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POWER SYSTEM - II

One mark Question Answer for VI Semester EEE

L- Scheme

Prepared by

Senthil G. Kumar

Vice Principal & HOD/EEE

Ranganathan Polytechnic College

Coimbatore 641109.


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POWER SYSTEMII DEPARTMENT OF ELECTRICAL & ELECTRONICS ENGINEERING

Prepared by Senthil G. Kumar, Vice Principal, Ranganathan Polytechnic College, Coimbatore109.

UNIT- I : DISTRIBUTION

1. What are the major parts in a distribution system?

Feeder

DistributerService Main

2. What is a feeder?

Feeder is nothing but a conductor which is used to connect the

substation with a particular distributer. There is no tapping in Feeder.

3. Name the two types of AC distribution system?

Primary Distribution System

Secondary Distribution System

4. Classify the distribution system based on connection.

Radial Distribution System

Ring Main Distribution System

Interconnected Distribution System

5. Write any two advantages of radial system.

Initial cost is Low.

Circuit is simple.

6. List down the various systems of power distribution.

DC system

Single phase AC system

Two phase AC system

Three phase AC system

7. What is meant by substation?

Substation is a system having the apparatuses like Power Transformer,

Isolators, which are used to transmit the power in continuously.


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8. What are the assumptions to be made while comparing the cost of

conductors of an OH system?

Power in each system must be equal

Distance of Power transmission in each system is same.

Losses in each system must be same.The Maximum voltage across Line and Earth of all system must be

same.

Balanced Load in Three wire system is must.

9. Name the classification of substation.

Transformer substation

Switching substation

Converting substation

Industrial substation

10. Write down the substation according to constructional features.

Indoor substation

Outdoor substation

Underground substation

11. List out the disadvantages of outdoor substation.

Construction is Simple.

Initial cost for construct the equipments are low.

Time required to construct this substation is less.

12. Name the important equipments used in substation.

Bus Bar

Power Transformer

Circuit Breakers

InsulatorsMeasuring Instruments

Isolators

Instruments Transformer

Lightning Arresters.


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13. What are the different types of bus bar arrangements?

Single Bus bar arrangement

Double Bus bar arrangement

Ring Bus bar arrangement

14. List any two auxiliary equipments in substation.

Emergency Lighting

Measuring Instruments and Relays

15. Write the important points to be considered while laying out a

substation.

Substation is constructed nearby Load Centre.

It has minimum Initial cost.

It should be operate and maintain in simple.

The construction should be Reliable.

16. What is the cost of AC 3 3wire system with 2wire DC system?

Cost of AC 3 3wire system is ( 0.5 /Cos2 ) times that of 2 wire DC

system.

17. Differentiate radial and ring distribution system?

Radial distribution system Ring main distribution systemThe distributor nearby Feeder takesmaximum Load. So, Voltagefluctuation is more.

Voltage fluctuation is Less.

Consumer depends on one Feederand distributer. If any fault on themtotal supply to consumer may cutoff.

Each distributor has two Feederconnections. So, Fault of one feedercannot affect the continuity ofPower to consumer. It is more

reliable.

18. List the main advantage of Interconnected System.

Load sharing to nearby Generating station is possible at Peak Load

period.


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19. List the main disadvantage Ring bus bar system.

Establish new connections are very hard process.

Any one circuit breaker is open, then the total circuit has over Load.

20. List the types of Outdoor substation.Pole mounted Substation & Foundation mounted substation.


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UNIT- II : INDUSTRIAL DRIVES

1. What is meant by electric drive?

Electrical drive means the drive delivers mechanical output by electrical

input.

2. What are the advantages of electric drives over other drives?

Simple in construction & Maintenance cost is low.

Smooth and easy speed control can be obtained.

Pollution free and Less space required.

3. Name the important parts of an electric drives.

Load

Motor &

Control Unit.

4. State the different types of electric drives.

Individual drive

Group drive

Multimotor drive

5. What are the advantages of group drive?

Initial cost is lower than individual drive.

All works can be stop at a time.

Less space required than individual drive.

Maintenance cost also lower than individual drive.

6. List down the classification at electric motors.

A.C Motors

o Single phase ac motorso Three phase ac motors

D.C Motors

o DC Series Motors

o DC Shunt Motors

o DC Compound Motors


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7. Draw the speed- torque characteristics curve of DC shunt motor.

8. Draw the running characteristics of universal motor.

9. What are the factors to be considered for selection of motors?

Starting Characteristics

Running Characteristics

Speed Control

Braking

10.Name the different types of enclosures used in motors?

Open type enclosures

Screen protected type enclosures

Drip proof type enclosures

Totally enclosed type enclosures

Splash proof type enclosures

Flame proof type enclosures Pipe ventilated type enclosures

11.Write down the uses of bearing.

Bearing is used to reduce the friction of rotating Machine and used to

rotate freely.


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12.Name the different types of transmission drives.

Direct drive

Belt drive

Rope driveChain drive

Gear drive

13.What is meant by continuous rating?

A motor delivers continues output without exceeding its rated temperature

is known as continuous rating.

14.What is meant by regenerative braking?Motor acts as a generator and the power supply is feedback to mains and

a braking torque is obtained to brake the motor is known as regenerative

braking.

15.State which type of motor in used for Cranes.

D.C. Series Motors.

Cranes need high starting torque, so DC series motors are suitable.

16.List the types of electrical braking?

Dynamic Braking [ Rheostatic Braking]

Plugging

Regenerative Braking

17.State the advantages of electrical braking.

Heat produced by this braking does not affect the system.

It is smooth and cheep cost.

System capacity can be raised by applying electrical braking.

18.Why DC series motor is started with load?

It has high starting torque and high speed at No Load. So, to control the

speed in a limitation, we start DC series motor with Load.


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19.State which type of motor in used for textile mills.

In Textile mills Group drives are used. It requires constant speed and high

starting toque motor. So, Double cage Induction motors are used for this

purpose.

20.Which motor is used for paper mill?

In paper mills, the rollers in conveyer and other places are need constant

speed and relative speed to one another. So, AC synchronous motor or

Schrage Motor is used for Paper Mills.


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UNIT III : ELECTRIC TRACTION

1. State any two requirements of ideal traction system.

It has High starting torque.

Withstand of Over Load in a short duration is essential. It should have high efficiency.

Track depreciation must be in small.

Simple speed control method is adopted.

No interference of Telecommunication system.

2. List down the systems used for traction.

Steam Engine drive

Internal Combustion Engine drive Battery Electric drive

Internal Combustion Engine Electric drive

Electric drive

3. What are the advantages of battery electric drive?

Pollution free. [ There is no flu gas or smoke ]

Maintenance cost is low.

4. Write the disadvantages of diesel electric traction system.

Track modification is not necessary, so Initial cost is low.

More Load is possible over than steam engine drive.

Power loss in speed control is less.

Time taken for overhauling and maintenance is low.

More reliable and high efficiency than steam engine drive.

Train and Locomotive are combined in one unit.

Obtaining of service in any time is possible.

5. Name the two methods of supplying power to electric traction.

Conductor rail system

Over head system


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6. Name the types of collection used for current collection.

Bow Collector

Pantograph Collector

7. Write down the different system of track electrification. D.C system

Single phase low frequency AC system

Single phase high frequency AC system

Three phase AC system

Composite system

8. What are the advantages of 1 low frequency AC system?

High efficiency. Improves power factor.

Less no. of substation is enough.

9. State the other name for 1 to 3 system.

Kando System.

10.List down the advantages of 25KV, 50HZ AC system.

Light overhead catenaries Less number of Substations

Simplicity of Substation design

Less Capital cost.

Higher starting efficiency.

11.What is the use of booster transformer?

In AC traction method, the return current of Locomotive flows through Rail,

earth and reaches Substation. Due to Earth usage it will interferecommunication line. To reduce this telecommunication interference

Booster Transformer is used in Traction purpose.


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12.What are the different connections of booster transformer?

Rail connected Booster System

Booster Transformer with return Feeder.

13.Define: Free running period.The period which Train runs in a constant speed is known as Free running

period. In this period, motor takes full voltage and power from supply.

14.Name the three types of electric traction services.

Urban Services

Semi Urban Services

Main Line Services

15.Draw the speed-time curve for main line service.

16.Define crest speed.

The Maximum speed attain by a train at running time is called as Crest

Speed or Maximum Speed.

17.What is schedule speed?

It is defined as the ratio between distance between two stops and sum ofactual running time & stop time.

Distance between two stops

Schedule speed = ---------------------------------------------

Actual Running Time + Stop Time


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18.Define: tractive effort.

The Effective force required in the wheel of train tends to move is known

as Tractive effort. It is denoted as newtons.

19.Define specific energy consumption.

It is the energy consumed per ton of mass of the train per Kilometer of the

run.

Total energy consumed in Whr

Specific Energy Consumption = ---------------------------------------------------

Train Mass (Ton) X Run length (KM)

20.What are the factors that effecting specific energy consumption. Distance between stops

Acceleration and Retardation

Gradient

Train Resistance

Types of train equipment

21.Name the motors used for traction purpose.

D.C Series motor A.C Series motor

Repulsion motor

Three phase induction motor

Linear induction motor

22.Why control equipment is required?

To prevent the motor takes high current at the time of starting.

To ensure smooth acceleration without any disturbance of coupling& Travelers.

To adjust the speed depends upon the Type of service and route

condition.


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23.What are the methods used for starting a DC traction motor?

Plain Rheostatic starting

Series-Parallel starting

Metadyne control

24.What is meant by braking?

Braking is a process to stop the traction motor when it is rotate after

disconnecting the collector by means of inertia.

25.State any two requirements of braking system.

Braking system must be strong to stop the vehicle.

Easy to operate.

It should have unbreakable moving parts. It should not affect with moisture and oil.

It should be less maintenance.

It should not make any vibration or jerk on applying of brake.

26.Name the two types of braking.

Mechanical Braking

Electrical Braking

27.List down the braking system under mechanical braking.

Pneumatic Braking

Magnetic Braking

Vacuum braking

28.What are the disadvantages of regenerative braking?

Requirement of additional equipments, Capital cost is high.

In D.C traction system, size of the DC motor can be in large.


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UNIT IV : ILLUMINATION

1. What is illumination?

An amount of light energy falls in a unit area is known as illumination. It is

denoted as the Letter E and Its unit is lux.

2. Define: candle power.

It expresses levels of light intensity in terms of the light emitted by a

candle of specific size and constituents. In modern usage Candlepower

equates directly to the unit known as thecandela.

3. Define: Luminous flux.

The Luminous flux is defined as the total quantity of light per second froma luminous body. The unit is lumens.

4. Define: Solid angle.

The angle subtended at a point in space by an area is called Solid angle.

It is denoted by the symbol , and its unit is steradian.

5. What is M.S.C.P?

Mean Spherical Candle Power is the average of candle power of a source

of light in all directions in all the planes. Unit is Candela.

6. What is glare?

Glare is experienced when a source of light, in the field of view interferes

with seeing. It is classified into Direct and Indirect Glare.

7. Define: space height ratio.

The ratio of horizontal distance between lamps and mounting height of the

lamps is defined as Space Height Ratio.

8. What is the value for depreciation factor commonly used?

The value for depreciation factor commonly used is 0.8
http://en.wikipedia.org/wiki/Candlehttp://en.wikipedia.org/wiki/Candelahttp://en.wikipedia.org/wiki/Candelahttp://en.wikipedia.org/wiki/Candle


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9. Define: absorption factor and reflection factor.

The ratio between reflected light and incident light is defined as reflection

factor.

10.What are the essential qualities of a good lighting system?

It can be make required illumination.

It can be spread constant lighting over working plane.

It should not have Glare and Shadow.

It can be lighted with suitable colour of light.

It can be avoid the over contrast.

11.Define: inverse square law.The illumination of a surface is inversely proportional to the square of the

distance the source to surface.

12.Define: Lamberts cosine law.

The illumination is directly proportional to the cosine of angle between the

Normal and the lines of flux.

13.Name the resources of light?

Natural sources

Artificial sources

14.List out the electrical sources of light.

Incandescent Lamps

Arc Lamps

Gaseous discharge Lamps

15.What are the advantages of halogen lamp?

Size is small.

Lifetime is high. ( about 2000 Hrs)

Does not form Black smoke inside the lamp, so output does not

affect.


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16.Name of the classification in discharge lamp.

Sodium Vapor Lamp

Neon Lamp

High Pressure mercury vapor lamp Fluorescent Lamp

17.Define: stroboscopic effect.

The fluorescent lamp shows a small amount of flickering when it is

operated in AC supply. It has 50 times dark and 50 times bright in a

second. This flickering effect is known as Stroboscopic effect.

18.How stroboscopic effect can be avoided? Connect adjacent tube lights in various phase supply in Three phase

system.

Twin tube light fittings are used in single phase system.

19.Compare filament lamp and fluorescent lamp.

Filament lamp Fluorescent lampInitial cost is Low. Initial cost is high.

Stroboscopic effect is not possible. Stroboscopic effect is possibleLife time is short. ( about 1000 Hrs ) Life time is 5 times over than

filament lamp.Lumens output varies by means ofvoltage fluctuations.

Choke is used to absorb thevariation and output lumensmaintains nearly constant.

20.Name the types of lighting scheme?

Direct lighting

In direct lighting

Semi-direct lighting

Semi-indirect lighting

General lighting


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21.Write the illumination level required for bed room and fitting shop.

Level of illumination required for bed room is 60100 Lumens/m2

Level of illumination required for Fitting shop is 200250 Lumens/m2

22.What are the factors to be considered while designing lighting scheme?Utilization factor

Depreciation factor and Maintenance factor

Waste light factor

Spaceheight ratio

23. Where flood lighting scheme is used?

Public places and Historical places.

Garden lightings on Public park in night time.

Advertisement Boards and Publicity posters.

Railways and Car parking.

Play grounds or stadiums.


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UNIT-V : ELECTRIC HEATING AND WELDING

1. What are the advantages of electric heating?

Economically best. Efficiency is high.

Pollution free, because of absence of unwanted gas.

Easy to control.

Low maintenance cost.

Automatic Production.

2. List out the classification of heating methods based on temperature?

Low temperature heating (up to 400

0

C) Medium temperature heating ( 4000C11500C )

High temperature heating (above 11500C)

3. Name the modes of heat transfer?

Conduction

Convection

Radiation

4. Define: radiation.

In this method, heat is transferred from one to another place by means of

heat waves. It does not heat the medium in between these two places.

Heat waves heat the materials which oppose it.

5. How electric heating can be classified?

Power Frequency Heating

High Frequency Heating

6. What are the advantages of high frequency eddy current heating?

Cost is cheap.

Power loss is less.

Accurate & Automatic control is possible.


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7. List the applications of dielectric heating.

Food processing.

Wood processing.

Drying purpose in textile industry.

8. What are the requirements of heating element materials?

High resistivity.

Low temperature co-efficient of resistance.

High melting point.

Free from oxidation.

Withstand vibrations.

9. Write down the commonly used heating element materials and their

mixing rates.

Nickel Chromium alloy80% nickel and 20% chromium.

Nickel Chromium Iron alloy65% nickel, 15% chromium and 20%

iron.

10.State any two property of nickel-chromium.

Resistance value is 1.03 X 10-6ohm-m.

Melting point is 13750C

Limiting temperature is 10000C

11.Give the temperature range obtained from the arc by using white graphite

or carbon electrode.

The temperature range obtained from the arc by using white graphite or

carbon electrode is 30000C to 35000C.

12.Name the two types of arc furnace. Direct Arc Furnace

In direct Arc Furnace


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13.How can control the arc furnace?

Adjust the distance between electrodes and change the arc gap and

get the change in resistance in Arc.

Tap changing in transformer primary leads to change the voltage

across the furnace.

14.What are the advantages of coreless induction furnace?

Time to reach melting point is low.

Accurate power control can be done.

There is no smoke, unwanted gas and noise.

Capital cost is low.

15.Name the major types of electric welding. Resistance welding

Arc welding

16.What are the types of resistance welding?

Butt welding

Spot welding

Seam welding

Projection welding

Flash welding

17.What are the types of arc welding?

Carbon arc welding

Metal arc welding

Atomic hydrogen arc welding

Inert gas metal arc welding

Submerged arc welding

18.List out the requirements of good welding.

Joint surface of welded metal must be same in all places.

Width of welding is constant over the welding.

Over lap, under cut and cavities are not presented in the welded

surface.


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19.What are the electrodes used for welding?

Bare electrodes

Lightly coated electrodes

Heavily coated electrodes

20.Name the methods used for controlling welding current.

Tapped reactor method

Moving coil method

Magnetic shunt method

Saturable reactor method

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