HYDRO POWER PLANT
BASIC TERMS, TYPES and
Faculty in Mechanical Engineering
TYPES OF POWER HOUSE
• Semi Under Ground
• Under Ground.
SURFACE POWER HOUSE
• All components of the Hydro power projects are
on the natural/excavated ground surface.
Surface power house has the advantage of pre-determined
topography ,design and is easy to
construct. However, these have the
disadvantage of limitation of head available as
per the topography.
• In such projects the water inlet to the machines
could be from a penstock or from a tunnel
terminating into a penstock. The water outlet
goes into a tail race.
• If the power house is located just adjacent to the
Dam then it is sometimes called a Dam-toe
Surface power house
Semi Underground powerhouse
Some components of the power house are
underground, while others are on surface.
The advantages of both surface &
underground are clubbed together in a
semi-underground powerhouse, provided
topography & geology so permit.
UNDER GROUND POWER HOUSE
• Depending on the topography, a power house may
have to be located inside a mountain. Such a
power house is called an under ground power
• In such power houses the complete power house
equipment are located inside Cavern. In such
power houses various tunnels such as Head race
tunnel for the water inflow to the turbine, Tail race
tunnel for water out flow of the turbine and various
access tunnel have to be provided inside the
• Such power houses take greater amount of time
and capital cost to construct.
• This is very advantages as it overcomes
the limitations of head available as per
topography and provide compact and
• This requires less land and consequently
reduce rehabilitation and resettlement
problems(R&R). However, this has the
disadvantages of geological uncertainties
resulting into indeterminate design and
construction problems leading to time and
cost over runs
Salient Features of Uri Project
(underground power house)
Under ground power house of – 4 X 120MW.
HRT - 10.6 km X 9.5m dia. Horse shoe Concrete lined
TRT - 2.2 km X 9.5m dia Horse shoe Concrete lined
Surge Shaft - 22m circular X 90m depth
Adits- 4Nos Total1.7km X 6m modified shoe
Adits- 6-TRT .471km X 6.5 X 7m modified shoe
Main Access -- .630km tunnel
Total Tunneling- 19.34km
Machine Hall- 127mLx22mBx28mH
All the equipment are placed inside a Cavern
Underground Chamera HEP
TYPE OF HYDRO POWER
• Multi-purpose Project
• Purely Hydro-electric Project
• Run of river project
• Storage Project
• Pump Storage project
Power generation may be one of the
benefits along with Flood Control,
Irrigation, Navigation, Drinking Water
Purely Hydro-electric Project
Project is conceived exclusively for
Run of River Project
• As the name implies, the project is planned as run of
• Water is diverted from the river, routed through the
water conductor system and finally water after
generation of power is thrown back to the river at a
lower level on down stream.
• It takes advantage of the drop in elevation that
occurs over a distance in the river and does not
involve water storage.
• Power generation fluctuates with the river flow and
the firm power is considerably low, as it depends on
the minimum mean discharge.
• Canal power projects are also run-of-river projects.
• Storage projects provide storage or
pondage and thereby, evens out stream
flow fluctuations and enhances the water
• It increases firm power and total power
generation by regulating the flow.
• Providing storage is complicated and
costly as it involves construction of dam.
Pump Storage project
• Pump storage projects involve reversible turbines,
which can generate power from water of upper
reservoir during peak hours and pump back water from
lower reservoir to the upper reservoir during off peak
• These projects are advantageous in power system of
mix type, which have thermal and nuclear power
houses in addition to hydro power projects.
• Pump storage project utilizes the off peak surplus
power of the grid in lifting the water from lower
reservoir to higher reservoir and generates power
during peak hours thus flattening the load curve.
HYDRO DEVELOPMENT- IMPORTANT
• FRL (FULL RESERVOIR LEVEL)
FRL is the Upper level of the reservoir (selected based
on techno-economic& submergence considerations)
• MDDL (MINIMUM DRAWDOWN LEVEL)
Lowest level up to which the reservoir level could be
drawn down to withdraw waters for energy generation
(selected from considerations of silt & turbine
• GROSS STORAGE
Total storage capacity of the reservoir
Hydro Development- IMPORTANT TERMS-Cont
• DEAD STORAGE
Reservoir storage which cannot be used for generation
and is left for silt deposition( below MDDL)
• LIVE STORAGE
The storage in the reservoir which is available for power
generation (between FRL & MDDL)
• FIRM POWER
Continuous power output in the entire period of
hydrological data at 90% dependability
• FIRM ENERGY
Energy generated corresponding to firm power
Hydro Development- IMPORTANT
• Peak Energy
Electric energy supplied during periods of relatively high
• Off-peak Energy
Electric energy supplied during periods of relatively low
• Load Factor
Ratio of the average load over a designated period to the
peak-load occurring in that period
• DIURNAL STORAGE
Storage required to meet daily variations in load demand. It
depends upon the minimum flows and peak discharges.
Hydro Development- IMPORTANT TERMS
• CRITICAL PERIOD
Most critical period with respect to system load
requirements, begins when reservoir begins
delivering water for generation from full i.e the
available storage is fully drafted at one point
during the period; and the critical period ends
when the storage has completely refilled.
• CRITICAL DRAW DOWN PERIOD
That portion of the critical period in which
reservoir live storage is completely drafted while
meeting firm energy requirements
IMPORTANT TERMS HEAD – Cont.
• Design Head
The head at which the turbine will operate
to give the best overall efficiency
under various operating conditions.
• Gross Head
The difference of elevations between
water surfaces of the forebay/ dam and
tailrace under specified conditions.
• Net Head
The gross head chargeable to the turbine
less all hydraulic losses in water
Major components of Hydro
• Water Conductor System
• Power House
• Located on rivers, where rock is
available at larger depth.
• The dam/ Barrage is used for
delivering/diverting the water to
the water conductor system.
• The barrage is used to regulate the
water for power generation.
Water Conductor System
• Water conductor system consists of
head race tunnel of suitable size.
• Water conductor system may consist
of tunnel, channel, cut and cover as
per the topography involved.
• At end of tunnel there is surge shaft.
• The water conductor system conveys
water to penstock.
Components of Water
• Water intake structure
• Head Race Tunnel
• Surge shaft ,Pressure shaft ,gates,
gates and hoisting mechanism
• Penstock Protection Valve
• Main inlet Valve
• Tail Race Tunnel
Water Intake Structure
• It consists of gated structure at the
dam/Barrage to control the flow of
water and provided with gates along
with hoisting arrangement.
• Normally these gates remain open and
allows water to flow to the tunnel
/channel as the case may be until and
unless water conductor system is
taken under shut down for repair and
• Surge shaft is located at the end of
• It is a well type structure of suitable
height and diameter to absorb the
upcoming and lowering surges in case
of tripping and starting of the machine
in the power house.
• The surge shaft is provided with gates
to stop flow of water to the penstock if
repairs are to be carried out in the
penstock or inlet valves.
Penstock Protection Valve
The Penstock protection valves are
provided after the surge shaft to facilitate
maintenance of the penstocks. The valves
are of butterfly type. The BF valve are
operated hydraulically with provision of
pressure accumulators in case of power
• When the water conduits in the Surge
shaft and Main Inlet valve are not exposed
to the atmosphere and buried in the
ground/concrete due to its high pressure,
these are called Pressure shaft.
• Penstocks are the water conductor conduit of
suitable size connecting the surge shaft to main
• It allows water to the turbine through main inlet
• At the end of the penstock a drainage valve is
provided which drains water from penstock to
the draft tube.
• In case of long penstock and high head,
butterfly valve is provided just before the
• It takes off from the surge shaft in addition to
spherical valve at the end of the penstock acting
as the main inlet valve.
Main Inlet Valve
• Main inlet valve works as the gate
valve/isolating valve in the water
• It is located before turbine and allows
water flow from penstock to turbine.
• MIV acts as closing valve and cuts the
flow of water during an emergency trip.
• They are of following type.
• Butterfly valve (upto 200 m head)
• Spherical valve (more than200m head)
Components of MIV
• Spherical valve/Butterfly valve
• Bypass valve
• Oil pumping unit
Spherical valve consist of plate which is in line with
the flow of water when in open condition and in
totally vertical direction when in closed position.
Bypass valve acts as a means to charge the
spherical valve and balance the pressure on either
side of valve I,e penstock and turbine
Oil pumping unit is used to pump the oil to operate
• Draft tube is located between lower ring of
turbine and tail race . It conveys water after
discharge from runner to tail race tunnel.
• Draft tube (DT) gates are provided for
isolating the Power house and tail pool
before taking maintenance of the turbine.
• The DT gates are provided with hoisting
• The DT gate may be a single piece or a
combination of more than one piece
• The hydro project are site specific as such
the use of standard or off the shelf unit may
not be possible. The selection of type of
turbine is made on the basis of “Head”. The
broad classification is given below.
• Low head(upto60 m)– Kaplan Turbine
• Medium head(30to600m)—Francis Turbine
• High head (more than300m) Pelton
• The hydraulic turbine governor
is equipment for controlling the
guide vanes by detecting turbine
speed and its guide vane
opening in order to keep the
turbine speed stable or to
regulate it's output
• Governors are provided with the
Quick Response and Stable
Guide Vane Opening Detection
with High Accuracy
Speed Detection with High
1.What are the component of water
Ans:Intake structure, Head race tunnel,
Surge shaft,Penestock, MIV,Draft tube
and Tail RaceTunnel
MDDL-Minimum draw down level(yes/no)
3.FRL- Full reservoir level (yes/no)
4.RUN OF RIVER have pondage (yes/no)
5. Pumped storage scheme are generally
used for peaking power (yes/no)
6.Dewatering system is used to dewater the
draft tube and other turbine component
7. Surge Shaft is used control upsurge/lower
Surge in the hydro power station (yes/no)
8.Under ground power station is installed w
here there is scarcity of land(yes/no)
9.GIS stands for Gas insulated Switchgear
10.What are advantages of GIS over
• What are the main component on turbine?
• Why single phase transformers are
preferred in hydro power plant?
• Sulfer Hexafluoride gas(SF6) is used in GIS.
• Rotor is the heaviest part of hydro
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