Switch Gear And Protection Set 6

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This set of Switch Gear and Protection Multiple Choice Questions & Answers (MCQs) focuses on Switch Gear And Protection Set 6

Q1 | Which component ensures the safety of the line from damage?
  • Relay
  • Circuit breaker
  • Bus bar
  • Current tr
Q2 | The tripping circuit is_
  • AC
  • DC
  • either AC or DC
  • None of these
Q3 | 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
Q4 | the most efficient torque producing actuating structure for theinduction type relays is
  • Shaded pole structure
  • Watt hour meter structure
  • Induction cup structure
  • Single induction loop structure
Q5 | If the power factor is zero, the active recovery voltage will be
  • minimum
  • 0.5
  • 0.707
  • Maximum.
Q6 | Which of the following is not a part of the circuit breaker?
  • Explosion pot
  • Fixed and moving contacts
  • Conservator
  • Operating mechanism.
Q7 | Which of the following circuit breaker will produce the least arc energy?
  • Minimum oil circuit breaker
  • Air blast circuit breaker
  • Plain oil circuit breaker
  • All will produce same energy.
Q8 | For a circuit breaker 'break time' is
  • Same as opening time
  • Opening time + arc duration
  • Opening time + arc duration + resistor current duration.
  • none
Q9 | The breaking capacity of a circuit breaker in MVA (3 phase) is given by
  • Rated service voltage x rated symmetrical current
  • 1.1 x rated service voltage x rated symmetrical current
  • (2)1/2 x rated service voltage x rated symmetrical current
  • (3)1/2x rated service voltage x rated symmetrical current.
Q10 | Which relay is used for feeders?
  • MHO relay
  • Translay relay
  • Merz price protection
  • Buchholz relay.
Q11 | Which of the following relays is used on transformers?
  • Buchholz relay
  • MHO relay
  • Merz price relay
  • None of the above.
Q12 | MHO relay is used for
  • Rectifiers
  • Circuit breakers
  • Transmission lines
  • Feeders.
Q13 | Merz-price protection is used on
  • Substations
  • Capacitor bank
  • Induction motor
  • Generators.
Q14 | The values of fault current depend on
  • Voltage at the faulty point
  • Total impedance up to the fault
  • Both (A) and (B) above
  • None of the above
Q15 | The advantage of neutral earthling is
  • Simplified design of earth fault protection
  • Over-voltages due to lightning can be discharged to the earth
  • Freedom from persistent arcing grounds
  • all of the above.
Q16 | The over-voltage surges in power systems may be caused by
  • Lightning
  • Switching
  • Resonance
  • Any of the above.
Q17 | The protection against over-voltage due to lightening is provided by
  • Use of surge diverters
  • Low tower footing resistance
  • Use of overhead ground wires
  • Any of the above.
Q18 | Which of the following is a conducting medium for electric current ?
  • Low temperature gas
  • High temperature gas
  • Dissociated gas
  • Plasma.
Q19 | In circuit-breakers the contact space is ionized by
  • Thermal ionization of gas
  • Thermal emission from surface of contacts
  • Field emission from the surface of contacts
  • Any of the above.
Q20 | Which of the following are air-break switching devices ?
  • Isolator
  • Limit switch
  • Earthling switch
  • All of the above.
Q21 | Which of the following statement about SF6 gas is incorrect?
  • It is non-toxic gas
  • It is non-inflammable
  • It has density 5 times that of air at 200C
  • It has dark yellow color.
Q22 | SF6 gas is transported in
  • Gas cylinders
  • Liquid form in cylinders
  • Solid form in boxes
  • Air cylinders.
Q23 | duringarc extinction SF6 gas
  • Decomposes into S and F ions
  • Decomposes into SF4and SF2
  • Gets oxidized
  • Reduces to SF3.
Q24 | Dielectric strength of SF6 is
  • less than that of air at atmospheric pressure
  • less than that of oil used in OCB
  • more than that of oil used in OCB
  • More at lower pressure and low at higher pressures.
Q25 | Which of the following is the demerit of SF6 circuit breakers?
  • Sealing problem of gas
  • In flux of moisture in the gas system is dangerous
  • Deterioration of quality of circuit breaker affects reliability of circuit breaker
  • All of the above.