HYDROLOGY AND WATER RESOURCE MANAGMENT

PRINCIPLE COMPONENTS OF HYDROELECTRIC POWER PLANT

ALAY MEHTA 141080106011 SHIVANI PATEL 141080106021 KAVIN RAVAL 141080106026 KUNTAL SONI 141080106028

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INTRODUCTION COMPONENTS PRINCIPLE SCHEME

PRINCIPAL COMPONENT OF HYDROELECTRIC SCHEMEThe principal components of a hydroelectric scheme are as under:

1. Intake structure2. Forebay3. Surge tank4. Penstocks5. Conveyance systems6. Power house7. Draft tube8. Tail race

1. INTAKE STRUCTUREAn intake is a structure constructed at the entrance of the pipe or canal or tunnel through which water is conveyed to the power house.The intake serves the following functions:

i. It controls the flow of water into the conveyance system.

ii. It prevents the entry of debris, ice, boulders, etc. into the conveyance systems by means trash racks.

iii. It prevents the heavy sediment load of the river from entering the conveyance system with help of silt traps and silt excluders.

iv. It provides a smooth, easy and turbulence free entry of water into the conveyance system.

TYPES OF INTAKEThe type of intake most suitable for a particular project will depend upon the type of storage or diversion structure, the location of the power house, the conveyance system, topography, etc.

Commonly used intakes are:1. Dam intake2. Run-of-river intake3. Canal intake4. Tower intake5. Shaft intake

Intake Structure

2. FOREBAY• A forebay is an enlarged body of water provided at the

downstream end of the canal just at the upstream of penstocks to act as a small balancing reservoir or pond.

• The main function of the forebay is to store some water to act as a regulating reservoir for the penstocks.

• The forebay should be provide with an outlet or spill way to dispose of the water safety whenever required.

• A forebay is usually created by widening the downstream and of the power canal into the form of a small basin.

• Sometimes a byepass is provided to convey water from the forebay to the tailrace when the load is reduced.

Fore bay

3. SURGE TANKIf the conveyance system consists of a penstock under a very high pressure, a surge tank is usually required at the upstream of the powerhouse to reduce the water hammer effect.Functions of surge tank:1. It provides a free reservoir surface just upstream

of the turbine intake to absorb and compensate water hammer effects.

2. It reduces the length of the high pressure conduits required to resist the water hammer effects.

3. It quickly dampens the water level fluctuations following load changes.

Types of surge tanks:Basically surge tanks are of three types:

1. Simple surge tank 2. Restricted entry surge tank3. Differential surge tank

Surge Tank

4. penstocks• Penstocks are the pressure pipes which convey water

from the intake to the turbines.• If the power house is located at the toe of the dam,

penstocks are entirely embedded in the dam.• When power house is located away from the dam,

penstocks are provided to take the water from the dam to the power house.

• Sometimes, a canal is provided in initial reach ending in a forebay and the penstocks are provided in the remaining reach.

• When the distance between the forebay and the power house is relarively short, a separate penstock is provided for each turbine.

Penstocks

5. CONVEYANCE SYSTEMSA conveyance system is required to carry the water from the intake to the power house. It may consist of one of the followings:1. Canals 2. Closed conduits3. Tunnels 4. Penstocks• When the general topography of the terrain is

moderate and the discharge is large, canals are generally most suitable.

• The tunnel may have pressure flow or free flow. When the ground is very steep and rugged, penstocks are more economical.

• In the case of an open channel, a forebay is usually provided at the end of the channel from which the water is conveyed to the turbines through penstocks.

Conveyance System

6. POWER HOUSE

A power house is a building constructed for housing and protection of the various hydraulic and electrical equipments required for the generation of power, such as spiral casing, turbines, governors, draft tube, generators, etc.

The power house consists of three main components:

1. Substructure2. Intermediate structure3. Superstructure

Power House

7. DRAFT TUBEA draft tube is a pipe or passage of gradually increasing cross-sectional area which connects the runner exit to the tail race.It serves the following purposes:1. It permits a negative or suction head to be

established at the runner exit, thus making it possible the placing of wheel and connecting machinery at level above that of water in the tail race under high-water flow conditions of river, without loss of head.

2. It reduces the high velocity of the water discharged by the turbine by gradually enlarging the cross-section and thus converts the kinetic energy of the water leaving the runner, into mechanical energy of the wheel. Thus it acts as a recuperator of pressure energy.

Draft Tube

8. TAIL RACE• The tail race is the channel into which the water is

discharged after passing through the turbines, if the power house is close to the stream, the outflow may be discharged directly into the stream.

• On the other hand, if the power house is located away from the stream, the tail race is formed by constructing an artificial channel between the power house and the stream.

• A draft tube of a reaction turbine discharged at a level below the river bed. The upslope of the tail race is usually kept 1 in 6, from the draft tube exit to the river bed.

• For pelton wheels, a small rectangular or trapezoidal tail race is provided because the discharged is relatively small.

Tail Race

PRINCIPAL COMPONENTS OF HYDROELECTRIC SCHEME