Testing And Commissioning Of Electrical Equipment’S Set 5 MCQs

Q1 | What is the actuating quantity for the relays?

Magnitude

Frequency

Phase angle

All of these

Q2 | Which among these are the main characteristics of a fuse element?

Low melting point

High conductivity

Least deterioration due to oxidation

All of the above

Q3 | What is the making capacity of the circuit breaker?

Less than the asymmetrical breaking capacity of the breaker

Greater than the asymmetrical breaking capacity of the breaker

Equal to the asymmetrical breaking capacity of the breaker

Equal to the symmetrical breaking capacity of the breaker

Q4 | In a circuit breaker the contact space is ionised by what?

Field emission from the contact surface.

Thermal emission from the contact surface.

Thermal ionisation of gas.

All of above.

Q5 | A three phase, 33 kV oil circuit breaker is rated 1200 A, 2000 MVA, 3s. What isits symmetrical breaking current?

1200 A

3600 A

35 kA

104.8 kA

Q6 | What should be the value of fusing factor?

Equal to zero

Equal to one

Less than one

More than one

Q7 | What is the relation between the fusing current and the diameter of the wire?

I = k d3

I = k d3/2

I = k d2

I = k d2/3

Q8 | The making and breaking currents of a 3 phase ac circuit breakers in powersystems are respectively in ________form.

rms value, rms value

instantaneous value, rms value

rms value, instantaneous value

instantaneous value, instantaneous value

Q9 | Why is an isolator installed?

To isolate one portion of the circuit from another

As an substitute for the circuit breaker

It used on either sides of the circuit breaker

Both (a) and (c)

Q10 | Assertion (A): In comparison to making capacity of a circuit breaker its breakingcapacity is normally higher. Reason (R): The breaking capacity of a CB is expressed as ?3 * VI * 10-6 MVA

Both A and R are true and R is the correct explanation of A

Both A and R are true and R is not the explanation of A

A is true but R is false

A is false but R is true.

Q11 | What is the cut off current in the fuse?

Maximum value actually reache(D)

Rms value actually reache(D)

Average value actually reach

Q12 | Which circuit breaker is preferred to be installed in extra high voltage ACsystem?

Bulk oil type circuit breaker

Air blast circuit breaker

SF6 circuit breaker

Vacuum circuit breaker

Q13 | A three phase circuit breaker is rated 2000 MVA, 33 kV. What will be its makingcurrent?

35 kA

49 kA

70 kA

89 kA

Q14 | 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?

0.2 mm

0.18 mm

0.28 mm

0.3 mm

Q15 | Which among these tests are performed to check the nation or internationalstandards?

Type test.

Production tests.

Site checks.

All of the above.

Q16 | 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?

10000 Hz

12500 Hz

12628 Hz

13265 Hz

Q17 | What is switchgear?

An apparatus used for switching, controlling and protecting the electrical circuits and equipments.

It detects the faults only.

It corrects the faults only.

All of the above.

Q18 | What is / are the main disadvantage / s of using oil as the quenching medium in the circuit breakers?

Need periodical replacement.

Risk of formation of explosive mixture with air.

Possibility of causing fire hazards.

All of the above.

Q19 | Which of the following circuit breakers has the lowest operating voltage?

SF6 circuit breaker

Air break

Air blast

Minimum oil circuit breaker

Q20 | The most efficient torque producing actuating structure for the induction typerelays is

Shaded pole structure

Watt hour meter structure

Induction cup structure

Single induction loop structure

Q21 | Plug setting of a electromagnetic relay can be altered by varying

Number of ampere turns

Air gap of magnetic path

Adjustable back stop

None of these

Q22 | Which material is used for the manufacture of bus bars?

Aluminium rods.

Copper rods.

Any conducting material.

Made of silver.

Q23 | Which device sends the information to the circuit breaker to interrupt the circuitin case of fault?

Switch

Relay

Circuit breaker itself does this function.

Fuse.

Q24 | When does the circuit breaker operate in the line?

When power is to be supplie(D)

When the line is to be teste(D)

Whenever the fault occurs in the line.

Whenever the switch and the relay has to be operate(D)

Q25 | What is the primary principle of a fuse?

Open the circuit.

Protect the appliance.

Protect the line.

Prevent excess current from flowing into the line.