Deck 9: Electrical Components and Circuit Breakers

Question 1

What is the actuating quantity for the relays?

A)Magnitude
B)Frequency
C)Phase angle
D)All of these

Answer 1

All of these

Question 2

Which among these are the main characteristics of a fuse element?

A)Low melting point
B)High conductivity
C)Least deterioration due to oxidation
D)All of the above

Answer 2

All of the above

Question 3

What is the making capacity of the circuit breaker?

A)Less than the asymmetrical breaking capacity of the breaker
B)Greater than the asymmetrical breaking capacity of the breaker
C)Equal to the asymmetrical breaking capacity of the breaker
D)Equal to the symmetrical breaking capacity of the breaker

Answer 3

Greater than the asymmetrical breaking capacity of the breaker

Question 4

In a circuit breaker the contact space is ionised by what?

A)Field emission from the contact surface.
B)Thermal emission from the contact surface.
C)Thermal ionisation of gas.
D)All of above.

Question 5

A three phase, 33 kV oil circuit breaker is rated 1200 A, 2000 MVA, 3s. What is its symmetrical breaking current?

A)1200 A
B)3600 A
C)35 kA
D)104.8 kA

Question 6

What should be the value of fusing factor?

A)Equal to zero
B)Equal to one
C)Less than one
D)More than one

Question 7

What is the relation between the fusing current and the diameter of the wire?

A)I = k d3
B)I = k d3/2
C)I = k d2
D)I = k d2/3

Question 8

The making and breaking currents of a 3 phase ac circuit breakers in power systems are respectively in ________form.

A)rms value, rms value
B)instantaneous value, rms value
C)rms value, instantaneous value
D)instantaneous value, instantaneous value

Question 9

Why is an isolator installed?

A)To isolate one portion of the circuit from another
B)As an substitute for the circuit breaker
C)It used on either sides of the circuit breaker
D)Both (a) and (c)

Question 10

What is the cut off current in the fuse?

A)Maximum value actually reache(D)
B)Rms value actually reache(D)
C)Average value actually reach

Question 11

Which circuit breaker is preferred to be installed in extra high voltage AC system?

A)Bulk oil type circuit breaker
B)Air blast circuit breaker
C)SF6 circuit breaker
D)Vacuum circuit breaker

Question 12

A three phase circuit breaker is rated 2000 MVA, 33 kV. What will be its making current?

A)35 kA
B)49 kA
C)70 kA
D)89 kA

Question 13

A fuse wire of circular cross section has a radius of 0.8mm. The wire blows off at a current of 9(A) What will be the radius of the wire that will blow off at a current of 1A?

A)0.2 mm
B)0.18 mm
C)0.28 mm
D)0.3 mm

Question 14

Which among these tests are performed to check the nation or international standards?

A)Type test.
B)Production tests.
C)Site checks.
D)All of the above.

Question 15

Refer to the following facts to answer the question A 50 Hz, 11 kV, 3 phase alternator with earthed neutral having a reactance of 3 ohms per phase and is connected to a bus bar through a circuit breaker, if the distributed capacitance upto CB between the phase and neutral is 0.01 ? F. What is the frequency of oscillations?

A)10000 Hz
B)12500 Hz
C)12628 Hz
D)13265 Hz

Question 16

What is switchgear?

A)An apparatus used for switching, controlling and protecting the electrical circuits and equipments.
B)It detects the faults only.
C)It corrects the faults only.
D)All of the above.

Question 17

What is / are the main disadvantage / s of using oil as the quenching medium in the circuit breakers?

A)Need periodical replacement.
B)Risk of formation of explosive mixture with air.
C)Possibility of causing fire hazards.
D)All of the above.

Question 18

Which of the following circuit breakers has the lowest operating voltage?

A)SF6 circuit breaker
B)Air break
C)Air blast
D)Minimum oil circuit breaker

Question 19

The most efficient torque producing actuating structure for the induction type relays is

A)Shaded pole structure
B)Watt hour meter structure
C)Induction cup structure
D)Single induction loop structure

Question 20

Plug setting of a electromagnetic relay can be altered by varying

A)Number of ampere turns
B)Air gap of magnetic path
C)Adjustable back stop
D)None of these

Question 21

Which material is used for the manufacture of bus bars?

A)Aluminium rods.
B)Copper rods.
C)Any conducting material.
D)Made of silver.

Question 22

Which device sends the information to the circuit breaker to interrupt the circuit in case of fault?

A)Switch
B)Relay
C)Circuit breaker itself does this function.
D)Fuse.

Question 23

When does the circuit breaker operate in the line?

A)When power is to be supplie(D)
B)When the line is to be teste(D)
C)Whenever the fault occurs in the line.
D)Whenever the switch and the relay has to be operate(D)

Question 24

What is the primary principle of a fuse?

A)Open the circuit.
B)Protect the appliance.
C)Protect the line.
D)Prevent excess current from flowing into the line.