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EE2451

ELECTRICAL ENERGY GENERATION AND
UTILISATION AND CONSERVATION
QUESTION BANK
UNIT 1
GENERATION

1) What are the sources of energy?
Electrical energy is produced from energy available in various forms in nature
...

Conventional methods (With prime movers)
a) Hydro power generation
b) Thermal power generation
c) Nuclear power generation
Non-Conventional methods (Without prime movers)
d) MHD (magneto hydro dynamic) power generation
e) Solar power generation
f) Fuel cells generation
g) Thermo electric generation
h) Thermionic converters
i) Solar cells
j) Wind power generation
k) Geo-thermal energy generation
L) Tidal power generation
3) What are the limitations of conventional energy sources?
1
...
Most of them emit harmful gases contributing to global warming
3
...
Requires large areas
4) How will you classify hydro-electric plants according to nature of load?
Classification according to nature of load
Base load plants
Pear load plants
Pumped storage plants for peak load
...

9) What is the principle of pumped storage scheme?
The basic principle of pumped storage scheme is to convert the surplus electrical energy
generated by a power plant or available in a system in off-peak periods, to hydraulic potential
energy, in order to generate power in periods where the peak demand on the system exceeds the
total available capacity of the generating stations
...

11) What is the function of deaerator in steam power plant?
The function of deaerator is to reduce dissolved oxygen content in the condensate i
...
in the feed
water
...

12) What are the disadvantages of steam power plants?
The disadvantages are
High maintenance and operating cost
...

Requirement of water in huge quantity
...

Troubles from smoke and heat from the plant
...

13) What is nuclear fission?
In nuclear station, heavy elements such as Uranium (U235) or Thorium (Th232) are
subjected to nuclear fission in a special apparatus known as reactor
...

14) What are the components of nuclear reactor?
The nuclear reactor consists of the following basic components
Reactor core
Moderator
Control rods
Coolant
Reflector
Thermal shielding
Reactor vessel
Biological shield
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The demand for coal, oil and gas is reduced which are tending to rise in cost as the stocks
are becoming depleted
...
A 2000MW nuclear plant needs
80 acres whereas thermal stations need about 250 acres of land
...
The operating cost is quite low and once the installation
is completed, the loading of the plant is always operated as a base load plant
...
If mechanical energy is
directly used it is called a wind mil
...
g
...
If mechanical energy is used to generate electrical
energy and then used it is a wind energy converter
...
Winds are essentially caused by the solar heating of the atmosphere
...
Wind as a source of power is very attractive because it is plentiful,
inexhaustible, renewable and non-polluting
...
In large
portion of the world, wind blows for 320 days in a year and this gives them an advantage over
sunlight in direct conversion programmes, operating cost of a wind mill is negligible
...

The ideal maximum efficiency using Froud momentum theory is equal to 59% but an overall
efficiency of 30% could be had due to aerodynamic and other mechanical losses
...
3KW/sq
...

17) What is the principle of MHD power generation?
Direct conversion of kinetic energy of a flowing liquid in to electricity Faradays law of
electro magnetic induction
...
Hot natural supply of water which can produce steam by the hot under
ground magma is exhausted and processed
...
Energy from sun in
the form of heat and light is harnessed
...

20) What is the principle of tidal power generation?
Tidal movements of tides in seas are due to difference in water levels caused by
(1) Gravitational forces between the Sun, moon and the earth and
(2) Rotation of the moon and earth
...

21) What are the advantages of MHD generation?
The advantages are
The conversion efficiency is around 50% to 60%
...

Capital cost is less compared with conventional steam plants
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Economic and reduced fuel consumption
...

Elimination of energy losses
...
It is possible to convert solar
energy directly into electrical energy by means of silicon wafer photo-voltaic cells, also called the
solar cells, without any intermediate thermodynamic cycle
...
5-1volts and a current density of 20-40 mA/sq
...

23) What are the types of collectors used in solar power generation?
Types of collectors
Flat plate collectors(60°C)
Focusing or concentrating collectors
Cylindrical parabolic concentrator (100-200°C)
Paraboloids, Mirror Arrays( <200°C)
24) What is tide?
TIDE is a periodical rise and fall of the water level of sea which are carried by the action of
the sun and moon on thewater of the earth
...

25) What is the function of moderator in nuclear power plant?
A nuclear reactor is a cylindrical stout pressure vessel and houses fuel rods of Uranium,
moderator and control rods
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The moderator consists of graphite rods which enclose the fuel rods
...

26) What are the merits and demerits of tidal power generation?
The advantages of tidal power are
It is free from the problems of uprooting the people and disturbing the ecology balance
...

No extra submerging of land is involved
...
Variations in the tidal
energy available through the lunar day and lunar month different from their solar
counterparts prevent the tidal power from being regularly used in power systems during the
periods of peak demand
...

28) What are the types of wind mills?
Wind energy conversion system are classified into two types,
i) Horizontal axis wind mills
The axis of rotation is horizontal and in the aero turbine, plane is vertical facing the wind
...

29) Define a distributed generation system?

EE2451

ELECTRICAL ENERGY GENERATION AND
UTILISATION AND CONSERVATION

It is a system of modular power generators at are near the customers sites and loads It
potentially provide an economic
value to the consumers as well as the power grid
...
r
...

31) How does islanding of a distributed generation system connected to the grid affect the power
system?
1
...
over and under frequency
3
...
Voltage harmonics
32) What are the effects of a distributed generation system on a power system?
1
...
Affects auto reclosing
3
...
Causes insulation failure
5
...
dc to ac conversion
2
...
e
...

2) Explain the term depreciation
...
In practice, every power station has a useful life ranging from fifteen to
thirty years
...
This reduction in the
value of plant every year is known as annual depreciation
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Load factor is the ratio of average demand to the maximum demand during a certain period
of time and is applicable to both generating equipment and receiving equipment
...

The load curves supply the following information
The variation of the load during different hours of the day
...

The peak of the curve represents the maximum demand on the station on the particular day
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EE2451

ELECTRICAL ENERGY GENERATION AND
UTILISATION AND CONSERVATION

The ratio of the area under the load curve to the total area of the rectangle in which it is
contained gives the load factor
...

Diversity factor is defined as the state of being dissimilar to one another
...

Diversity factor = Sum of individual demands of different units in a group/Maximum demand of the
entire group
The value of diversity factor is always greater than one
...

6) What do you mean by utilisation factor?
It is a measure of the utility of the power plant capacity and is the ratio of maximum demand
to the rated capacity of the power plant
...

Utilization factor = Maximum Demand on the power station/Rated capacity of the power station
A low value of utilization factor indicates that the plant has been installed much in advance
of need
...
If its value
exceeds unity, it means that the load has been carried in excess of rated capacity of the plant
...

The load curve is obtained from the same data as the load curve but the ordinates are
arranged in the order of descending magnitudes
...
Hence the area
under the load duration curve and the load curve are equal
...
Higher the values of load factor and diversity factor, lower will be the overall cost per unit
generated
...
Thus, the standing charges, which are proportional to
maximum demand and independent of number of units generated, can be distributed over a large
number of units supplied and therefore overall cost per unit of electrical energy generated will be
reduced
...

10) What are the methods for determining depreciation charges?
The decrease in the value of the power plant equipment and building due to constant use is
known as depreciation
...

The reduction in the value of the plant every year is known as annual depreciation
...
Therefore a suitable
amount must be set aside every year, so that by the time the plant retires the collected amount by
way of depreciation equals the cost of equipment
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EE2451

ELECTRICAL ENERGY GENERATION AND
UTILISATION AND CONSERVATION

11) What are the objectives of tariff?
Electrical energy is sold at such a rate so that it not only returns the cost but also earns
reasonable profit
...

Recovery of cost of operation, supplies and maintenance of equipment
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A satisfactory return on the total capital investment
...

Energy Audit means studying the energy consumption patternin the utilities or equipments
by obtaining necessary data analyse the same to identify the areas where wastages or loses
occur and suggest methods to avoid wastages or loss and also other consumption measures to
ensure efficient use of energy
...
c motors are of induction type which have low lagging power factor
...
2 to 0
...
8 to 0
...

Arc lamps, electric discharges lamps and industrial heating furnaces operate at low lagging
power factor
...
During low load period, supply voltage is increased which increases the
magnetization current
...

14) Define the term connected load factor
...

15) What are the important points to be taken into consideration while selecting the size and number
of units?
The load on a power station is never constant due to variable demands from time to time
...
The load variation is greater
with a poorer load factor
...
The number and size of the units are selected in such a way that they correctly
fit the station load curve
...
There should be a spare generating unit so that repairs and overhauling
of the working units can be carried out
...

It is the ratio of average demand to plant capacity
17) What is plant use factor?
It is defined as the ratio of kwh generated to the product of plant capacity and number of
hours for which the plant is in operation
...

20) What is the difference between base load and peak load?
The unvarying load which occurs almost thewhole day is known as base load
...

UNIT-III
ILLUMINATION, HEATING AND WELDING
1) Define luminous flux
...
It is
represented by symbol F and is measured in lumens
...

2) What is meant by candle power?
It is defined as the number of lumens given out by the source in a unit solid angle in a given
direction n
...

CP=lumens/ω
3) Define MHCP
...

4) Define utilization factor
...

Utilization factor= Total lumens reaching the working plane/Total lumens given out by the lamp
5) What are the laws of illumination?
Law of Inverse Squares:
Illumination at appoint is inversely proportional to square of its distance from the point
source and directly proportional to the luminous intensity (CP) of the source of light in that
direction
...
If the sphere be replaced by
one of the larger radius, the same total amount of light is spread over a larger area proportional to
the square of the radius
...

6) What is meant by luminance?
It is defined as the luminous intensity per unit projected area of either a surface source of
light or a reflecting surface and is denoted by L
...

It is defined as the ratio of horizontal distance between adjacent lamps and height of their
mountings
...
If
the luminous intensity, i
...
the candle power is measured in a horizontal plane about a vertical axis

EE2451

ELECTRICAL ENERGY GENERATION AND
UTILISATION AND CONSERVATION

and a curve is plotted between candle power and the angular position,a curve is obtained is called as
horizontal polar curve
...
If the
luminous intensity in a vertical plane is plotted against the angular position, a curve known as
vertical polar curve is obtained
...

1
...
Lummer-Brodhun photometer head
There are two types of Lummer Brodhun heads
a) Equality of Brightness type photometer head
b) Contrast type photometer head
10) What are all the sources of light?
According to principle of operation the light sources may be grouped as follows
...
c
...
Due to the persistence of vision, our eyes do not notice this
...
This effect is called stroboscopic effect
...

The ratio of lumens in the beam of a projector to the lumens given out by lamps is called the
beam factor
...
Its values vary from 0
...
6
...

The distribution of the light emitted by lamps is usually controlled to some extent by means
of reflectors and translucent diffusing screens or even lenses
...

High initial cost and poor power factor
...

Light output fluctuates at twice the supply frequency
...

These lamps can be used only in particular position
...

Illumination level
Uniformity of illumination

EE2451

ELECTRICAL ENERGY GENERATION AND
UTILISATION AND CONSERVATION

Colour of light
Shadows
Glare
Mounting height
Spacing of luminaries
Colour of surrounding walls
...

Economical
Cleanliness
Absence of flue gases
Ease of control or adaptation
Automatic protection
Upper limit of temperature
Special heating features
High efficiency of utilisation
Better working conditions
Safety
Heating of non-conducting materials
17) Classify the methods of electric heating
...
Power frequency heating
a
...
Arc heating
i) Direct arc heating
ii) Indirect arc heating
B
...
Induction heating
i) Direct induction heating
ii) Indirect induction heating
b
...
The heat produced due to I2 R loss in the element is transmitted by radiation or convection
to the body to be heated
...

19)
...
e
...
to
dry the wet paint on an object
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EE2451

ELECTRICAL ENERGY GENERATION AND
UTILISATION AND CONSERVATION

20) What are the requirements of a good heating material?
1
...
Low temperature coefficient of ressistance
3
...
Free from oxidation
21) What are the properties of heating element material?
The material of the heating elements should posses the following desirable properties for
efficient operation and long life
...

High melting point: It should have high melting point so that high temperatures can be
produced without jeopardizing the life of the element
...

Low temperature coefficient: It should have a low temperature coefficient so that resistance
remains appreciably constant even with increases of temperature
...

22) What are the causes of failure of heating elements?
Principle causes are
Formation of hot spots
General oxidation of the element and intermittency of operation
Embrittlement caused by grain growth
Contamination of element or corrosion
23) Write short note on infrared heating
...
Heating effect on the charge is
greater since the temperature of the heating element is greater than in the case of resistance heating
...
m can be obtained leading to heat absorption up to
4300 watts/sq
...
This reduces the time taken by various drying process
...
It works on the principle of electromagnetic induction as same as a
transformer
...
c supply is flowing
...
We find that a secondary current is caused to circulate around the outer surface of
the disc
...


27) What is LASER welding?
LASER (Light Amplification by Stimulated Emission of Radiation) welding is a welding
process that uses the heat from a laser beam impinging on the joint
...

UNIT-IV
INDUSTRIAL HEATING AND WELDING
1
...

Cleanliness
Economical
Uniform heating
Cheap furnace
2
...
State Stephan’s law of radiation
In this process heat is transferred by means of heat waves governed by Stephan’s law
4
...
Name the method of temp control in resistance oven
...
of elements
Changing in connection
SCE

Page 115 of 135

ELECTRICAL AND ELECTRONICS ENGINEERING

EE2451

ELECTRICAL ENERGY GENERATION AND
UTILISATION AND CONSERVATION

External series resistance
Changing transformer tappings
Automatic control
6
...
What are the applications of induction heating?
Surface hardening
Annealing
Melting
Tempering
Soldering
8
...

Due to poor magnetic coupling, leakage reactance is high and power factor is low
Low frequency supply is required
9
...
What is induction heating?
Induction heating is a method of providing fast & consistent heating for manufacturing
applications which involved bonding or changing properties of metlal for electrically
conducting materials
...

Microtech's range of induction heating systems are offered for custom built applications
with suitable coils, materials handling solutions with complete automation
11
...
What is meant by direct resistance heating?
In this method opf heating current is passed through the body to be heated
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13
...
the heat produced due to I^2*R loss in the element is transmitted by radiation or convection
to the body to be heated
...
What is the requirement of a good heating material?
High specific resistance
High melting point
Free from oxidation
Low temperature co efficient of resistance
15
...
Strength - the ability to withstand mechanical stress
2
...
Hardness - Resistance to deformation, abrasion, cutting, crushing

EE2451

ELECTRICAL ENERGY GENERATION AND
UTILISATION AND CONSERVATION

4
...
What is annealing in heat treatment?
Annealing consists of heating the steel to or near the critical temperature (Temperature at
which crystalline phase change occurs) to make it suitable for fabrication
...
Stainless steels and high alloy steels generally require annealing because
these steels are more resistant to rolling
...
What is normalizing?
Normalizing consists of heating the steel above the critical temperature and cooling in air
...
Normalizing is used in some plate mills, in the production of large forgings such
as railroad wheels and axles, some bar products
...
What is quenching?
Quenching consists of heating the steel above the critical point and holding at that
temperature for enough time to change the crystalline structure
...
Quenching produces very hard, very brittle steel
...
What is tempering?
Tempering is carried out by preheating previously quenched or normalized steel to a
temperature below the critical range, holding, and then cooling to obtain the desired mechanical
properties
...
Many products that require
hardness and resistance to breakage are quenched and tempered
...
What is dielectric heating?
The process of heating poor conductors of electricity (dielectrics) by- means of highfrequency electrical currents
...
The heat is developed within
the material rather than being brought to it from the outside, and hence the material is heated more
uniformly throughout
...

The wear on the track should be minimum
...

The equipment should be capable of withstanding large temporary loads
...

There should be no interference to the communication lines running along the lines
...

2) Name the various systems of traction
...
Direct steam engine drive
2
...
Steam Electric Drive
4
...
Petrol Electric traction
6
...
Electric Drive
3) Classify the supply system for electric traction
...
D
...
A
...
Composite system
i) Single phase AC-DC
ii) Single phase-Three phase
4) What are the advantages of electric traction?
High starting torque
Less maintenance cost
Cheapest method of traction
Rapid acceleration and braking
Less vibration
Coefficient of adhesion is better
It has great passenger carrying capacity at higher speed
...

The electrically operated vehicles have to move on guided track only
...

Average speed is the ratio of distance between two consecutive stations to time taken to
travel the distance; Scheduled speed is the ratio of distance between two consecutive stations to
total time taken for moving including the time for stops
...
Name the different stages of train movement
1
...
Constant speed or free running
3
...
Retardation, with braking
8) What are the essential features (electrical) of an ideal traction motor?
1
...

2
...
Simple speed control
4
...
To limit starting current
2
...
Both manual and automatic control should be possible
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Of the two, the speed-time
curve is generally used
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The speedtime curve gives the complete information about
the motion of the train
...
Slope of the
curve at any point gives the speed at that instant
...

11) What do you mean by average speed in electric traction?
The mean of the speeds from the start to stop i
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Average speed= Distance between stops in km/Actual time of run in hours
12) What do you mean by schedule speed in electric traction?
The ratio of distance covered between two stops and total time of run including time of stop
is known as schedule speed
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The difference is large in case of urban and suburban services and is negligibly small in case of
main line service
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It is measured in Newtons and is tangential to the driving
wheels
...

14) What are the factors affecting energy consumption?
The various factors affecting energy consumption are
(i) Distance between the stops
The greater the distance between the stops, the lesser will be the specific energy consumption
for suburban service is 50 to 75 watts-hour/ ton-km and for main line service it is between 18 to
32 Watt-hour/ton-km
...
If the train resistance is greater, the
specific energy consumption is more
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(iv) Gradient
The steep gradients will involve more energy consumption though regenerative braking is
applied
...

15) Define dead weight, adhesive weight
...

(ii) Adhesive weight
The total weight to be carried on the driving wheels is known as the adhesive weight
...

There are various methods for controlling the speed of d
...
They are

EE2451

ELECTRICAL ENERGY GENERATION AND
UTILISATION AND CONSERVATION

*Rheostatic control
*Series parallel control
*Field control
*Buck and Boost method
*Metadyne control
*Thyristor control
17) What are the basic requirements of braking system?
The basic requirements of a braking system are given below
It should be simple, robust, quick and reliable in action
...

Maintenance should be minimum
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In case of emergency braking, safety consideration is taken into account
...

18) What are the various methods of applying electric braking?
There are three methods of applying electric braking are
Plugging or Reverse current braking
Rheostatic braking
Regenerative braking
...

The latest methods of speed control of traction motors are
Tap changer control
Thyristor control
Chopper control
Microprocessor control
20) What are the advantages of microprocessor based control of traction motors?
The advantages of microprocessor based drives are
High speed of response
High accuracy
Over voltage and over speed protection
...

Numbers of components used are less

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