Power System Protection MCQ

Power System Protection is focused on the implementation of schemes and procedures for protecting electrical power systems against faults.

The most dangerous fault

The most dangerous fault:

  1. 3 phase fault
  2. Line to line fault
  3. Line to ground gault
  4. Double line to ground fault

Correct answer: 1. 3 phase fault


Heavy current fuses have wires that are in diameter than smaller ones

Heavy current fuses have wires that are _________ in diameter than smaller ones:

  1. Larger
  2. Smaller
  3. Same
  4. Any of above

Correct answer: 1. Larger


The pickup current of a relay having 125% current setting connected to 100/5 transformer is

The pickup current of a relay having 125% current setting connected to 100/5 transformer is:

  1. 1 Amp
  2. 5 Amp
  3. 6.25 Amp
  4. 10 Amp

Correct answer: 3. 6.25 Amp


Which device signals the circuit breaker in case of fault

______________ signals circuit breaker in case of fault:

  1. Fuse
  2. Isolator
  3. CT
  4. Relay

Correct answer: 4. Relay


Buchholz relay is used for protection of

Buchholz relay is used for protection of:

  1. Busbar
  2. Transformer
  3. Alternator
  4. Motors

Correct answer: 2. Transformer

While short-circuit test on circuit breaker a protection engineer obtained following readings on single frequency transient

While short-circuit test on circuit breaker a protection engineer obtained following readings on single frequency transient:

Time to reach the peak re-striking voltage = 50 µsec

Peak re-striking voltage = 150 kV

The average RRRV is:

  1. 2.5 kV/µsec
  2. 5 kV/µsec
  3. 10 kV/µsec
  4. 50 kV/µsec

Correct answer: 5 kV/µsec

Formula Hint: Average RRRV = Peak restriking voltage/Time to reach peak value

What is the approximate value of the contact resistance of circuit breaker

What is approximate value of the contact resistance of circuit breaker:

  1. 25 µΩ
  2. 25 mΩ
  3. 25 Ω
  4. 250 Ω

Correct answer: 1. 25 µΩ

Important Note: Contact resistance test of circuit breaker may not be the sole predictor of breaker thermal performance.

Which of the following voltage surge is more harmful: 1/50 µs or 4/50 µs

Which of the following voltage surge is more harmful: 1/50 µs or 4/50 µs:

  1. 1/50 µs is more harmful
  2. 4/50 µs is more harmful
  3. Both are equally armful
  4. Insufficient data provided

Correct answer: 1. 1/50 µs is more harmful

Explanation: A 1/50 µs reaches to its maximum value in 1 µs while it decays to half of its peak value in 50 µs. While a 4/50 µs surge will reach to the maximum value in 4 µs while decays to half of its peak value in 50 µs.

More MCQ Questions

  1. Power System Protection MCQ Part 1
  2. Power System Protection MCQ Part 2
  3. Power System Protection MCQ Part 3
  4. Power System Protection MCQ Part 4
  5. Power System Protection MCQ Part 5
  6. Power System Protection MCQ Part 6
  7. Power System Protection MCQ Part 7
  8. Power System Protection MCQ Part 8
  9. Power System Protection MCQ Part 9
  10. Power System Protection MCQ Part 10

More MCQ on Power System Protection:

  1. Breaking capacity is the value
  2. Lubrication oil failure results in
  3. Which one of the following is classified as an electrical fault
  4. The most common cause of motor damage is
  5. Active fault refers to
  6. The term Passive faults in Power system refers to
  7. Incipient faults are best defined as faults that
  8. The more accurately the fault is detected by the protection system, the more is it
  9. The smaller the current a protection system detects, the more the is it
  10. Which type of fault has the highest probability of occurrence on the power system
  11. The Zero-sequence current can flow from a line to the transformer bank if the windings are in

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