Testing And Commissioning Of Electrical Equipment’S Set 8

Electrical Engineering

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This set of Testing and Commissioning of Electrical Equipment’s Multiple Choice Questions & Answers (MCQs) focuses on Testing And Commissioning Of Electrical Equipment’S Set 8

Q1 | The heat produced at the contact point owing to flow of electric current is leastaffected by_____________________.
  • Temperature of the surrounding medium.
  • Contact resistance.
  • Magnitude of electric current flowing.
  • Duration of flow of current.
Answer: Temperature of the surrounding medium.
Q2 | The resistance of an electric arc can be increased by
  • Increasing the concentration of ionised particles.
  • Reducing the arc length.
  • Splitting the ar(C)
  • Increasing the arc cross section.
Answer: Splitting the ar(C)
Q3 | By using low resistance method for arc extension what is the value of arcresistance?
  • Arc resistance is zero.
  • Arc resistance is high
  • Arc resistance is low
  • Arc resistance is very high
Answer: Arc resistance is low
Q4 | What happens in the arc extinction using high resistance method?
  • Arc resistance is decreased with time.
  • Arc resistance is increased with time.
  • No change it remains same.
  • Arc resistance is kept zero.
Answer: Arc resistance is increased with time.
Q5 | What is the arc voltage in a circuit breaker?
  • In phase with the arc current.
  • Lagging the arc current by 90°
  • Leading the arc current by 90°
  • Lagging the arcing current by 180°
Answer: In phase with the arc current.
Q6 | Arcing voltage will be the least in case of
  • Carbon
  • Copper
  • Silver
  • Tungsten
Answer: Silver
Q7 | How is the initiation of electric arc at the instant of contact separation caused?
  • Thermionic emission of electrons.
  • Field emission of electrons.
  • Both (a) and (b)
  • None of these.
Answer: Both (a) and (b)
Q8 | The arc resistance depends on which among the following factors?
  • Cross section of the ar(C)
  • Length of the ar(C)
  • Degree of ionization
  • All of the above.
Answer: All of the above.
Q9 | Which type of tripping is generally preferred for the circuit breaker?
  • Manual
  • Automatically
  • Depending on the voltage level
  • None of the above
Answer: Automatically
Q10 | Which part of the circuit breaker is helpful in breaking the current?
  • Trip coil.
  • Contacts.
  • Medium
  • Handle.
Answer: Contacts.
Q11 | When a fault occurs in a high voltage transmission line, what happens first?
  • Circuit breaker operates then the relay.
  • Relay operates and then the circuit breaker.
  • Relay operates, then successively the isolator and the circuit breaker.
  • Isolator operates, then successively the relay and the circuit breaker.
Answer: Relay operates and then the circuit breaker.
Q12 | Upto what voltage can the liquid type HRC fuses be used?
  • 33 kV
  • 132 kV
  • 66 kV
  • 220 kV
Answer: 132 kV
Q13 | What is the main advantage of using a fuse?
  • Cheapest type of protection.
  • Inverse time current characteristics.
  • Current limiting effect under short circuit conditions.
  • All of above.
Answer: All of above.
Q14 | On what basis is the selection of fuse done?
  • Steady loa(D)
  • Fluctuating loa(D)
  • Both (a) and (b)
  • None of these.
Answer: Both (a) and (b)
Q15 | Upto what voltage a cartridge type of fuse can be used?
  • 400 V
  • 11 kV
  • 20 kV
  • 33 kV
Answer: 33 kV
Q16 | In a HRC fuse what is the time between the cut off and the final current zerocalled?
  • Pre - arcing time.
  • Arcing time.
  • Total operating time.
  • None of these.
Answer: Arcing time.
Q17 | Which material is used in the liquid type of fuse?
  • SF6
  • Distilled water
  • Carbon tetra chloride.
  • Mineral oil / transformer oil
Answer: Carbon tetra chloride.
Q18 | What is the advantage of HRC fuses over Rewirable fuses?
  • High speed operation
  • High rupturing capacity
  • No ageing effect.
  • All of the above.
Answer: All of the above.
Q19 | If the strands of the fusing wire are twisted, what happens to the fusing current?
  • Increases
  • Reduces.
  • No change/ remains same
  • Depends on the value of current, increases or decreases.
Answer: Reduces.
Q20 | What is the typical value of the pre arcing time?
  • 0.1
  • 0.01
  • 0.001
  • 0.0001
Answer: 0.001
Q21 | Outdoor switchgear is generally used for voltage beyond
  • 11 KV
  • 33 KV
  • 66 KV
  • 132 KV
Answer: 66 KV
Q22 | The least expensive protection for over current in low-voltage system is
  • Rewirable fuse
  • Isolator
  • Circuit breaker
  • Air-break switch
Answer: Rewirable fuse
Q23 | Purpose of backup protection is
  • To increase the speed
  • To increase a reach
  • To leave no blind spot
  • To guard against failure of primary
Answer: To guard against failure of primary
Q24 | We do not require any protection against prime mover failure in case of
  • Turbo generator sets
  • Hydro generator sets
  • Diesel engine driven alternators
  • Back pressure turbo generators
Answer: Turbo generator sets
Q25 | For the protection of stator winding of an alternate against internal fault involvingground the relay used is a
  • Biased differential relay
  • Directional over-current relay
  • Plain impedance relay
  • Buchholz relay
Answer: Biased differential relay
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