Electrical B.Tech UET Peshawar solved papers

1. 1
Sources of Energy: The followings are the various sources of energy:
1) The Sun (2) The Wind (3) Water (4) Fuels (5) Nuclear
Energy
1. The Sun: The Sun is the primary source of energy. The heat energy
radiated by the Sun can be focused over a small area by means of reflectors.
This heat can be used to raise steam and electrical energy can be produced
with the help of turbine-alternator combination. However, this method has
limited application because:
(a) It requires a large area for the generation of even a small amount of
electric power
(b) It cannot be used in cloudy days or at night
(c) It is an uneconomical method.
Nevertheless, there are some locations in the world where strong
solar radiation is received very regularly and the sources of mineral
fuel are scanty or lacking. Such locations offer more interest to the
solar plant builders.
(ii) The Wind: This method can be used where wind flows for a
considerable length of time. The wind energy is used to run the wind
mill which drives a small generator. In order to obtain the electrical
energy from a wind mill continuously, the generator is arranged to
charge the batteries. These batteries supply the energy when the
wind stops. This method has the advantages that maintenance
and generation costs are negligible. However, the drawbacks of
this method are (a) variable output, (b) unreliable because of
uncertainty about wind pressure and (c) power generated is quite
small.
(iii) Water: When water is stored at a suitable place, it possesses
potential energy because of the head created. This water energy can
be converted into mechanical energy with the help of water turbines.
The water turbine drives the alternator which converts mechanical
energy into electrical energy. This method of generation of electrical
energy has become very popular because it has low production and
maintenance costs.

2. 2
(iv) Fuels: The main sources of energy are fuels viz., solid fuel as
coal, liquid fuel as oil and gas fuel as natural gas. The heat energy of
these fuels is converted into mechanical energy by suitable prime
movers such as steam engines, steam turbines, internal combustion
engines etc. The prime mover drives the alternator which converts
mechanical energy into electrical energy. Although fuels continue to
enjoy the place of chief source for the generation of electrical energy,
yet their reserves are diminishing day by day. Therefore, the present
trend is to harness water power which is more or less a permanent
source of power.
(v) Nuclear energy: Towards the end of Second World War, it was
discovered that large amount of heat energy is liberated by the fission
of uranium and other fissionable materials. It is estimated that heat
produced by 1 kg of nuclear fuel is equal to that produced by 4500
tonnes of coal. The heat produced due to nuclear fission can be
utilized to raise steam with suitable arrangements. The steam can run
the steam turbine which in turn can drive the alternator to produce
electrical energy. However, there are some difficulties in the use of
nuclear energy. The principal ones are (a) high cost of nuclear plant
(b) problem of disposal of radioactive waste and dearth of trained
personnel to handle the plant.

3. 3
Reason for present energy crisis all around the world:
The followings are main reasons for present energy crisis all around the world.
1. Overconsumption: The energy crisis is a result of many different strains
on our natural resources, not just one.
2. Overpopulation: Another cause of the crisis has been the steady increase
in the world’s population and its demands for fuel and products.
3. Poor Infrastructure: Most of the energy producing firms keeps on using
outdated equipment that restricts the production of energy.
4. Unexplored Renewable Energy Options: Renewable energy still remains
unused are most of the countries.
5. Delay in Commissioning of Power Plants: In few countries, there is a
significant delay in commissioning of new power plants that can fill the gap
between demand and supply of energy. The result is that old plants come
under huge stress to meet the daily demand for power. When supply don’t
matches demand, hence results in load shedding and breakdown.
6. Wastage of Energy: In most parts of the world, people do not realize the
importance of conserving energy.
7. Poor Distribution System: Frequent tripping and breakdown are result of
a poor distribution system.
8. Major Accidents and Natural Calamities: Major accidents like pipeline
burst and natural calamities like eruption of volcanoes, floods, earthquakes
can also cause interruptions to energy supplies.

4. 4
Types of Dams used in Hydro-electric power station:
Based on the functions of dams:
Storage dams: They are constructed to store water during the rainy season
when there is a large flow in the river.
Diversion dams: A diversion dam is constructed for the purpose of diverting
water of the river into an off-taking canal (or a conduit). They provide sufficient
pressure for pushing water into ditches, canals, or other conveyance systems.
Detention dams: Detention dams are constructed for flood control. A detention
dam retards the flow in the river on its downstream during floods by storing
some flood water.
Debris dams: A debris dam is constructed to retain debris such as sand, gravel,
and drift wood flowing in the river with water. The water after passing over a
debris dam is relatively clear.
Based on structure and design:
Gravity Dam: A gravity dam is a dam constructed from concrete or stone
masonry and designed to hold back water by utilizing the weight of the material
alone to resist the horizontal pressure of water pushing against it. Gravity dams
are designed so that each section of the dam is stable, independent of any other
dam section.
Gravity dam resist water pressure, uplift pressure, pressure due to earthquake,
silt pressure, wave pressure, ice pressure.
Gravity Dam maybe:
Straight gravity dam – It is straight in plan.
Curved gravity plan – It curved in plan.
Curved gravity dam (Arch gravity dam) – It resists the forces acting on it by
combined gravity action (its own weight) and arch action.
Solid gravity dam – Its body consists of a solid mass of masonry or concrete
Hollow gravity dam – It has hollow spaces within its body.
Earth Dams: An earth dam is made of earth (or soil) built up by compacting
successive layers of earth. Earth dam resists the forces exerted upon it mainly
due to shear strength of the soil. Examples of earthfill dam: Rongunsky dam
(Russia) and New Cornelia Dam (USA).

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Rockfill Dams: A rockfill dam is built of rock fragments and boulders of large
size. An impervious membrane is placed on the rockfill on the upstream side to
reduce the seepage through the dam. The membrane is usually made of
cement concrete or asphaltic concrete. The side slopes of rockfill are usually
kept equal to the angle of repose of rock, which is usually taken as 1.4:1 (or
1.3:1). Rockfill dams require foundation stronger than those for earth dams.
Examples of rockfill dam: Mica Dam (Canada) and Chicoasen Dam (Mexico).
Arch Dams: An arch dam is curved in plan, with its convexity towards the
upstream side. They transfer the water pressure and other forces mainly to the
abutments by arch action. An arch dam is quite suitable for narrow canyons with
strong flanks which are capable of resisting the thrust produced by the arch
action. The section of an arch dam is approximately triangular like a gravity dam
but the section is comparatively thinner. The arch dam may have a single
curvature or double curvature in the vertical plane. Generally, the arch dams of
double curvature are more economical and are used in practice. Examples of
Arch dam: Hoover Dam (USA) and Idukki Dam (India).
Uttress Dams: Buttress dams are of three types: (i) Deck type, (ii) Multiple-arch
type, and (iii) Massive-head type.
Buttress Dam: A buttress dam is a dam with a solid, water-tight upstream side
that is supported at intervals on the downstream side by a series
of buttresses or supports. The dam wall may be straight or curved. Most
buttress dams are made of reinforced concrete and are heavy, pushing the dam
into the ground. Water pushes against the dam, but the buttresses are inflexible
and prevent the dam from falling over.
Steel Dams: Dams: A steel dam consists of a steel framework, with a steel skin
plate on its upstream face, rather than the more
common masonry, earthworks, concrete or timber construction materials.
Timber Dams: Main load-carrying structural elements of timber dam are made
of wood, primarily coniferous varieties such as pine and fir.
Rubber Dams: A symbol of sophistication and simple and efficient design, this
most recent type of dam uses huge cylindrical shells made of special synthetic
rubber and inflated by either compressed air or pressurized water. Rubber dams

6. 6
offer ease of construction, operation and decommissioning in tight schedules.
These can be deflated when pressure is released.
Principle of working of thermal power plant:
A thermal power plant basically operates on the Rankine cycle. Coal is burnt in
a boiler, which converts water into steam. The steam is expanded in a turbine,
which produces mechanical power driving the alternator coupled to the turbine.
The steam after expansion in prime mover (turbine) is usually condensed in a
condenser to be fed into the boiler again.
The working of modern coal-fired thermal power plant can be studied
conveniently with the help of various cycles. The entire arrangement for sake of
simplicity may be divided into four main circuits namely
(i) Fuel and ash circuit (ii) Air and fuel gas circuit (iii) Feed water and steam
circuit and (iv) Cooling water circuit.
(i) Coal and Ash
Circuit: In this circuit,
the coal from the
storage is fed to the
boiler through coal
handling equipment
for the generation of
steam. Ash produced
due to combustion of
coal is removed to ash
storage through ash-
handling system.
(ii) Air and Gas
Circuit: Air is supplied
to the combustion
chamber of the boiler
either through forced draught or induced draught fan or by using both. The dust
from the air is removed before supplying to the combustion chamber. The

7. 7
exhaust gases carrying sufficient quantity of heat and ash are passed through
the air-heater where the exhaust heat of the gases is given to the air and then it
is passed through the dust collectors where most of the dust is removed before
exhausting the gases to the atmosphere.
(iii) Feed Water and Steam Circuit: The steam generated in the boiler is fed to
the steam prime mover to develop the power. The steam coming out of the
prime mover is condensed in the condenser and then fed to the boiler with the
help of pump. The condensate is heated in the feed-heaters using the steam
tapped from different points of the turbine. The feed heaters may be of mixed
type or indirect heating type. Some of the steam and water are lost passing
through different components of the system, therefore, feed water is supplied
from external source to compensate this loss. The feed water supplied from
external source to compensate the loss. The feed water supplied from external
source is passed through the purifying plant to reduce to reduce dissolve salts
to an acceptable level. This purification is necessary to avoid the scaling of the
boiler tubes.
(iv) Cooling Water Circuit: The quantity of cooling water required to condense
the steam is considerably high and it is taken from a lake, river or sea. At the
Columbia thermal power plant it is taken from an artificial lake created near the
plant. The water is pumped in by means of pumps and the hot water after
condensing the steam is cooled before sending back into the pond by means of
cooling towers. This is done when there is not adequate natural water available
close to the power plant. This is a closed system where the water goes to the
pond and is re circulated back into the power plant. Generally open systems like
rivers are more economical than closed systems.

8. 8
Choice of site and other geographical arrangements for hydro-electric
plant:
(i) Availability of water: Since the primary requirement of a hydro-
electric power station is the availability of huge quantity of water, such
plants should be built at a place (e.g., river, canal) where adequate
water is available at a good head.
(ii) Storage of water: There are wide variations in water supply from a
river or canal during the year. This makes it necessary to store water by
constructing a dam in order to ensure the generation of power
throughout the year. The storage helps in equalising the flow of water so
that any excess quantity of water at a certain period of the year can be
made available during times of very low flow in the river. This leads to
the conclusion that site selected for a hydro-electric plant should provide
adequate facilities for erecting a dam and storage of water.
(iii) Cost and type of land: The land for the construction of the plant
should be available at a reasonable price. Further, the bearing capacity
of the ground should be adequate to with- stand the weight of heavy
equipment to be installed.
(iv) Transportation facilities: The site selected for a hydro-electric
plant should be accessible by rail and road so that necessary equipment
and machinery could be easily transported.
(v) Water pollution: Polluted water may cause excessive corrosion and
damage to metallic structures. This may render the operation of the plant
unreliable and uneconomic.
(vi) Geological Investigation: Geological investigations are needed to see
that the foundation rock for the dam and other structure is firm, stable,
impervious and strong enough to withstand water thrust and other stresses.
(vii) Earthquakes and Seismicity: The area should be free from earthquakes.
(vii) High average rain fall: The Dam should be selected at that place where
there should be high average rain fall.

9. 9
Various types of power plants and its efficiencies:
Efficiencies Thermal
power
plant
Hydro
power
plant
Diesel
Power
Plant
Nuclear
power
plant
Overall
Efficiency
Least
efficient
Most
Efficient
More
efficient
than
thermal
power plant
More
efficient
than
thermal
power plant
overall
efficiency is
about 25%
Overall
efficiency is
about 85%
Efficiency is
about 35%
Efficiency is
in the range
of 38%
Principle of working of hydroelectric power plant:
In hydroelectric power plants the potential energy of water due to its high
location is converted into electrical energy. The total power generation capacity
of the hydroelectric power plants depends on the head of water and volume of
water flowing towards the water turbine. The dam is built across the large river
that has sufficient quantity of water throughout the river. In certain cases where
the river is very large, more than one dam can built across the river at different
locations.
The water flowing in the river possesses two type of energy:
(1) The kinetic energy due to flow of water and
(2) Potential energy due to the height of water.
In hydroelectric power and potential energy of water is utilized to generate
electricity.
More the head of water more is the power produced in the hydroelectric power
plant. To obtain the high head of water the reservoir of water should as high as
possible and power generation unit should be as low as possible. The
maximum height of reservoir of water is fixed by natural factors like the height of
river bed, the amount of water and other environmental factors. The location of

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the power generation unit can be adjusted as per the total amount of power that
is to be generated. Usually the power generation unit is constructed at levels
lower than ground level so as to get the maximum head of water. The total flow
rate of water can be adjusted through the pen stock as per the requirements. If
more power is to be generated more water can be allowed to flow through it.
Turbine:
A turbine is a machine which converts rotational energy from fluids into
mechanical energy of a rotating shaft which drives an alternator.
Types of Turbines:
1. Steam turbines: Most power plants use coal, natural gas, oil or a nuclear
reactor to create steam. The steam runs through a huge and very carefully
designed multi-stage turbine to spin an output shaft that drives the plant's
generator.
2. Gas turbines: A gas turbine, also called a combustion turbine, is a type
of internal combustion engine. It has an upstream
rotating compressor coupled to a downstream turbine, and a combustion
chamber in between.
3. Transonic turbine: The gas flow in most turbines employed in gas turbine
engines remains subsonic throughout the expansion process. In a
transonic turbine the gas flow becomes supersonic as it exits the nozzle
guide vanes, although the downstream velocities normally become
subsonic. Transonic turbines operate at a higher pressure ratio than
normal but are usually less efficient and uncommon.
4. Contra-rotating turbines: A contra-rotating steam turbine, usually known as
the Ljungström turbine. he design is essentially a multi-stage radial turbine
offering great efficiency, four times as large heat drop per stage as in the
reaction turbine, extremely compact design and the type met particular
success in back pressure power plants.

11. 11
5. Ceramic turbine: Conventional high-pressure turbine blades are made from
nickel based alloys and often utilise intricate internal air-cooling passages
to prevent the metal from overheating. In recent years, experimental
ceramic blades have been manufactured and tested in gas turbines, with a
view to increasing rotor inlet temperatures and possibly, eliminating air
cooling.
6. Shrouded turbine: Many turbine rotor blades have shrouding at the top,
which interlocks with that of adjacent blades, to increase damping and
thereby reduce blade flutter. In large land-based electricity generation
steam turbines, the shrouding is often complemented, especially in the
long blades of a low-pressure turbine, with lacing wires. These wires pass
through holes drilled in the blades at suitable distances from the blade root
and are usually brazed to the blades at the point where they pass through.
Lacing wires reduce blade flutter in the central part of the blades. The
introduction of lacing wires substantially reduces the instances of blade
failure in large or low-pressure turbines.
7. Bladeless turbine: It uses the boundary layer effect and not a fluid
impinging upon the blades as in a conventional turbine.
8. Water turbines:
a. Pelton turbine, a type of impulse water turbine.
b. Francis turbine, a type of widely used water turbine.
c. Kaplan turbine, a variation of the Francis Turbine.
d. Turgo turbine, a modified form of the Pelton wheel.
e. Cross-flow turbine, also known as Banki-Michell turbine, or Ossberger
turbine.
9. Wind turbine: These normally operate as a single stage without nozzle and
interstage guide vanes. An exception is the Éolienne Bollée, which has a
stator and a rotor.

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Operation of Electric Arc Furnace:
 The scrap is charged commonly from the furnace top.
 The roof with the electrodes is swung aside before the scrap charging.
 The scrap arranged in the charge basket is transferred to the furnace by a
crane and then dropped into the shell.
 Lower voltages are selected for this first part of the operation to protect the
roof and walls from excessive heat and damage from the arcs.
 Once the electrodes have reached the heavy melt at the base of the
furnace and the arcs are shielded by the scrap.
 The voltage can be increased and the electrodes raised slightly,
lengthening the arcs and increase power to the melt.
Water softening and ash handling in thermal power station:
Water softening in thermal power station:
It is used to remove impurities like suspended particles, minerals and biological
impurities.
Equipment for demineralization cum softening plant consists of two streams
each stream with activated carbon filter, acid, cation exchanger and mixed bed
exchanger.
 It is done when hardness alone is a limiting factor
 In thermal power station soluble water impurities are removed with the help
of PAC (Poly Aluminum Chloride)
 And cation-exchange zeolite resin exchanges all hardness ions to reduce
hardness to zero
Ash handling in thermal Power Station:
Ash handling refers to the method of collection, conveying, interim storage and
load out of various types of ash residue left over from solid fuel combustion
processes. The most common types of ash include bottom ash, bed ash, fly ash
and ash clinkers resulting from the combustion of coal, wood and other solid

13. 13
fuels. Ash handling systems may employ pneumatic ash conveying or
mechanical ash conveyors. Electrostatic Precipitator is used in ash handling
plant to remove fly ash.
Parts of Ash Handling System:
 Bottom Ash Handling System
 Coarse Ash (Economizer Ash) handling system
 Air Pre Heater ash handling system
 Fly ash handling system
 Ash slurry disposal system
Use of ash:
 Manufacturing of building materials.
 Making of concrete.
 Manufacturing of cement.
 Road construction etc.
Types of Loads:
A device which taps electrical energy from the electric power system is
called a load on the system. The load may be resistive (e.g., electric
lamp), inductive (e.g., induction motor), capacitive or some combination
of them. The various types of loads on the power system are:
(i) Domestic load. Domestic load consists of lights, fans, refrigerators,
heaters, television, small motors for pumping water etc. Most of the
residential load occurs only for some hours during the day (i.e., 24
hours) e.g., lighting load occurs during night time and domestic appliance
load occurs for only a few hours. For this reason, the load factor is low
(10% to 12%).

14. 14
(ii) Commercial load. Commercial load consists of lighting for shops,
fans and electric appliances used in restaurants etc. This class of load
occurs for more hours during the day as compared to the domestic load.
The commercial load has seasonal variations due to the extensive use
of air- conditioners and space heaters.
(iii) Industrial load. Industrial load consists of load demand by
industries. The magnitude of industrial load depends upon the type of
industry. Thus small scale industry requires load upto 25 kW, medium
scale industry between 25kW and 100 kW and large-scale industry
requires load above 500 kW. Industrial loads are generally not weather
dependent.
(iv) Municipal load. Municipal load consists of street lighting, power
required for water sup- ply and drainage purposes. Street lighting load
is practically constant throughout the hours of the night. For water
supply, water is pumped to overhead tanks by pumps driven by electric
motors. Pumping is carried out during the off-peak period, usually
occurring during the night. This helps to improve the load factor of the
power system.
(v) Irrigation load. This type of load is the electric power needed for
pumps driven by motors to supply water to fields. Generally this type of
load is supplied for 12 hours during night.
(vi) Traction load. This type of load includes tram cars, trolley buses, railways
etc. This class of load has wide variation. During the morning hour, it reaches
peak value because people have to go to their work place. After morning hours,
the load starts decreasing and again rises during evening since the people start
coming to their homes.

15. 15
Four cycles for the principle of working of Diesel engine:
These are the followings:
1.Intake: In this cycle the piston begins at top dead center. The piston
descends from the top of the cylinder to the bottom of the cylinder,
increasing the volume of the cylinder. A mixture of fuel and air is forced by
atmospheric (or greater by some form of air pump) pressure into the
cylinder through the intake port.
2.Compression: with both intake and exhaust valves closed, the piston
returns to the top of the cylinder compressing the air or fuel-air mixture into
the cylinder head.
3.Power: this is the start of the second revolution of the cycle. While the
piston is close to Top Dead Centre, the compressed air–fuel mixture in a
gasoline engine is ignited, by a spark plug in gasoline engines, or which
ignites due to the heat generated by compression in a diesel engine. The
resulting pressure from the combustion of the compressed fuel-air mixture
forces the piston back down toward bottom dead centre.
4.Exhaust: during the exhaust stroke, the piston once again returns to top
dead centre while the exhaust valve is open. This action expels the spent
fuel-air mixture through the exhaust valve(s).
Factors to be considered in deciding the location of nuclear reactor and
nuclear power plant:
The following points should be kept in view while selecting the site for a nuclear
power station :
(i) Availability of water. As sufficient water is required for cooling
purposes, therefore, the plant site should be located where ample
quantity of water is available, e.g., across a river or by sea-side.
(ii) Disposal of waste. The waste produced by fission in a nuclear
power station is generally radioactive which must be disposed off
properly to avoid health hazards. The waste should either be buried in a
deep trench or disposed off in sea quite away from the sea shore.
Therefore, the site selected for such a plant should have adequate
arrangement for the dis- posal of radioactive waste.

16. 16
(iii) Distance from populated areas. The site selected for a nuclear
power station should be quite away from the populated areas as there is
a danger of presence of radioactivity in the atmosphere near the plant.
However, as a precautionary measure, a dome is used in the plant which
does not allow the radioactivity to spread by wind or underground
waterways.
(iv) Transportation facilities. The site selected for a nuclear power
station should have adequate facilities in order to transport the heavy
equipment during erection and to facilitate the move- ment of the workers
employed in the plant.
(v) Security and Safety: The security to protect atomic material from
terrorist.
(vii) Seismic and Geologic Sitting Criteria: The location nature according
investigations should be free from geologic and seismic problems which
are necessary to determine site suitability and to provide reasonable
assurance.
From the above mentioned factors it becomes apparent that ideal
choice for a nuclear power station would be near sea or river and away
from thickly populated areas.
Method used for earthing the power system neutral:
There are the followings
methods for Neutral earthing:
1. Underground Neutral
Earthing System: In
ungrounded system there
is no internal connection
between the conductors
and earth. However, as
system, a capacitive
coupling exists between
the system conductors and
the adjacent grounded

17. 17
surfaces. Consequently, the “ungrounded system” is, in reality, a
“capacitive grounded system” by virtue of the distributed capacitance.
Under normal operating conditions, this distributed capacitance causes no
problems. In fact, it is beneficial because it establishes, in effect, a neutral
point for the system; As a result, the phase conductors are stressed at
only line-to-neutral voltage above ground.
But problems can rise in ground fault conditions. A ground fault on one
line results in full line-to-line voltage appearing throughout the system.
Thus, a voltage 1.73 times the normal voltage is present on all insulation
in the system.
This situation can often cause failures in older motors and transformers,
due to insulation breakdown.
2. Solid Neutral Earthed System: “When the
neutral point of a 3-phase system (e.g. 3-phase
generator,3-phase transformer etc.) is directly
connected to earth (i.e. soil) through a wire of
negligible resistance and reactance, it is called
solid grounding or effective grounding.”
In this method neutral point is always grounded.
3. Resistance Neutral Earthing System:
When the neutral point of a 3-phase
system (e.g. 3-phase generator, 3-
phase transformer etc.) is connected to
earth (i.e. soil) through a resistor, it is
called resistance grounding.
 Fig. Shows the grounding of
neutral point through a resistor R.
 The value of R should neither be very low nor very high.
 If the value of earthing resistance R is very low, the earth fault
current will be large and the system becomes similar to the solid
grounding system.
 On the other hand, if the earthing resistance R is very high, the
system conditions become similar to ungrounded System.
 The value of R is so chosen such that the earth fault current is
limited to safe value but still sufficient to permit the operation of earth
fault protection system.

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 In practice, that value of R is selected that limits the earth fault
current to 2 times the nor-mal full load current of the earthed
generator or transformer.
4. Resonant Neutral Earthing
System: When the value of L
of arc suppression coil is such
that the fault current IF
exactly balances the
capacitive current IC, it is
called resonant grounding.
An arc suppression coil (also called Peterson coil) is an iron-cored coil
connected between the neutral and earth as shown in Fig.
The reactor is provided with tapings to change the inductance of the coil.
By adjusting the tapings on the coil, resonant grounding can be achieved.
Load factor. The ratio of average load to the maximum demand during a given
period is known as load factor i.e.
Load factor =
Average load
Max.demand
If the plant is in operation for T hours,
Load factor =
Average load x T
Max.demand x T
Load factor =
Units generated in T hours
Max.demand x T hours
The load factor may be daily load factor, monthly load factor or annual
load factor if the time period considered is a day or month or year. Load
factor is always less than 1 because average load is smaller than the
maximum demand. The load factor plays key role in determining the
overall cost per unit generated. Higher the load factor of the power
station, lesser* will be the cost per unit generated.
Diversity Factor: The ratio of the sum of individual maximum
demands to the maximum demand on power station is known as
diversity factor i.e.
Diversity factor = Sum of individual max.demands
Max.demand on power station

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A power station supplies load to various types of consumers whose maximum
demands generally do not occur at the same time. Therefore, the maximum
demand on the power station is always less than the sum of individual maximum
demands of the consumers. Obviously, diversity† factor will always be greater
than 1. The greater the diversity factor, the lesser‡ is the cost of generation of
power.
Effect of load factor on cost of energy:
Load factor affects the cost of energy. Higher the load factor, higher will be the
average load. So, No. of units generated for a given period of time for the same
max. demand will be more. Therefore, overall cost per unit of electrical energy
decreases due to distribution of standing charges which are proportional to the
max. demand and independent of units generated.
Diversity factor affects the cost of energy. More is the diversity lesser will be
max. demand due to which installation capacity of plant will be less. Lesser is
the installation capacity lesser will be the capital required for installation. So
lesser will be generation cost. And the fixed charges in the tariff would be less.
Connected load: It is the sum of continuous ratings of all the
equipment’s connected to supply system.
A power station supplies load to thousands of consumers. Each
consumer has certain equipment installed in his premises. The sum of
the continuous ratings of all the equipment’s in the consumer’s premises
is the “connected load” of the consumer. For instance, if a consumer has
connections of five 100-watt lamps and a power point of 500 watts, then
connected load of the consumer is 5 x 100 + 500 = 1000 watts. The sum
of the connected loads of all the consumers is the connected load to the
power station.
Maximum demand: It is the greatest demand of load on the power
station during a given period.
The load on the power station varies from time to time. The maximum of
all the demands that have occurred during a given period (say a day) is
the maximum demand. Thus referring back to the load curve of Fig. 3.2,

20. 20
the maximum demand on the power station during the day is 6 MW and
it occurs at 6 P.M. Maximum demand is generally less than the
connected load because all the consumers do not switch on their
connected load to the system at a time. The knowledge of maxi- mum
demand is very important as it helps in determining the installed capacity
of the station. The station must be capable of meeting the maximum
demand.
Demand factor. It is the ratio of maximum demand on the power station
to its connected load i.e.
Demand factor =
Maximum demand
connected load
The value of demand factor is usually less than 1. It is expected
because maximum demand on the power station is generally less than
the connected load. If the maximum demand on the power station is 80
MW and the connected load is 100 MW, then demand factor = 80/100 =
0·8. The knowledge of demand factor is vital in determining the capacity
of the plant equipment.
Comparison of Hydro and diesel electric station:
Hydroelectric power
station
Diesel electric power
station
Initial cost is very high Initial cost is very low
Running cost is zero, as it
use water which is for free
Running cost is high, as it
use diesel which is not for
free
Power availability may be
affected by seasonal
precipitation
There is no seasonal
precipitation in diesel electric
power station
It does not make pollution in
the environment
It creates pollution in the
environment
In this station water is
renewable fuel source
In this station diesel is non-
renewable source
Require large space Require less space as
compared to hydro power
station

21. 21
Comparison of Boiling water reactor and pressurized water
nuclear reactor:
Boiling water reactor Pressurized water nuclear
reactor
The steam in boiling water
reactor is produced directly
in the reactor core
While the steam in a
pressurized water reactor is
produced in a secondary
system
The pressure of a boiling
water reactor remains
constant which is 1040 psi,
The pressure of a
pressurized boiling reactor
varies from the primary
system to the output steam,
2250 psi then lowered
the steam in a boiling water
reactor, after coming out of
the steam separators,
proceeds to a steam dryer
and then to the turbine
The steam in a pressurized
water reactor after coming
out of the steam separator
proceeds directly to the
turbine
The water is allowed to boil Preventing the water from
actually boiling.
The steam produced in a
boiling water reactor is
radioactive
Whereas the steam
produced in pressurized
water reactor is
nonradioactive.

22. 22
Operation of nuclear power reactor and its control:
 The operation of nuclear power reactor is based on nuclear fission
reaction, 235
U fissions by absorbing a neutron and producing 2 to 3
neutrons, which initiate on average one more fission to make a
controlled chain reaction
 Normal water is used as a moderator to slow the neutrons since
slow neutrons take longer to pass by a U nucleus and have more
time to be absorbed
 The protons in the hydrogen in the water have the same mass as
the neutron and stop them by a billiard ball effect
 The extra neutrons are taken up by protons to form deuterons
 235
U is enriched from its 0.7% in nature to about 3% to produce the
reaction, and is contained in rods in the water
 Boron control rods are inserted to absorb neutrons when it is time
to shut down the reactor
 The hot water is boiled or sent through a heat exchanger to
produce steam. The steam then powers turbines.
Nuclear power reactor can be controlled with control-rods - these are
dense materials which, when dropped down into the reactor, soak up
some of the neutrons that are produced by the nuclear chain
reaction. The consequence of that is that there are fewer neutrons left
to bust open other uranium or fissionable nuclei, and as a result, the
chain reaction is slowed down. By putting the fuel rods in, or drawing
them out, you can speed up or slow down the chain reaction, and
therefore, you can affect how much energy actually comes out of the
reactor.

23. 23
Importance of Wind Energy:
The importance of wind energy is given below:
1) Wind energy is always for free and can be used without any cost.
2) Wind energy is a form of energy which is pollution free and eco-
friendly. It does not release any harmful emissions or pollutants
that enter the atmosphere from using them.
3) It acts as a great way to supply electricity to rural areas.
4) Wind energy is home grown, and local landowners and small
businesses can operate single turbines or clusters of turbines.
5) Wind energy is a renewable resource that can be used forever, as
long as there is wind.
6) Wind energy is the best alternate to the traditional methods of
generating power.
7) Wind is considered a native fuel that does not need to be
transported.
8) Wind energy requires small area of land.
Energy resources: An energy resource is something that can produce heat,
power life, move objects, or produce electricity. Material such as coal, gas, oil,
and wood consumed in generation of power.
Difference between renewable and non-renewable energy resources:
renewable resources Non-renewable resources
Resources that can be
replenished naturally in the
course of time are called
renewable resources.
Nonrenewable resources cannot
be replenished.
It can be used again and again. It can be used once.
We have unlimited supplies of
them.
We have limited supplies of
them, and when these supplies
are gone we will not have any
more.
It is environmental friendly. It makes pollution
Examples: air, water, sunlight,
wind, rain, tides, bio-fuel,
geothermal energy.
Examples: coal, Natural gas, oil,
nuclear fuels

24. 24
Fossil fuel: Fuels formed by natural resources such as anaerobic
decomposition of buried dead organisms. Fossil fuels are the carbon
rich remains of ancient vegetation and other organisms that have
endured intense heat and pressure inside the earth, the age of the
organisms and their resulting fossil fuels is typically millions of years,
but exceeds 2 billion years.
Different types of fossil fuels are: coal, petroleum and natural gas.
Layout of hydroelectric power plant:
:
Examples:

25. 25
List of all types of hydroelectric power plant:
1) Water wheels
2) Hydro power plants
3) Wave energy from oceans
4) Tidal energy
5) Damless hydro power
Based on Quantity of Water Available
1) Run-off river hydro plants with pondage
2) Run-off river hydro plants without pondage
3) Reservoir hydroelectric power plants
Based on the Head of Water Available
1) Low head hydroelectric power plants
2)Medium head hydroelectric power plants
3) High head hydroelectric power plants
Based on the Nature of Load
1) Base load hydroelectric power plants
2) Peak load hydroelectric power plants

26. 26
Difference between Impulse(Pelton) wheel and Reaction (Francis,
Kaplan and Propeller) Turbine
Impulse turbine Reaction turbine
Impulse Turbine operates at high
water heads.
Reaction turbine operate at low
and medium heads.
In Impulse Turbine all hydraulic
energy is converted into kinetic
energy by a nozzle and it is is
the jet so produced which strikes
the runner blades.
In Reaction Turbine only some
amount of the available energy is
converted into kinetic energy
before the fluid enters the
runner.
Water is admitted only in the
form of jets. There may be one
or more jets striking equal
number of buckets
simultaneously.
Water is admitted over the entire
circumference of the runner.
The turbine doesn’t run full and
air has a free access to the
bucket.
Water completely fills at the
passages between the blades
and while flowing between inlet
and outlet sections does work on
the blades.
The turbine is always installed
above the tail race and there is
no draft tube used.
Reaction turbine are generally
connected to the tail race
through a draft tube which is a
gradually expanding passage. It
may be installed below or above
the tail race.
Flow regulation is done by
means of a needle valve fitted
into the nozzle.
The flow regulation in reaction
turbine is carried out by means
of a guide-vane assembly. Other
component parts are scroll
casing, stay ring runner and the
draft tub.
Impulse Turbine have more
hydraulic efficiency.
Reaction Turbine have relatively
less efficiency.
Impulse turbine involves less
maintenance work.
Reaction turbine involves more
maintenance work.
Water flow is tangential direction
to the turbine wheel.
Water flows in radial(Francis)l
and axial(Kaplan) direction to
turbine wheel.

27. 27
Difference between Kaplan turbine and Francis turbine:
Kaplan Turbine Francis Turbine
Water enters the runner
vanes axially and leave
axially hence it is called axial
flow turbine.
Water enters the runner
vanes radially and leaves
axially hence it is called a
mixed flow turbine.
The number of blades in the
runner is generally between
3 and 8.
The number of blades in the
runner is generally between
16 and 24.
Advantages and disadvantages of hydroelectric power plant:
Advantages:
(i) It requires no fuel as water is used for the generation of electrical
energy.
(ii) It is quite neat and clean as no smoke or ash is produced.
(iii) It requires very small running charges because water is the source
of energy which is available free of cost.
(iv) It is comparatively simple in construction and requires less
maintenance.
(v) It does not require a long starting time like a steam power station. In
fact, such plants can be
put into service instantly.
(vi) It is robust and has a longer life.
(vii) Such plants serve many purposes. In addition to the generation of
electrical energy, they
also help in irrigation and controlling floods.
(viii) Although such plants require the attention of highly skilled persons
at the time of construction, yet for operation, a few experienced persons
may do the job well.
Disadvantages:
(i) It involves high capital cost due to construction of dam.
(ii) There is uncertainty about the availability of huge amount of water
due to dependence on
weather conditions.

28. 28
(iii) Skilled and experienced hands are required to build the plant.
(iv) It requires high cost of transmission lines as the plant is located in
hilly areas which are quite
away from the consumers.
Schematic diagram of nuclear power plant:
Function of fuel rod, control rod and moderator:
Function of fuel rod: A long, slender, zirconium metal tube containing
pellets of fissionable material, which
provide fuel for nuclear reactors. Fuel rods are assembled into bundles
called fuel assemblies, which are loaded individually into
the reactor core.
Control rod: Control rods are used in nuclear reactors to control the
fission rate of uranium and plutonium. They are composed of chemical
elements such as boron, silver, indium and cadmium that are capable of
absorbing many neutrons without themselves fissioning.
Moderator: A nuclear power reactor controls the fission chain reaction
by moderating the neutrons and with the use of control rods which may
be inserted in the reactor core to absorb neutrons and slow down the
reaction.

29. 29
List of main and auxiliary equipment’s used in thermal power
station:
1. Coal handling plant
2. Pulverizing plant
3. Draft fans
4. Boiler
5. Ash handling plant
6. Turbine
7. Condenser
8. Cooling towers and ponds
9. Feed water heater
10. Economizer
11. Superheater and Reheater
12. Air preheater
Explanation:
(1) Coal handling plant: The function of coal handling plant is
automatic feeding of coal to the boiler furnace.
A thermal power plant burns enormous amounts of coal.
A 200MW plant may require around 2000 tons of coal daily
(2) Pulverizing plant: In modern thermal power plant , coal is
pulverised i.e. ground to dust like size and carried to the furnace in a
stream of hot air. Pulverising is a means of exposing a large surface
area to the action of oxygen and consequently helping combustion.
Pulverising mills are further classified as:
(i) Contact mill (ii) . Ball mill (iii) .Impact mill
(3) Draft fans: The circulation of air is caused by a difference in
pressure, known as Draft.
Draft is a differential pressure b/w atmosphere and inside the boiler.

30. 30
It is necessary to cause the flow of gases through boiler setting
It may be –
1. Natural draft 2. Mechanical draft
(4) Boiler: A boiler or steam generator is a closed vessel in which water
under pressure, is converted into steam.
It is one of the major components of a thermal power plant
Always designed to absorb maximum amount of heat released in the
process of combustion
Boilers are of two types-
1. Fire tube boiler 2. Water tube boiler
(5) Ash handling plant: The percentage of ash in coal varies from 5%
in good quality coal to about 40% in poor quality coal
Power plants generally use poor quality of coal , thus amount of ash
produced by it is pretty large
A modern 2000MW plant produces about 5000 tons of ash daily
The stations use some conveyor arrangement to carry ash to dump
sites directly or for carrying and loading it to trucks and wagons which
transport it to the site of disposal
(6) Turbine: A steam turbine converts heat energy of steam into
mechanical energy and drives the generator.
(7) Condenser: In thermal power plants, the purpose of a
surface condenser is to condense the exhaust steam from a steam
turbine to obtain maximum efficiency, and also to convert the turbine
exhaust steam into pure water (referred to as steam condensate) so
that it may be reused in the steam generator or boiler as boiler feed
water.

31. 31
(8) Cooling towers and ponds: A condenser needs huge quantity of
water to condense the steam.
Typically a 2000MW plant needs about 1500MGallon of water.
Most plants use a closed cooling system where warm water coming
from condenser is cooled and reused
Small plants use spray ponds and medium and large plants use cooling
towers.
Cooling tower is a steel or concrete hyperbolic structure having a
reservoir at the base for storage of cooled water
(9) Feed water heater: Feed water heating improves overall plant
efficiency.
The dissolved oxygen and carbon dioxide which would otherwise cause
boiler corrosion are removed in feed water heater
Thermal stresses due to cold water entering the boiler drum are
avoided.
Quantity of steam produced by the boiler is increased.
Some other impurities carried by the steam and condensate, due to
corrosion of boiler and condenser are precipitated outside the boiler.
(10) Economizer: Flue gases coming out of the boiler carry lot of heat.
An economiser extracts a part of this heat from flue gases and uses it
for heating feed water. This use of economiser results in saving coal
consumption and higher boiler efficiency
(11) Superheater: Superheater is a component of a steam-generating
unit in which steam, after it has left the boiler drum, is heated above its
saturation temperature. The amount of superheat added to the steam is
influenced by the location, arrangement, and amount of super heater
surface installed, as well as the rating of the boiler. The super heater
may consist of one or more stages of tube banks arranged to effectively

32. 32
transfer heat from the products of combustion. Super heaters are
classified as convection , radiant or combination of these.
(12) Air preheater: After flue gases leave economiser, some further
heat can be extracted from them and used to heat incoming heat.
Cooling of flue gases by 20 degree centigrade increases the plant
efficiency by 1%.
Air preheaters may be of three types
Plate type
Tubular type
Regenerative type
Deaerator: A deaerator is a device that is widely used for the removal
of oxygen and other dissolved gases from the feedwater to steam-
generating boilers.
Techniques used to dissolved gases:
Mainly two types of techniques are used.
1. Reduce the pressure
2. Rise the temperature to saturation
Economizer save coal consumption and higher boiler efficiency in
thermal power plant:
As the name indicates the function of the economizer is to preheat the
boiler feed water before it is introduced into the drum by recovering heat
from the flue gases leaving the boiler.
Temperature inside economizer is about 3150
C.
The heat of economizer and burnt coal combines thus it saves coal
consumption and increased higher boiler efficiency.

33. 33
advantages and disadvantages of thermal power plant:
advantages:
1. The design and layout of the plant are quite simple.
2. It occupies less space as the number and size of the auxiliaries is
small.
3. It can be located at any place.
4. It can be started quickly and can pick up load in a short time.
5. There are no standby losses.
6. It requires less quantity of water for cooling.
7. The overall cost is much less than that of steam power station of
the same capacity.
8. The thermal efficiency of the plant is higher than that of a steam
power station.
9. It requires less operating staff.
Disadvantages:
1. The plant has high running charges as the fuel (i.e., diesel) used is
costly.
2. The plant does not work satisfactorily under overload conditions for
a longer period.
3. The plant can only generate small power.
4. The cost of lubrication is generally high.
5. The maintenance charges are generally high.
6. Air pollution from smoke fumes

34. 34
Tide: Tides are the rise and fall of sea levels caused by the combined
effects of gravitational forces exerted by the Moon, Sun, and rotation of
the Earth.
Working of tidal power plant:
• two method used : Using turbines
• Using pushplates
USING TURBINES:
Production Of Power From Tidal Energy
Step 1: A location has to be found where there is sufficient tidal
changes to create enough energy to power turbines.
Step 2: A dam or barrage is created
Step 3: sluice gates allow the tides to fill the tidal basin
Step 4: water runs over the turbines which is connected to a
generator

35. 35
Wind Turbine: A wind turbine is device that converts the kinetic energy
from the wind into electrical power. Wind turbines, like aircraft propeller
blades, turn in the moving air and power an electric generator that
supplies an electric current.
Simply stated, a wind turbine is the opposite of a fan. Instead of using
electricity to make wind, like a fan, wind turbines use wind to make
electricity. The wind turns the blades, which spin a shaft, which
connects to a generator and makes electricity.
Working of wind turbine:
The energy in the wind turns the propeller-like blades around a rotor.
The pitch of the blades makes optimum use of the wind direction.
The rotor is connected to the main drive shaft, which spins a generator
to create electricity.
Wind turbines are mounted on a tower to capture the most energy. At
30 metres or more above ground, they can take advantage of faster and
less turbulent wind.
Wind turbines can be used to produce electricity for a single home or
building, or they can be connected to an electricity grid for more
widespread electricity distribution.
Solar energy uses in electrical applications:
• Toys, watches, calculators
• Remote lighting systems
• Water pumping
• Water treatment
• Emergency power
• Portable power supplies
• Satellites

36. 36
• Solar cookers
• Vehicle running on solar power
• Charging phones
Inductive and dielectric heating:
Inductive heating: nduction heating is a method of heating conductive material
by subjecting it to an alternating electromagnetic field, usually at frequencies
between 100 and 500 kHz.
Oscillator circuits containing triodes are commonly used to generate the RF
currents.
Typically induction heating is used in pipe welding and induction hardening/heat
treatment.
Dielectric heating:
Dielectric heating (also known as Capacitance heating) is the method of
heating non-conductive materials. The material to be heated is placed
between two electrodes, to which a high-frequency energy source is
connected. The oscillating field passes through the material and as the
field direction changes, the polarization of individual molecules reverses
rapidly, causing friction and hence heat. The higher the frequency, the
greater the movement. Typically, frequencies in the range 5 MHz to 80
MHz are used. This technology is used in Wood Gluing, RF Drying and
Plastic Welding.
Electric furnaces: An electric arc is an electrical breakdown of a gas
resulting from a current flowing through normally nonconductive media
such as air.
An electric arc furnace (EAF) heats charged material by means of an
electric arc.

37. 37
BRAKING SYSTEM in hydropower plant:
 Electrical and Mechanical (auxiliary) braking is used for regular
braking. When hydro generator is disconnected from grid, turbine
wicket gate is closed and rotation speed is reduced down to 50%
of rated value, short-circuiting of main terminals of stator winding
and current supply into rotor winding from brake thyristor converter
occurs.
 When rotation speed reduced down to 5% of rated value, the
mechanical breaking is automatically switched on .In case of
electrical braking system failure, or electrical damage of generator,
the mechanical breaking is automatically switched on, when
rotation speed will become 10% of rated value.