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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.