Hydropower generation with block diagram

A hydropower plant converts the potential energy of water stored at a height into kinetic energy, then into mechanical energy in a turbine, and finally into electrical energy in a generator. Power available:

$$P = \eta\rho g Q H\quad(\text{W})$$

where $Q$ = discharge (m³/s), $H$ = net head (m), $\eta$ = overall efficiency.

Block diagram

 [Reservoir/Intake/Dam]
          |
   [Headrace / tunnel]
          |
 [Forebay / surge tank]
          |
      [Penstock]
          |
   [Turbine] --shaft--> [Generator] -> [Step-up Tx]
          |                 |              |
     [Tailrace]       [Exciter, AVR]   [Switchyard]
          |                                |
        River                           Grid

Working

1. Dam/intake: Stores or diverts river water and creates head.
2. Headrace and forebay/surge tank: Carry water to the penstock; the surge tank absorbs pressure changes (water hammer).
3. Penstock: Pressure pipe that brings water down to the powerhouse, converting potential energy to pressure/kinetic energy.
4. Turbine: Pelton (high head), Francis (medium head) or Kaplan (low head) turns the water energy into shaft rotation; governor controls flow to keep speed constant.
5. Generator: Synchronous generator coupled to the turbine produces 3-phase AC at 11 kV.
6. Transformer and switchyard: Step up the voltage (e.g. 11/132 kV) and connect to the grid.
7. Tailrace: Returns water to the river.

Example: Kali Gandaki "A" (144 MW) in Nepal uses this arrangement with Francis turbines.