Power System Protection MCQs Part 9

a. The bushing is used with power equipment to:

  1. Prevent contact between the conductor and metal equipment
  2. To facilitate the current flow between conductor and chassis ground
  3. Increase the life of the equipment
  4. None of these

Correct answer: 1. Prevent contact between the conductor and metal equipment

b. Instrument transformers are used:

  1. To Protect the electrical equipment
  2. To isolate the relays
  3. To isolate ammeter and multimeters
  4. All of these

Correct answer: 4. All of these

c. The correct statement about arc resistance:

  1. It increases with the length of the arc
  2. It decreases with the length of the arc
  3. Length and resistance of arc are never related
  4. None of above

Correct answer: 1. It increases with the length of the arc

d. The breaking capacity of the circuit breaker is:

  1. R.M.S
  2. Peak
  3. Both
  4. None

Correct answer: 1. R.M.S

e. The circuit breaker which is recommended for EHV Installations:

  1. Low oil breaker
  2. Bulk oil circuit breakers
  3. SF6 circuit breaker
  4. Air blast circuit breaker

Correct answer: 3. SF6 circuit breaker

f. The air which is preferred for air blast circuit breakers:

  1. Moisture free air
  2. Air with 50% nitrogen
  3. Air with 25% hydrogen
  4. Air with higher moisture content

Correct answer: 1. Moisture free air

g. The natural frequency of a 60 Hz generator having inductance  10 mH and capacitance 50 µF has a natural frequency of:

  1. 2 Hz
  2. 60 Hz
  3. 225 Hz
  4. 22500 Hz

Correct answer: 3. 225 Hz

Solution: f = 1/2π √10 m * 50 u = 225 Hz

h. Low resistance method of arc extinction is also known as:

  1. High current method
  2. Low current method
  3. Current zero method
  4. Current infinite method

Correct answer: 3. Current zero method

i.  ________________ relays are used in large-sized alternator for providing protection against overloads:

  1. Temperature sensitive
  2. Overcurrent
  3. Impedance
  4. Induction relays

Correct answer: 1. Temperature relays

j. The arc in circuit breaker converts oil into:

  1. Fire
  2. Hydrogen gas
  3. SF6 Gas
  4. Nitrogen gas

Correct answer: 2. Hydrogen gas

Continue reading:

Leave a Reply