Hydroelectric power plant

Hydroelectric power plant: Points : Hydroelectric power plant, Storage reservoir, Dam and its parts, Water ways, Water turbines and electric generators, Impulse turbines It consists of the following main components:
1. Storage reservoir,
2. Dam and its parts,
3. Water ways,
4. Water turbines and electric generators.
5. Impulse turbines: 1. Storage Reservoir: The water available from the catchment area is stored in the reservoir. The capacity of reservoir should be such that the water should be available for running the turbines, for producing the desired quantity of electric power, throughout the year. A reservoir may be natural or artificial. 2. Dams and its Parts: A dam is constructed across a river in order to check the flow of water and impound it in the reservoir formed on the upstream side. The size and type of dam depends upon the character of river, head of water, amount of discharge etc. Its shape and other components are decided by tests on model in the laboratory.
The dam are provided with gates for regulating the flow of water. There is also an arrangement for automatic overflow of excess water. Some means are also provide for removing slit from the reservoir just closer to the dam. It is still a problem, which the engineers working on the maintenance of dams, have not, been able to solve successfully. 3. Water Ways: A waterway is a passage through which the water is carried from the dam to the power house and then to the river. The upstream position is known as head race and the downstream as tail race. It may consist of tunnels canals, flumes, pipes or any other suitable arrangement. A surge tank is also provided just on the upstream of the power house to control the pressure variation and eliminate the effects of water hammer. 4. Water turbines and electric generators: A place, where water turbines and electric generators are installed, is called power house. its design is very complicated and requires lot of skill. In this book, we shall discuss the design of water turbines only, as the design of electric generator is beyond the scope of this book.

The position of a power house is decided by considering factors such as space available, transport facilities etc. The size of a power house is decided by considering the factors such as supply height, number and size of units, type of units electrical arrangements etc. The electrical generators are directly coupled with the turbines for better efficiency.

The turbines may be designed and laid either with their shafts horizontal or vertical, in a horizontal shaft lay out, the whole-installation lies on the same floor. Thus it is very easy to carry out inspection, service or any other modification in the plant. In a vertical shaft lay out, it is convenient to connect incoming pipe and outgoing draft tube. Moreover, the generators are spaced well above the water surface, which makes their inspection, service and maintenance easier. 5. Impulse turbines: An impulse turbine, as the name indicates, is a turbine which runs by the impulse of water. In an impulse turbine, the water from a dam is made to flow through a pipeline, and then through guide mechanism and finally through the nozzle. In such a process, the entire available energy of the water is converted into kinetic energy, by passing it through nozzles; which are kept close to the runner. The water enters the running wheel in the form of a jet (or jets), which impinges on the buckets, fixed to the outer periphery of the wheel. The jet of water impinges on the buckets with a high velocity, and after flowing over the vanes, leaves with a low velocity; thus imparting energy to the runner. The pressure of water, both at entering and leaving the vanes, is atmospheric. The commonest example of an impulsive is Pelton wheel, which is discussed below.