Switchgear and Protection MCQs Part 11

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Switchgear and Protection MCQs Part 11

Which of the below mentioned fault imposes severest duty on circuit breaker

Which of the below mentioned fault imposes severest duty on circuit breaker:

  1. Line to Ground fault
  2. Line to Line fault
  3. Line to Line to Line fault
  4. Three phase fault

Correct answer: 4. Three phase fault

Certain power system has capacitance and inductance values 0.01 µF and 1 H

Certain power system has capacitance and inductance values 0.01 µF and 1 H. The instantaneous value of current to be interrupted is 10 A. What is the value of voltage appearing across contacts of circuit breaker:

  1. 10 kV
  2. 100 kV
  3. 10000 kV
  4. None of these

Correct answer: 2. 100 kV

Explanation:

Voltage across CB, v = i√(L/C)

v = 10 √(1 / 0.01 * 10^-6) = 100000 V = 100 kV

The fuse normally protects the system against

The fuse normally protects the system against:

  1. Lightening surges
  2. Over-current
  3. Under-current
  4. Resonance

Correct answer: 2. Over-current

The making current of a circuit breaker is generally specified in terms of

The making current of a circuit breaker is generally specified in terms of:

  1. Peak value
  2. Average value
  3. RMS value
  4. None of these

Correct answer: 1. Peak value

Capacitive circuit breaking results in

Capacitive circuit breaking results in:

  1. Open circuit
  2. Short circuit
  3. Voltage surge
  4. None of these

Correct answer: 3. Voltage surge

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