A trash rack is a wooden or metal structure, that prevents waterborne debris (such as logs, boats, animals, masses of cut
waterweed, etc.) from entering the intake of channel. This protects
water penstock, and sluice gates from destruction.
Trash racks composed of vertical wooden strakes separated by
narrow gaps are very common and perform extremely poorly. Metal
gratings are sturdier and can have narrower strakes, and angling the
trash rack properly can allow some self-cleaning from the action of the
Modern trash racks as used by hydroelectric plants can incorporate
advanced feature as cleaning robots for their cleaning purposes.
Trash racks are designed for water velocity of around 2 feet/second
(0.6 metres/second) to prevent excessive energy loss due to the head
loss across the trash rack. Close spacing keeps out more small floating
debris or fish
It is an structure constructed in such a manner so
as to direct water to the intake channel.
The advantages of diversion structures include the following:
• Reduces the volume of flow across disturbed areas, thereby
reducing the potential for erosion.
• Breaks up the concentration of water on long slopes
• Allows sediment basins and traps to function efficiently by
maintaining a separation
between clean water and sediment-laden water
• Easily constructed with equipment found on most
The limitations of diversion structures include the following:
• High flow velocities can cause erosion in the diversion
• Diversion structures must be stabilized immediately after
It is the channel to which water is diverted by the diversion weir and fed into
the desilting tank.The purpose of creating intake channel is:
Assured water supply
Suitable quality of water
Control over supply of water
Safety against flood
It is the tank from which silt is excluded from the water which has
entered into the intake channel. There are two types of de-silting
Preventive : The entry of sediment checked
before its entry into the head regulation.
These are constructed in the streams.
Curative : The sediment is excluded from the
channel after its entry with the channel.
These are constructed in the channel.
It is the channel through which water is being carried to the forebay tank
for feeding to penstock. The various types of power channels are listed
• Reinforced concrete pipe
• PVC pipes
• Steel pipes
It is a reservoir, basin or tank located just before the entrance
to the penstock.
The purpose of the forebay is:
To provide immediate water demand on starting the
It can serve as a final settling basin
The forebay provides some storage in case of sudden
failure of the system
To spill the extra water
Forebay components include:Basin, Spillway,Gate or
Valve,Outlet,Trashrack, Air Vent,1 to 2% of penstock
A penstock is an enclosed pipe that delivers water to hydraulic
turbines for the power generation purpose. Hydraulic Turbines act as a
prime mover for the generator shaft due to which we get electrical
power. Penstocks for hydroelectric installations are normally equipped
with a gate system and a surge tank. Flow is regulated by turbine
operation and is nil when turbines are not in service. The materials
used for penstock construction are:
Reinforced Concrete Pipe
Glass fibre reinforced plastic pipe
Glass fibre reinforced concrete
The inlet valve in a Hydro Power station is used as a safety
The inlet valve is used for regulating flow of water into the
It is also used for isolating the Hydro-turbine for
Hydro turbines are needed for the conversion of hydro energy to mechanical
energy.The various types of turbines are shown below:
ONLY K.E IS UTILISED
K.E AND PRESSURE ENERGY
NOZZLE FOR DISCHARGE
GUIDE VANES FOR
An induction generator or asynchronous generator is a type of AC
electrical generator that uses the principles of induction motors to
produce power. Induction generators operate by mechanically turning
their rotor faster than the synchronous speed, giving negative slip. A
regular AC asynchronous motor usually can be used as a
generator, without any internal modifications. Induction generators are
useful in applications such as hydro- power plants, wind turbines etc.
It has following featuresLOW COST
SINGLY EXCITED MACHINE
ABSORBER OF REACTIVE POWER FROM THE SYSTEM
SPEED Vs TORQUE CHARACTERISTICS
OF AN INDUCTION MACHINE
A synchronous generator is an electrical machine producing alternating emf
(Electtromotive force or voltage) of constant frequency. In our country the standard
commercial frequency of AC supply is 50 Hz. In U.S.A. and a few other countries
the frequency is 60 Hz. These are of two types-Cylindrical or Round rotor type
and Salient Pole type but in Hydropower applications Salient Pole synchronous
alternators are used.They have the following features:
REACTIVE POWER CAN BE SUPPLIED OR ABSORBED
In an electric power system, switchgear is the combination of electrical disconnect
switches, fuses or circuit breakers used to control, protect and isolate electrical
equipment. Switchgear is used both to de-energize equipment to allow work to be
done and to clear faults downstream. This type of equipment is important because
it is directly linked to the reliability of the electricity supply.
RELAY AND CB OPERATION
Karassik, Igor J. et al, eds.; Pump Handbook (3rd Edition), McGraw-Hill 2001
ISBN 978-0-07-034032-9 page 10-5
U.S. Army Corps of Engineers, Ice Engineering - Engineering and Design (EM
1110-2-1612) ISBN 978-1-61583-638-3 page 20-11
Fluid Mechanics: Fundamentals and Applications, 2/e
Yunus A Çengel, University of Nevada, Reno
John M Cimbala, Pennsylvania State University
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