Switch Gear And Protection Set 2

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This set of Switch Gear and Protection Multiple Choice Questions & Answers (MCQs) focuses on Switch Gear And Protection Set 2

Q1 | A transmission line is protected by
  • inrush protection
  • distance protection
  • time graded and current graded over current protection
  • both (b) and (c)
Q2 | Large internal faults are protected by
  • merz price percentage differential protection
  • mho and ohm relays
  • horn gaps and temperature relays
  • earth fault and positive sequence relays
Q3 | When a transmission line is energized, the wave that propagates on itis
  • current wave only
  • voltage wave only
  • both (a) and (b)
  • power factor wave only
Q4 | Protective relays are devices that detect abnormal conditions inelectrical circuits by measuring
  • current during abnormal condition
  • voltage during abnormal condition
  • constantly the electrical quantities which differ during normal and abnormal conditions
  • none of the above
Q5 | The voltage appearing across the contacts after opening of the circuit breaker is called______voltage.
  • recovery
  • surge
  • operating
  • arc
Q6 | Ionization in circuit breaker is facilitated by
  • high temperature
  • increase of mean free path
  • increasing field strength
  • all of the above
Q7 | In a circuit breaker the basic problem is to
  • maintain the arc
  • extinguish the arc
  • transmit large power
  • emit the ionizing electrons
Q8 | Overheating of relay contacts or contact born out is due to
  • slow making and breaking of load circuit contacts
  • foreign matter on the contact surface
  • too low contact pressure
  • all of the above
Q9 | Interruption of large currents by relay requires
  • arc suppressing blow out coils
  • wide separation of the opened contacts
  • high speed opening of contacts
  • all of the above
Q10 | Shunt capacitance is neglected while considering
  • short transmission line
  • medium transmission line
  • long transmission line
  • medium and long tr
Q11 | The arc voltage produced in A.C. circuit breaker is always
  • in phase with the arc current
  • lagging the arc current by 90?
  • leading the arc current by 90°
  • none of the above
Q12 | The time of closing the cycle, in modern circuit breakers is
  • 0.003 sec
  • 0.001 sec
  • 0.01 sec
  • 0.10 sec
Q13 | Insulation resistance of high voltage circuit breakers is more than
  • 1 mega ohms
  • 10 mega ohms
  • 100 mega ohms
  • 500 mega ohms
Q14 | H.R.C. fuses provide best protection against
  • overload
  • reverse current
  • open-circuits
  • short-circuits
Q15 | The ground wire should not be smaller than No ______ copper.
  • 2
  • 4
  • 6
  • 10
Q16 | The delay fuses are used for the protection of ________ .
  • motors
  • power outlet circuits
  • fluorescent lamps
  • light circuits
Q17 | Which of the following is the least expensive protection for overcurrent is low voltage system ?
  • Rewireable fuse
  • Isolator
  • Oil circuit breaker
  • Air break circuit breaker
Q18 | Resistance grounding is used for voltage between
  • 33kVto66kV
  • HkVto33kV
  • 3.3kVandllkV
  • none of the above
Q19 | The contacts of high voltage switches used in power system are submerged in oil. The main purpose of the oil is to
  • lubricate the contacts
  • insulate the contacts from switch body
  • extinguish the arc
  • all of the above
Q20 | In Railway applications ______ circuit breaker is used.
  • SFe
  • bulk oil
  • minimum oil
  • air break
Q21 | To protect most of the electrical equipment handling low power, thetypes of relays used are
  • thermocouple
  • electronic and bimetallic
  • both (a) and (b)
  • none of the above
Q22 | Wave trap is used to trap waves of
  • power frequencies
  • higher frequencies entering generator or transformer units
  • either of the above
  • none of the above
Q23 | Ungrounded neutral transmission system is not recommendedbecause of system
  • insulation being overstressed due to over voltages
  • insulation overstress may lead to failure and subsequent phase to phase faults
  • being inadequately protected against ground fault
  • all of the above
Q24 | The reflection co-efficient at the open circuited end of a transmissionline.
  • zero
  • infinity
  • unity
  • none of the above
Q25 | For the protection of power station buildings against direct strokes the requirements are
  • interception
  • interception and conduction
  • interception, conduction and dissipation
  • interception, conduction, dissipation and reflection