Transmission and Distribution MCQ Quiz - Objective Question with Answer for Transmission and Distribution - Download Free PDF

Last updated on Apr 4, 2025

Latest Transmission and Distribution MCQ Objective Questions

Transmission and Distribution Question 1:

The full name of S. L. type cable is __________.

  1. straight line type cable
  2. stranded line type cable
  3. separate lead type cable
  4. selective level type cable

Answer (Detailed Solution Below)

Option 3 : separate lead type cable

Transmission and Distribution Question 1 Detailed Solution

Classification of cable based on construction

Belted cable:

  • In such cables, the conductors (usually three) are bunched together and then bound with an insulating paper ‘belt’.
  • In such cables, each conductor is insulated using paper impregnated with a suitable dielectric. The gaps between the conductors and the insulating paper belt are filled with a fibrous dielectric material such as Jute or Hessian. 
  • There are some limitations of such construction. Since the electric field is tangential, the insulation provided is stressed. As a result, the dielectric strength falls over time. Hence, such construction isn’t preferred for voltage levels above 11 kV.


Screened cable:

It is further divided as H type and S.L. type cables:

H-Type Cable:

  • H-type cables are high-voltage paper-insulated cables designed for underground power transmission. They are mainly used for voltages up to 66 kV.
  • The three cores are individually insulated with paper and then covered by a metallic screen/cover. These metallic covers are perforated. As a result, such construction allows the three metallic screens to touch each other.


S. L. Type Cable:

  • The full form of SL-type cable is Separate Lead type cable. Such construction is limited for voltages up to 66kV only.
  • SL-type cables are an improved version of H-type cables, used for underground high-voltage power transmission. They feature separate lead sheaths over each core, providing better insulation and fault protection compared to H-type cables.


Pressure cables:

  • For voltages beyond 66 kV, the electrostatic stresses in the cables exceed the acceptable values and solid cables become unreliable.
  • This occurs mainly because voids are created when voltages exceed 66 kV. Hence, instead of solid cables, we use Pressure cables.
  • Typically, such cables are either oil filled or gas filled.

Transmission and Distribution Question 2:

Which of the following layers of the underground cable consist of a fibrous material?

  1. Bedding and armouring
  2. Armouring and serving
  3. Bedding and serving
  4. Bedding, serving and armouring

Answer (Detailed Solution Below)

Option 3 : Bedding and serving

Transmission and Distribution Question 2 Detailed Solution

Construction of the underground cable

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Cores or Conductors: 

  • A cable may have one or more than one core (conductor) depending upon the type of service for which it is intended.
  • The conductors are made of tinned copper or aluminum and are usually stranded to provide flexibility to the cable.
     

Insulation

  • Each core or conductor is provided with a suitable thickness of insulation, the thickness of the layer depending upon the voltage to be withstood by the cable.
  • The commonly used materials for insulation are impregnated paper, varnished cambric, or rubber mineral compounds.
     

Metallic sheath

  • To protect the cable from moisture, gases, or other damaging liquids (acids or alkalies) in the soil and atmosphere, a metallic sheath of lead or aluminum is provided over the insulation.
     

Bedding

  • Over the metallic sheath is applied a layer of bedding which consists of a fibrous material like jute or hessian tape. The purpose of bedding is to protect the metallic sheath against corrosion and mechanical injury due to armoring.
     

Armouring

  • Over the bedding, armoring is provided which consists of one or two layers of galvanized steel wire or steel tape. Its purpose is to protect the cable from mechanical injury while laying it and during handling. 
     

Serving

  • To protect armoring from atmospheric conditions, a layer of fibrous material (like jute) similar to bedding is provided over the armoring. This is known as serving

Transmission and Distribution Question 3:

A feeder, in a transmission system, feeds power to _______ 

  1. distributors
  2. generating stations
  3. service mains
  4. All of the given options

Answer (Detailed Solution Below)

Option 1 : distributors

Transmission and Distribution Question 3 Detailed Solution

  • That part of power system which distributes electric power for local use is known as distribution system. In general, the distribution system is the electrical system between the substation fed by the Transmission system and the consumer’s meters.
  • It generally consists of feeders, distributors, and service mains.

SSC JE 29th mnng 1

  • Feeder: A feeder is a conductor which connects the sub-station (or localized generating station) to the area where power is to be distributed. Feeders feed power to distributors. Generally, no tapings are taken from the feeder so that current in it remains the same throughout. The main consideration in the design of a feeder is the current carrying capacity.
  • Distributors: A distributor is a conductor from which tapings are taken for supply to the consumers. In Fig. AB, BC, CD and DA are the distributors. The current through a distributor is not constant because tapings are taken at various places along its length. While designing a distributor, voltage drop along its length is the main consideration since the statutory limit of voltage variations is ± 6% of rated value at the consumers’ terminals.
  • Service mains: A service mains is generally a small cable which connects the distributor to the consumers’ terminals.

Transmission and Distribution Question 4:

Compared to glass insulators the mechanical strength of porcelain insulators is ______.

  1. very low
  2. the same
  3. half
  4. very high

Answer (Detailed Solution Below)

Option 4 : very high

Transmission and Distribution Question 4 Detailed Solution

The correct answer is "option 4"

Concept:

  • Porcelain is the most commonly used material for overhead insulators in the present day.
  • The porcelain is aluminum silicate. The aluminum silicate is mixed with plastic kaolin, feldspar, and quartz to obtain final hard and glazed porcelain insulator material.
  • The surface of the insulator should be glazed enough so that water should not be traced on it.
  • Porcelain also should be free from porosity since porosity is the main cause of deterioration of its dielectric property.
  • It must also be free from any impurity and air bubble inside the material which may affect the insulator properties.
  • Porcelain has a dielectric strength of 60kV/cm.

Additional Information

  • The electrical strength of glass generally remains unchanged during the entire working period, and its aging process is much slower than that of porcelain.
  • Under the effect of standard shock wave, the electrical breakdown strength of glass medium is 1350~1700 kV/cm, which is about 3.8 times that of porcelain.
  • Glass is made through a process called annealing and it has a higher dielectric strength as compared to porcelain.
  • While the resistivity of glass is very high, the coefficient of thermal expansion is low..
  • The glass insulators have higher resistant to breaking as compared to the ceramics and its mechanical compressive strength is 1.5 times higher than ceramics.
  • The electrical resistance is much higher than that of ceramic insulators (between 500 kV/cm and 1000 kV/cm).

Transmission and Distribution Question 5:

The domestic electrical appliances mostly operate at what voltage?

  1. 40 V AC
  2. 40 V DC
  3. 230 V AC
  4. 130 V DC

Answer (Detailed Solution Below)

Option 3 : 230 V AC

Transmission and Distribution Question 5 Detailed Solution

In India, household appliances generally operate on 230 V, 50 Hz single-phase supply

Country

1 - ϕ Voltage ( Volts)

Supply frequency (Hz)

Plug type

Australia

officially 230 V (in practice often 240 V)

50 Hz

I

Brazil

127 V / 220 V

60 Hz

C / N

China

220 V

50 Hz

A / C / I

France

230 V

50 Hz

C / E

India

230 V

50 Hz

C /D /M

Pakistan

230 V

50 Hz

C / D

United Kingdom (UK)

230 V

50 Hz

G

United States of America (USA)

120 V

60 Hz

A / B

Top Transmission and Distribution MCQ Objective Questions

Which among the following is the standard voltage used for primary distribution?

  1. 1 kV
  2. 8 kV
  3. 15 kV
  4. 11 kV

Answer (Detailed Solution Below)

Option 4 : 11 kV

Transmission and Distribution Question 6 Detailed Solution

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Transmission lines and distribution lines can be discriminated by their operating voltage. The voltage levels of transmission and distribution are given below.

Power carrying system

Voltage level

Primary transmission

66 kV, 132 kV, 220 kV or 400 kV

Secondary transmission

33 kV

Primary distribution

11 kV

Secondary distribution

400 V

 

Important Points:

The differences between transmission and distribution lines are given below.

Transmission line

Distribution lines

It helps in the movement of electricity from the power plant to the substations

It carries electricity from the substation to the consumer’s end

It carries electricity in three-phase supply system

It requires a single-phase supply system for carrying electricity

Carries electricity at a very high voltage

It carries electricity at a very low and safe level

These are thick lines

These are thin as compared to the transmission line

11 k V line at dead end employs, the insulator is

  1. Shackle
  2. Pin
  3. Disc
  4. None of the above

Answer (Detailed Solution Below)

Option 3 : Disc

Transmission and Distribution Question 7 Detailed Solution

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For an 11 kV line at a dead end, the type of insulator typically employed is a disc insulator. Disc insulators are commonly used in high voltage applications, especially where the line tension is considerable, as is the case at dead ends. They are designed to withstand the mechanical load and provide the necessary electrical insulation.

Therefore, the correct answer is: 3) Disc

Important Points Other options such as shackle insulators are mainly used for low-voltage distribution systems, and pin insulators are commonly used for lower voltage levels (up to 33 kV), but disc insulators are most suitable for the given scenario.

The function of steel wire in an ACSR conductor is to

  1. help carry additional current
  2. reduce the resistance of the line
  3. take up the mechanical tension in the line
  4. none of the above

Answer (Detailed Solution Below)

Option 3 : take up the mechanical tension in the line

Transmission and Distribution Question 8 Detailed Solution

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ACSR (Aluminium Conductors Steel Reinforced ) conductor:

  • It is a type of high-capacity, high-strength stranded conductor having a steel core and outer strands of aluminum.
  • It is chosen for its good conductivity, low weight, low cost, resistance to corrosion, and decent mechanical stress resistance.
  • The center strand is galvanized steel for additional strength to help support the weight of the conductor and provide additional mechanical strength.
  • Steel has higher strength than aluminum which allows for increased mechanical tension to be applied to the conductor.

Which of the following fuse wires has a sharp melting action?

  1. Bronze
  2. Copper
  3. Silver
  4. None of the above

Answer (Detailed Solution Below)

Option 3 : Silver

Transmission and Distribution Question 9 Detailed Solution

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The correct answer is option 3):  Silver

Concept:

  • A fuse is an electrical safety device that operates to provide overcurrent protection of an electrical circuit.
  • The fuse wire  will have low melting point 
  • The material used for fuse elements must have the following properties:
  1. Low melting point
  2. Low ohmic loss
  3. High conductivity (or low resistivity)
  4.  Free from detraction 
  • The materials used for fuse: The material mainly used as fuse elements are tin, lead, silver, copper, zinc, aluminium, and an alloy of lead and tin An alloy of lead and tin is used for small current rating fuses
  • Silver provides an excellent balance of mechanical strength, moderate melting and evaporation temperatures, high electrical conductivity to oxidation during prolonged operation at elevated temperatures.
  • Silver fuse elements provide stable and reliable performance under normal load conditions, predictable operation under circuit overloads, and current limiting and rapid circuit interruption under fault conditions.
  • While expulsion fuses are typically limited to interruption currents below 20 kA, HRC fuses are available to interrupt fault currents of 50 - 200 k
  • melting point of silver is 961.8 c , melting point of copper is 1085 , melting point of bronze is 913 C. Though melting bronze is minimum it will react with oxygen easily.So usage of bronze for fuse is not advisible

The current on a high voltage line is measured using:

  1. Current shunt
  2. Voltage transformer
  3. Load resistor
  4. Current transformer

Answer (Detailed Solution Below)

Option 4 : Current transformer

Transmission and Distribution Question 10 Detailed Solution

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Transformers used in conjunction with measuring instruments for measurement purposes are called instrument transformers. The actual measurements are done by the measuring instruments only.

Where the current and voltage are very high, direct measurements are not possible as these current and voltage are too large for reasonably sized instruments and the cost of the meter will be high.

The solution is to step-down the current and voltage with instrument transformers, so that, they could be metered with instruments of moderate size.

Instrument transformers are two types: potential transformer and current transformer.

The potential transformer is used to step down the high voltages and current transformers are used to step down the high currents.

For voltages higher than _________, the switchgear equipment is mounted outside.

  1. 33 kV
  2. 11 kV
  3. 66 kV
  4. 44 kV

Answer (Detailed Solution Below)

Option 3 : 66 kV

Transmission and Distribution Question 11 Detailed Solution

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Classification of a switchgear according to constructional feature:

1.) Outdoor switchgear:

  • The switchgear equipment is mounted outside for a voltage higher than 66 kV.
  •  It is because, for such voltages, the clearances between conductors and the space required for switches, circuit breakers, and other equipment become so great that it is not economical to install the equipment indoors.

2.) Indoor switchgear:

  • For voltages up to 11 kV, equipment is invariably installed inside of the substation.
  • When the atmosphere is contaminated with impurities, this switchgear can be erected for a voltage of up to 66 kV.

3.) Underground switchgear:

  • In thickly populated, the space available is less and more expensive. Under such conditions, the substation is created underground.

4.) Pole-mounted switchgear:

  • It is an outdoor substation with a pole mounted on a 4 pole structure.
  • It is the cheapest form of substation for voltage up to 11 kV.

What is the advantage of armored cable?

  1. It has higher insulation resistance
  2. It can sustain high voltage
  3. It can smoothly travel through gland
  4. It can sustain higher impact

Answer (Detailed Solution Below)

Option 4 : It can sustain higher impact

Transmission and Distribution Question 12 Detailed Solution

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  • In armored cable, Steel Wire Armour (SWA) used for higher mechanical protection. So that the cable can withstand higher stresses or impact.
  • It can be buried directly and used in external or underground projects.
  • The armored cable can withstand extreme temperature conditions up to 15000°C.
  • Using armored cables helps in insulating the transmission components from emitting the interference and also from being affected by interferences that are being emitted from neighboring cables and also appliances.

Cable lugs are also called:

  1. Cable shoes
  2. Cables ends
  3. Cables covers
  4. Cable bends

Answer (Detailed Solution Below)

Option 1 : Cable shoes

Transmission and Distribution Question 13 Detailed Solution

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  • Cable lugs are also known as Cable terminal ends or cable shoes.
  • Cable lugs in electrical supplies utilized to securely connect or terminate cables to electrical devices, power or control panels, junction boxes, equipment, and machinery. These lugs are often used to join power cables together as well.
  • Cable lugs are the devices used for connecting cables to electrical appliances, other cables, surfaces, or mechanisms.
  • The clamps that connect wires to an automotive battery, the ends of battery jumper cables are common examples of cable lugs.

F4 Vinanti Engineering 21.02.23 D6

Additional InformationThe terms cable ends and cable shoes are often used interchangeably, but they refer to different components in electrical systems. Here's the difference between the two:

  • Cable Ends :
    Definition: Cable ends refer to the exposed tips of electrical cables where the insulation has been removed to allow the wire to be connected to another device, terminal, or conductor.
    Purpose: The purpose of exposing cable ends is to create a point of electrical contact or connection, either by inserting the exposed wires into a terminal block or by attaching them to another wire or device.
    Appearance: Cable ends consist of bare wires, sometimes twisted or prepared to be inserted into terminals or connected with a connector like a lug or a shoe.
     
  • Cable Shoes(Cable Lugs) :
    Definition
    : Cable shoes, also called cable lugs, are metal connectors attached to the cable ends. These lugs are designed to securely connect cables to terminals, switches, or other electrical devices.
    Purpose: The purpose of a cable shoe is to provide a stable and secure connection between the cable and the electrical device. Cable shoes ensure a firm and reliable connection, reducing the risk of loose connections or arcing.
    Appearance: Cable shoes are metal pieces with a hole at one end (for bolting or screwing) and a barrel at the other end where the exposed cable wire is inserted and crimped.

    Key differences
  • Cable ends are simply the exposed ends of wires, whereas cable shoes are metal fittings or connectors that are attached to the cable ends to make secure electrical connections.
  • Cable ends need to be connected directly to terminals, while cable shoes offer a more permanent and durable solution, allowing the cables to be bolted or screwed into place.

    Summary : Both components are part of electrical connections, but cable shoes enhance the functionality of cable ends by ensuring secure and reliable attachments.
  • Cable Ends: Exposed tips of wires.
  • Cable Shoes: Metal connectors (lugs) attached to cable ends for secure electrical connections.

Which among the below is not generally used for distribution systems?

  1. 1 phase, 3 wire system
  2. 3 phase, 3 wire system
  3. 3 phase, 4 wire system
  4. 1 phase, 4 wire system

Answer (Detailed Solution Below)

Option 4 : 1 phase, 4 wire system

Transmission and Distribution Question 14 Detailed Solution

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Primary transmission :

The electric supply (132 kV, 220 kV, 500 kV or greater) is transmitted to load center by three-phase three-wire (3 phase - 3 wires) overhead transmission system.

Secondary transmission :

At the receiving station, the level of voltage reduced by step-down transformers up to 132 kV, 66 or 33 kV and electric power is transmitted by three-phase three-wire (3 phase - 3 wires) overhead system to different substations.

Primary distribution :

At a substation, the level of secondary transmission voltage (132KV, 66 or 33KV) is reduced to 11 kV (in a three-phase three-wire overhead system) by step down transformers.

Secondary distribution :

  • Electric power is given to (from primary distribution line (i.e.) 11 kV) distribution substation.
  • This substation is located nearby consumers area where the level of voltage reduced by step down transformers is 415 V.
  • In a 3 phase four wire system (3 phase - 4 wires), there are 415 volts (Three-phase supply system) between any two phases and 230 volts (single-phase supply) between neutral and any one of the phases (lives) wire.
  • Residential load (i.e. Fans, light, and TV, etc) may be connected between any one phase and neutral wires, while three-phase loads may be connected directly to the three-phase lines.
  • A three-phase 415V, supply is used for supplying small industrial and commercial loads such as garages, schools, and blocks of flats. A single-phase 230 V supply is usually provided for individual domestic consumers.

Which of the following is called a service main? 

  1. Conductor connecting generating station to substation 
  2. Conductor connecting consumer’s terminal to the distributor 
  3. Conductor connecting substation to substation 
  4. Conductor connecting consumer’s terminal to the distribution substation

Answer (Detailed Solution Below)

Option 2 : Conductor connecting consumer’s terminal to the distributor 

Transmission and Distribution Question 15 Detailed Solution

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The correct answer is option 2):(Conductor connecting consumer’s terminal to the distributor )

Concept:

Service Mains:

  • The conductor connecting the consumer’s terminals to the distributor is called the service main
  • Service mains of the consumers may be either connected to the distributors or sub-distributors

F2 Vinanti Engineering 12.01.23 D8

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