very wide base as compared to its height. Such dams are quite suitable for a pervious foundation because the wide base provides a long seepage path. The earth dams have got the following advantages.