The highest dam worldwide is currently Jinping-I, a 305 m high concrete arch-shaped dam in China on the river Yalong.

Francis turbines are currently the most common water turbine and can achieve over 95% efficiency. They can be used for hydraulic heads between 20 and 700 meters. It is very often installed in pumped-storage hydroelectric power plants

In times of electricity overproduction, this plant consumes electricity and pumps water from the lower reservoir up to the upper one. When the load peaks, when there is not enough energy in the grid, the accumulated water is released to drive turbines and power generators and returns the accumulated energy back to the grid.

Electrical generators located above the water turbines generate current that is conducted to an external substation where its voltage is transformed to match the transmission system. The hydropower plant's output is then supplied to the transmission network, usually through above-ground lines.

The most important part of the hydropower plant is the building containing all the power generating equipment. It is usually located below the dam, at the same level as the bottom reservoir or watercourse. It has a separate floor for water turbines, a floor with electrical generators, and other areas used to control, maintain, and operate the hydropower plant.

The rock at the bottom of the river valley. The structure and the properties of this rock are determining factors for the choice of the type of dam to be built.

A structural feature in the dam wall that allows safe spilling of surplus water that may otherwise flow over the edge of the dam.

A reservoir enclosed by the dam and the slopes of the river valley. It can hold an enormous volume of water. The level of water in the reservoir and the rate of flow at the dam are controllable.

A barrier built across a stream of water so as to dam it, increasing the hydraulic head, and storing the water needed for running the turbines. The biggest dams, holding the most water, are built for accumulation for hydroelectric power plants. Dams can be categorized as gravitational if the sheer weight of the dam retains the water. Other types are concrete arch dams or pillar-supported dams.

The highest dam worldwide is currently Jinping-I with 305 m high concreate arch-shaped dam in China on river Yalong.

In the case of a pumped-storage power plant, the bottom reservoir is used when the plant is in turbine mode to capture water after it has passed through the turbines. In pumping mode, the reversible turbines transport the water back to the upper reservoir.

A tube situated at the bottom of a turbine, which helps increase its output by creating negative pressure at the water outlet of the runner.

A channel leading pressurized water from the reservoir to the turbines of the hydroelectric power plant.

An electric device for increasing the voltage of the electricity produced to the voltage of the power grid so as to minimize loss during transmission.

A reservoir enclosed by the dam and the slopes of the river valley. It can hold an enormous volume of water. The level of water in the reservoir and the rate of flow at the dam are controllable.

A structure that directs water from the reservoir into the penstock. It incorporates screens and gates, which can stop the water flow to the turbines.

A barrier built across a stream of water so as to dam it, increasing the hydraulic head, and storing the water needed for running the turbines. The biggest dams, holding the most water, are built for accumulation for hydroelectric power plants. Dams can be categorized as gravitational if the sheer weight of the dam retains the water. Other types are concrete arch dams or pillar-supported dams.

A device for transforming the mechanical energy of the turning rotor into electric energy through electromagnetic induction. Due to the lower rotation frequency of water turbines, generators in hydroelectric power plants are much larger than generators of the same output in thermal power plants.

A reaction water turbine with variable pitch for both the guide vanes (or wicket gates), and the runner blades. It is suitable for hydraulic heads between 5 and 80 meters and rates of flow up to several hundreds of m³/s. The rotation frequency can be precisely adjusted, which is why these turbines are used in places with variable rates of flow.

The runner is usually fitted with three to twelve adjustable blades and is reminiscent of a ship propeller. To accommodate to actual rates of flow, the pitch of the runner blades is changed using a mechanism fitted inside the hollow axis of the runner.

Spiral casings are used at the turbine inlet to uniformly distribute the water around the circumference of the guide vanes. As it passes through the channels between the guides, the water is uniformly directed along the entire circumference at the rotor of the Kaplan turbine.

A hydraulic system is used to simply adjust the position of all guide vanes at once. Lever mechanisms on the guide vanes are connected to a central control ring, which is usually turned by several hydraulic push–pull rods.

Water is led to a turbine via the penstock and through the guide vanes, where it gains speed and alters direction. Guide vanes (also called wicket gates) are adjustable and their position determines the flow rate and velocity of the water passing through the turbine. They are situated around the runner and when fully open the turbine operates at maximum power.

The shaft is connected to the shaft of the generator. The mechanical energy of the rotating shaft is converted in an electric generator into a rotation of the rotor and finally converted into electric power.

A device for transforming the mechanical energy of the turning rotor into electric energy through electromagnetic induction. Due to the lower rotation frequency of water turbines, generators in hydroelectric power plants are much larger than generators of the same output in thermal power plants.

A tube situated at the bottom of a turbine, which helps increase its output by creating negative pressure at the water outlet of the runner. It leads the water to the lower reservoir.

The father of the term 'turbine' is the French engineer Claude Bourdin. It was the name for his rotating water engine (in Latin: turbo = rotate) which he constructed in 1826.

In an electrical generator the stator transforms the rotating magnetic field into electrical current. This is accomplished by stator coils situated in the steel core around the rotor. In hydropower generators, large-diameter multi-pole stators are used, usually installed above the water turbine.

Current in the rotating rotor windings creates a rotating magnetic field, which induces voltage in the stator coils. The rotors of generators in hydropower plants are run at low speed and have a larger number of poles. Due to the lower rotation frequency of water turbines, rotors in hydroelectric power plants are much larger than generators of the same output in thermal power plants.

The output of the Kaplan turbine ranges from 5 to 200 MW.

The shaft is connected to the shaft of the generator. The mechanical energy of the rotating shaft is converted in an electric generator into a rotation of the rotor and finally converted into electric power.

A reaction water turbine with variable pitch for both the guide vanes (or wicket gates), and the runner blades. It is suitable for hydraulic heads between 5 and 80 meters and rates of flow up to several hundreds of m³/s. The rotation frequency can be precisely adjusted, which is why these turbines are used in places with variable rates of flow.

A channel leading pressurized water from the reservoir to the turbines of the hydroelectric power plant.

Spiral casings are used at the turbine inlet to uniformly distribute the water around the circumference of the guide vanes. As it passes through the channels between the guides, the water is uniformly directed along the entire circumference at the rotor of the Francis turbine.

Guide vanes regulate the rate of flow. The guide vanes are controlled by a centralized system that allows simultaneous setting change for all vanes.

The shaft is connected to the shaft of the generator. The mechanical energy of the rotating shaft is converted in an electric generator into a rotation of the rotor and finally converted into electric power.

A tube situated at the bottom of a turbine, which helps increase its output by creating negative pressure at the water outlet of the runner.

The biggest Francis turbines were made for the Three Gorges hydroelectric power plant in China. The runners have a diameter of 10 m and an output capacity of up to 760 MW.

A surge tank is a cylinder with an open surface connected to the upper part of pressure feeders at a pumped-storage power plant. Its purpose is to accommodate hydraulic surges that occur when water is being handled in pressure feeders.

A penstock is a pipe connecting the upper reservoir to the power house containing the turbines. It is usually pressure-resistant steel piping installed on the surface or underground in special channels. In pumped-storage power plants, it is used to conduct water to the turbines as well as to pump water back to the top reservoir.

This is an artificially created chamber where valves are installed on the penstock. If it needs to be inspected, repaired, or the power plant needs to be shut down, each penstock can be shut off separately.

In times of electricity overproduction, this plant consumes electricity and pumps water from the lower reservoir up to the upper one. When the load peaks, when there is not enough energy in the grid, the accumulated water is released to drive turbines and power generators and returns the accumulated energy back to the grid. To produce 1 kW of electricity, a pumped storage plant consumes roughly 1,3 kW during the off-peak time. A significant advantage of pumped-storage power plants is their capacity to quickly change their mode of operation from pumping to power generation within just a few minutes and, in this way, to respond to the actual load situation in the grid dynamically.

This structure is located where the penstocks connect to the upper reservoir. Its primary purpose is to prevent debris that could damage the turbine from entering the penstocks.

The upper reservoir of a pumped-storage hydropower plant stores energy in the form of potential energy of water that is repeatedly pumped into the upper reservoir when electricity is cheaper and used to generate electricity during peak periods. The reservoir must be well-sealed and can but need not have natural tributaries.