ELECTRIC ENERGY GENERATION, UTILISATION AND CONSERVATION Two Mark Question and Answers

1.1 Syllabus

EE2451 ELECTRIC ENERGY GENERATION, UTILISATION AND CONSERVATION 3 0 0 100 

1.  GENERATION    8 

Generation of electrical power by conventional methods – a brief review –
generation from tidal, wind, MHD, geothermal and solar sources – introduction to
the concept of distributed generation – effect on system operation.

2.  CONSERVATION    10 

Economics of generation – definitions – load curves– number and size of units –
cost of electrical energy – tariff – need for electrical energy conservation – methods
– energy efficient equipment – energy management – energy auditing.
Economics of power factor improvement – design for improvement of power factor
using power capacitors – power quality – effect on conservation.

3.  ILLUMINATION, HEATING AND WELDING  10 

Nature of radiation – definition – laws – photometry – lighting calculations – design
of illumination systems (for residential, industrial, commercial, health care, street
lightings, sports, administrative complexes) - types of lamps - energy efficiency
lamps.
Methods of heating, requirement of heating material– design of heating element –
furnaces – welding generator – welding transformer and its characteristics.

4.  ELECTRIC TRACTION    9 

Introduction – requirements of an ideal traction system – supply systems –
mechanics of train movement – traction motors and control – multiple units –
braking – current collection systems – recent trends in electric traction.

5.  DRIVES AND THEIR INDUSTRIAL APPLICATIONS  8 

Introduction – motor selection and related factors – loads – types – characteristics –
steady state and transient characteristics – load equalization – industrial applications
– modern methods of speed control of industrial drives.
L = 45 Total = 45

TEXT BOOKS
1.  E. Openshaw Taylor, ‘Utilization of Electrical Energy in SI Units’, Orient Longman
Pvt.Ltd, 2003.
2. B.R. Gupta, ‘Generation of Electrical Energy’,  Eurasia Publishing House (P) Ltd,
New Delhi, 2003.
REFERENCE BOOKS
1. H. Partab, ‘Art and Science of Utilisation of Electrical Energy’, Dhanpat Rai and
Co, New Delhi, 2004.
2. Gopal.K.Dubey, ‘Fundamentals of Electrical Drives’, Narosa Publishing House,
New Delhi, 2002.
3. C.L. Wadhwa, ‘Generation, Distribution and Utilization of Electrical Energy’, New
Age International Pvt.Ltd, 2003.
4. J.B. Gupta, ‘Utilization of Electric Power and  Electric Traction’, S.K.Kataria and
Sons, 2002.
www.Vidyarthiplus.com
www.Vidyarthiplus.com  Page 3

UNIT – I 

TWO MARKS

1. List out the advantages of nuclear power stationover thermal power station

 The amount of fuel required is very small

 There is no problem of transportation and storage

 Less space is required

 Most economical
2. Name the sub system of solar power plant.

 Solar energy collection system

 Thermal energy transfer system

 Thermal energy storage system

 Energy conversion system
3. Indicate the difficulties in using geo thermal energy

 Overall efficiency of power production is low

 Drilling operation is noisy

 Large areas are needed for exploitation of geo thermal energy
4. State the advantages of interconnected operation of power system

 Increased reliability of supply: in the event of power failure at one station the
supply can be fed from other station

 Reduction in total installed capacity

 Spinning reserve is reduced
5.  State the advantage of MHD

 Conversion efficiency is around 50%

 The closed cycle supply produces power,free of pollution

 It has no moving parts,so more reliable
6. What are the major components of nuclear power?

 Nuclear reactor

 Heat exchanger

 Steam turbine

 Alternator
7. State the principle of DG power plant.
The diesel burns inside the DG and the product of this combustion act as
the fluid to produce the mechanical energy.
8. What are the classifications of wind energy conversion?

 Horizontal axis wind mill

 Vertical axis wind mill
9. Define distributed generation.
It can be defined as the integrated use of small generation units directly
connected to the distribution supply or inside the facilities of a customer

10. What are the effects of system operation?

 Distributed generation

 The small scale production of electricity

 It has the potential to improve the reliability of the power supply

 Cost of electricity is reduced

 Lower emission of air pollutants
11. What are the parameters characterisisng solar concentrators?

 The aperture area

 The acceptance angle

 The absorber area

 Geometrical concentration ratio

 The optical efficiency

 The thermal efficiency
12. What are the advantages of solar concentrator?

 Improved thermal efficiency due to reduced heat loss area

 Increased energy delivery temperature,facilitating their dynamic match
between temperature level and the task

 Increased number of thermal storage options at elevated temperatures,
thereby reducing the storage cost.
13. Name the components of flat plate collector.

 An absorber plate(metallic or plastic)

 Tubes or pipes for conducting or directing the heattransfer fluid

 One or more covers

 Insulation to minimize the downward heat loss from the absorbing plate
14. What are the important factors governing the selection of site for conventional
sources?

 Location of dam

 Choice of dam

 Quantity of water available

 Accessibility of site
15. What are the classifications based on plant capacity in hydro plants?

 Micro hydel plant : less than 5 MW

 Medium capacity palnt : 5 to 100 MW

 High capacity plant : 101 MW to 1000 MW

 Super capacity plant : above 1000 MW
16. What are the classifications of turbine?

 Francis turbine , patened by francis in 1849

 pelton turbine , patened by Pelton in 1889

 Propeller and Kaplan turbine , patened by Kaplan in 1913

 Deraiz turbine ,patened by Deraiz in 1945
17. Define surge tank.
Surge tanks are tanks connected to the water conductor system. It serves the
purpose of reducing water hammering in pipes which can cause damage to pipes.

The sudden surges of water in penstock are taken bythe surge tank, and when the
water requirements increase, it supplies the collected water thereby regulating water
flow and pressure inside the penstock.
18. What is the General Layout of Thermal Power Plant?
The general layout of thermal power plant consists of mainly four circuits as
shown in [1]. The four circuits are

 Coal and Ash circuit

 Air and Gas circuit

 Feed Water and Steam circuit

 Cooling Water circuit
19. What are the Types of Air Heaters and give a brief introduction.

 Tubular Air Heater:
The flue gas flows outside the tubes in which the air flows heating it. To increase
the time of contact horizontal baffles are provided.

 Plate Type Air Heater:
It consists of rectangular flat plates spaced 1.5 to 2 cm apart leaving alternate air
and gas passages. This is not used extensively as it involves high maintenance.
20. Define Economizer:
The economizer is a feed water heater, deriving heat from the flue gases. The
justifiable cost of the economizer depends on the total gain in efficiency. In turn this
depends on the flue gas temperature leaving the boiler and the feed water inlet
temperature.

UNIT – II

PART A

1. Define demand factor.
It is defined as the ratio of max. demand on the power station to its connected
load
2. Define load factor
It is the ratio of average load tothe maximum demand during a given period
3. What is load curve?
A curve showing the load demand of a consumer against time in hours of the day
is known as load curve
4. Draw the load duration curve.
Demand factor = maximum demand / connected load
Load factor = average load / maximum demand

5. What is tariff?
Different methods of charging consumers are known as tariff or rates of payment
for the consumption of electricity.
6. How can we calculate the cost of electricity?

 Sum all the operating expenses for each year of operation - fuel, O&M,
consumables, etc.

 Add the carrying cost of capital – Total capacity xFixed Charge Rate

 Divide by Kwh’s produced in the year

 Yields average annual cost of electricity THB/Kwh
7. What is two part tariff?
When the rate of electrical energy is changed on the basis of maximum demand
on the consumer and the units consumed, then it is called two part tariff.
8. What is energy efficient drive?
The concept of energy efficient design has developsto challenge the efficiency of
induction motor especially for the rating of 37 Kw.
9. Mention the role of energy audit
An energy audit establishes both where and how the energy is being used and
the potential for energy saving.
10. What are the types of energy audit?

 Preliminary energy audit

 Detailed energy audit


11. How to improve the power factor?

 Installing static power capacities

 Operating synchronous motor in one excited condition

 Installing static VAR compensator.
12. Draw the demand charges curve

13. What is meant by flickers?
The variation of input voltage that is insufficient duration to allow visual
vibration of a change in electric light source intensity.
14. Why some utilities have cheaper rates in the evenings?
That's because it's harder for them to reach peak demand during the day when
everyone's running AC. So they might charge less in the evenings to try to get you to
move some of your consumption (like laundry machines) outside of those daytime
hours. And even if your utility doesn't have cheaper rates at night, if you’re utility has a
demand charge it could pay to shift your laundry tothe evenings, because running
laundry + air conditioning at the same time resultsin a higher demand.
15. What is the long term perspective of the priceof electricity?
The price of the Kilo Watt reacted slowly for two reasons which I shall so
summarize:

 Most of the private producers signed contracts of delivery for very long term
(20 - 30 years) for a majority of their production.

 When the production of electricity is dealt with bynationalized producers,
the State prevents the prices from rising too fast by subsidizing more or
less directly.

 Nevertheless, both positions can be only temporary,because a private
company cannot produce infinitely at a loss and a State cannot pay ad
Vitam æternam charges her of electricity of her taxpayers.
16. What is the capital cost of power plant?
This includes the cost of land, building, and equipment installation, designing
and planning of the plant. It depends upon the typeand location of plant.
17. What are the economics nuclear power plants?

 Nuclear power is cost competitive with other forms of electricity
generation, except where there is direct access to low-cost fossil fuels.

 Fuel costs for nuclear plants are a minor proportion of total generating
costs, though capital costs are greater than those for coal-fired plants and
much greater than those for gas-fired plants.

 Ste disposal costs are taken into account.

18. What is financing cost?
Financing costswill depend on the rate of interest on debt, the debt-equity ratio, and
if it is regulated, how the capital costs are recovered.
19. What is operating cost?
Operating costs include operating and maintenance (O&M) plus fuel, and need to
allow for a return on equity.
20. What is meant by depreciation?
The wear and tear of the equipment with use, the corrosion and ageing of
metals and the deterioration of insulation with time, will reduce the cost of the
equipment

UNIT – III 

TWO MARKS

1. State the advantages of electric heating.

 Cleanliness

 Economical

 Uniform heating

 Cheap furnace
2. What are the modes of heat transfer?

 Conduction

 Convection

 Radiation
3. State Stephan’s law of radiation
In this process heat is transferred by means of heat waves governed by
Stephan’s law
4. What are the properties of heating element material?

 High specific resistance ---- free from oxidation

 High melting point -----------small temp coefficient
5. Name the method of temp control in resistance oven.

 By varying the no. of elements

 Changing in connection

 External series resistance

 Changing transformer tappings

 Automatic control
6. How electric heating is classified?

 Resistance heating

 Induction heating

7. What are the applications of induction heating?

 Surface hardening

 Annealing

 Melting

 Tempering

 Soldering
8. Mention few draw backs of core type furnace.

 Due to poor magnetic coupling , leakage reactance is high and power
factor is low

 Low frequency supply is required
9. State the advantage of core less induction furnace

 Time taken to reach the melting temp is less

 There is no smoke and noise
10. 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.

 Todays advanced design concepts warrant most engineering
components to be heated to either from different shapes or attain
specific grain structures.

 Microtech's range of induction heating systems are offered for custom
built applications with suitable coils, materials handling solutions with
complete automation
11. What are the classifications of power frequency method?

 Direct resistance heating

 Indirect resistance heating

 Direct arc heating

 Indirect arc heating
12. What is meant by direct resistance heating/
In this method opf heating current is passed through the body to be
heated.the resistance offered by the body to the flow of current produces ohmic loss which
results in heating the body.
13. What is meant by indirect resistance heating/
In this method the current isproduced through a high resistance wire known
as heating element.the heat produced due to I^2*R loss in the element is transmitted by
radiation or convection to the body to be heated.
14. 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. What are the properties of steel?

 Strength- the ability to withstand mechanical stress

 Ductility- Ability to be formed without rupture

 Hardness- Resistance to deformation, abrasion, cutting, crushing

 Toughness- ability to absorb shock without breaking
16. 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. Annealing is performed to soften steelafter cold rolling, before surface
coating and rolling, after drawing wired rod or cold drawing seamless tube. Stainless
steels and high alloy steels generally require annealing because these steels are more
resistant to rolling.
17. What is normalizing?
Normalizing consists of heating the steel above thecritical temperature and
cooling in air. This treatment refines the grain size and improves the uniformity of
microstructure and properties of hot rolled steel. Normalizing is used in some plate
mills, in the production of large forgings such as railroad wheels and axles, some bar
products.
18. 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. This heat is followed
by quenching in a water or oil bath to bring the steel back through the critical
temperature range without further changes to the microstructure. Quenching produces
very hard, very brittle steel.
19. 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. Tempering is used to reduce the brittleness of quenched steel.
Many products that require hardness and resistance to breakage are quenched and
tempered.
20. What is dielectric heating?
The process of heating poor conductors of electricity (dielectrics) by- means of
high-frequency electrical currents. The thermoplastic composite to be heated forms the
dielectric of a condenser to which is applied a high-frequency (20-to-80 mc) voltage.
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.

UNIT-IV 

TWO MARKS

1. What are the applications of dc series motor?


 The series DC motor is an industry workhorse for high and low power, fixed
and variable speed electric drives. Applications range from cheap toys to
automotive applications.

 They are inexpensive to manufacture and are used invariable speed household
appliances such as sewing machines and power tools.

 Its high starting torque makes it particularly suitable for a wide range of
traction applications.
2. Name the sub system of solar power plant.

 Solar energy collection system

 Thermal energy transfer system

 Thermal energy storage system

 Energy conversion system
3. Indicate the difficulties in using geo thermal energy

 Overall efficiency of power production is low

 Drilling operation is noisy

 Large areas are needed for exploitation of geo thermal energy
4. State the advantages of interconnected operation of power system

 Increased reliability of supply: in the event of power failure at one station the
supply can be fed from other station

 Reduction in total installed capacity

 Spinning reserve is reduced
5. What is tariff?
Different methods of charging consumers are known as tariff or rates of payment
for the consumption of electricity.
6. How can we calculate the cost of electricity?

 Sum all the operating expenses for each year of operation - fuel, O&M,
consumables, etc.

 Add the carrying cost of capital – Total capacity xFixed Charge Rate

 Divide by Kwh’s produced in the year

 Yields average annual cost of electricity THB/Kwh
7. What is two part tariff?
When the rate of electrical energy is changed on the basis of maximum demand on
the consumer and the units consumed, then it is called two part tariff.
8. What is energy efficient drive?
The concept of energy efficient design has develops to challenge the efficiency of
induction motor especially for the rating of 37 Kw.
9. State the advantage of core less induction furnace


 Time taken to reach the melting temp is less

 There is no smoke and noise
10. 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.
11. What is plane angle?
A plane angle is subtended at a point and is enclosed by two straight lines lying in
the same plane. A plane angle is expressed in termsof degrees or radian.A radian is the
angle subtended by an arc of a circle whose length equals the radius of the circle.
12. Define illumination.
Illuminance is the total luminous fluxincident on a surface, per unit area. It is a
measure of the intensity of the incident light, wavelength-weighted by the luminosity
functionto correlate with human brightness perception. Similarly, luminous emittance
is the luminous flux per unit area emitted from a surface. Luminous emittance is also
known as luminous exitance
13. What are the several strategies available to minimize energy requirements in any
building?

 Specification of illuminationrequirements for each given use area. Analysis of
lighting quality to insure that adverse components of lighting (for example, glare
or incorrectcolor spectrum) are not biasing the design.

 Integration of space planning and interior architecture (including choice of interior
surfaces and room geometries) to lighting design.

 Design of time of day use that does not expend unnecessary energy. Selection of
fixtureand lamp types that reflect best available technology forenergy
conservation.

 Training of building occupants to utilize lighting equipment in most efficient
manner.
14. State illumination law.
Frechner’s Law states that the same percentage change in stimulus calculated
from the least amount perceptible gives the same change in sensation. Inverse Square
Law states that the intensity of illuminationproduced by a point source varies
inversely as square of the distance from the source.
15. Define solid angle.
A concept which frequently is used for illumination calculation is the solid
angle.
Solid angle subtended by area = area of inter section at sphere surface / (radius of sphere)^2
16. Define luminous flux.
It is the rate of energy radiation in the form of light waves and is denoted by  Φ=
Q / t. where Q is the radiant energy. Its unit is lumen.
17. Define lumen.
One lumen is defined as the luminous flux emitted by a source of one candle
power in a solid angle.

Lumen = candle power of source * solid angle
18. Define candle power.
It is defined as the no. of lumens emitted by that source per unit solid angle in a
given direction. The term candle power is used interchangeably with intensity.
19. What are the classifications of lighting?

 Lighting is classified by intended use as general, localized, or task lighting,
depending largely on the distribution of the light produced by the fixture.

 Task lightingIs mainly functional and is usually the most concentrated, for
purposes such as readingor inspectionof materials. For example, reading poor-quality reproductions may require task lighting levels up to 1500 lux(150
footcandles), and some inspection tasks or surgicalprocedures require even higher
levels.

 Accent lightingis mainly decorative, intended to highlight pictures, plants, or
other elements of interior designor landscaping.

 General lighting fills in between the two and is intended for general illumination
of an area. Indoors, this would be a basic lampon a table or floor, or a fixture on
the ceiling. Outdoors, general lighting for a parking lotmay be as low as 10-20
lux (1-2 footcandles) since pedestriansand motoristsalready used to the dark will
need little light for crossing the area.
20. What are the several factor caused by Over-illumination

 Not using timers, occupancy sensorsor other controls to extinguish lighting
when not needed

 Improper design, especially of workplacespaces, by specifying higher levels of
light than needed for a given task

 Incorrect choice of fixturesor light bulbs, which do not direct light into areas as
needed

 Improper selection of hardware to utilize more energy than needed to accomplish
the lighting task

UNIT – V 

TWO MARKS

1. Classify an electric drive.

 Group drive

 Individual drive

 Multi motor drive
2. What are the factors affecting selection of motor?

 Electrical characteristics

 Size of motor

 Mechanical factors

 Cost

3. What are the factors to be considered in size of motor?

 Continuous rating

 Variable load rating

 Over load capacity

 Pull out torque
4. What are the mechanical factors?

 Type of enclosure

 Rearings

 Transmission of drive

 Noise level
5. Write the nature of mechanical load.

 Constant load torque

 Load torque αspeed

 Load torque αspeed ^2

 Load torque α1/speed
6. Classify the load torque depending upon the time.

 Continuous and constant load

 Continuous but vaiable loads

 Pulsating loads

 Impact loads

 Short time intermittent
7. What are the essential requirements of a satisfactory braking?

 It should be fast , reliable and controllable

 The stored energy of rotating parts should be dissipated through suitable means.

 A failure of any part of the braking system should result in braking only.
8. What are the three methods of electrical braking?

 Plugging or counter current braking

 Rheostatic braking

 Regenerative braking
9. What is mechanical or friction braking?
It is the braking in which the storedenergy of the rotating parts is dissipated as
heat by a brake shoe or band rubbing on a wheel or brake drum.
10. State the working of dynamic or rheostatic braking.
In this method the motor is disconnected from the supply and is used as a
generator, driven by the momentum of the equipment to be broken, the electric energy
so generated is dissipated as in external resistors. This method can be used for dc,
induction and synchronous motors.
11. State the two advantages of electric drive.

 Electric drives are adaptable to any type of load requirement


 There is a wider variety of electric motors, which can be designed exactly
according to load requirements.
12. What is an individual drive?
A single electric motor is used todrive one individual machine though its cost is
more than group drive but each operator has complete control of his machine which
will enable.
13. Define continuous rating of motor.
It is that output which a motor can give continuously for long time without
exceeding the given temperature riseand motor should be 20% overload for 2 hours.
14. Write the torque equation of a dc motor.
Where: T = Torque, lb-ft
F = Force, lb
R = Radius, or distance which force is applied frompivot location, ft
15. Write the formula to determine a fan or blowers horsepower.
Equation: Where T = Required Torque, lb-ft
WK
2
= Inertia of load to be accelerated   = Change of speed,
rpm
t = Time to accelerate the load, seconds
16. What are the four important functions in a hybrid vehicle application?

 It enables the "start-stop" function, turning off the engine when the vehicle is
stationary saving fuel.

 It generates the electrical energy to power all theelectrical ancillaries.

 It provides a power boost to assist the engine whenrequired, permitting smaller
engines for similar performance.

 In some configurations it recuperates energy from regenerative braking.
17. What is reluctance torque?
Torque is created due to the reaction between magnetic fields. Consider a
small bar magnet in the field of another larger magnet such as the gap between the
poles of a horse shoe magnet or one of the pole pairs of an electric motor. When the
bar magnet is aligned with the poles of the large magnet its field will be in line with
the external field. This is an equilibrium positionand the bar will not experience any
force to move it. However if the bar is misaligned with the poles, either rotated or
displaced, it will experience a force pulling it back into line with the external field. In
the case of a lateral displacement, the force diminishes as the distance increases, but in
the case of a rotation, the force will increase reaching a maximum when the bar is at
Equation: T = FR

right angles to the external field. In other words the torque on the magnet is at a
maximum when the fields are orthogonal and zero when the field are aligned.
18. Define torque angle.
Even in synchronous motors in which the rotor turns at the same speed as the
flux wave, because of the losses noted above the rotor poles will never reach complete
alignment with the peaks in the flux wave, and there will still be a displacement
between the rotating flux wave and the rotating field. Otherwise there would be no
torque. This displacement is called the "torque angle". The motor torque is zero when
the torque angle is zero and is at its maximum whenthe torque angle is 90 degrees. If
the torque angle exceeds 90 degrees the rotor will pull out of synchronism and stop.
19. Write the characteristics of motor.
Torquegenerally speaking the torque produced by a motor is proportional to the
current it consumes and also proportional to the flux in the air gap.
T = K1I B
Speed
o  In DC motors the rotational speed is proportional to the applied voltage. The
speed is however inversely proportional to the fluxin the air gap.
In AC motors the speed is proportional to the frequency of the applied voltage and
inversely proportional to the number of magnetic poles.
20. What is cogging?
Cogging is the jerky, non uniform angular velocity of a machine rotor particularly
apparent at low speeds in motors with a small number of poles. It occurs because the
rotor tends to speed up as it approaches the statorpoles and to slow down as it leaves
the poles. It is also noticeable when pulsed DC is used if the frequency of the supply
waveform is too low. The problem can be reduced by using skewed rotor windings as
well as increasing the number of poles in the motor.