Switch Gear And Protection Set 1

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This set of Switch Gear and Protection Multiple Choice Questions & Answers (MCQs) focuses on Switch Gear And Protection Set 1

Q1 | The main function of a fuse is to
  • protect the line
  • open the circuit
  • protect the appliance
  • prevent excessive currents
Q2 | On which of the following routine tests are conducted?
  • Oil circuit breakers
  • Air blast circuit breakers
  • Minimum oil circuit breakers
  • All of the above
Q3 | SF6 gas
  • is yellow in colour
  • is lighter than air
  • is nontoxic
  • has pungent small
Q4 | The arcing contacts in a circuit breaker are made of
  • copper tungsten alloy
  • porcelain
  • electrolytic copper
  • aluminium alloy
Q5 | Which of the following medium is employed for extinction of arc in aircircuit breaker ?
  • Water
  • Oil
  • Air
  • SF6
Q6 | With which of the following, a circuit breaker must be equipped for remote operation ?
  • Inverse time trip
  • Time-delay trip
  • Shunt trip
  • None of the above
Q7 | Fault diverters are basically
  • fuses
  • relays
  • fast switches
  • circuit breakers
Q8 | A thermal protection switch can protect against
  • short-circuit
  • temperature
  • overload
  • over voltage
Q9 | Arc in a circuit behaves as
  • a capackive reactance
  • an inductive reactance
  • a resistance increasing with voltage rise across the arc
  • a resistance decreasing with voltage rise across the arc
Q10 | Thermal circuit breaker has
  • delayed trip action
  • instantaneous trip action
  • both of the above
  • none of the above
Q11 | Relays can be designed to respond to changes in
  • resistance, reactance or impedance
  • voltage and current
  • light intensity
  • all above
Q12 | Overload relays are of…… type.
  • induction
  • solid state
  • thermal
  • all above
Q13 | Thermal overload relays are used to protect the motor against overcurrent due to
  • short-circuits
  • heavy loads
  • grounds
  • all of the above
Q14 | Magnetic circuit breaker has ______ trip action.
  • delayed
  • instantaneous
  • both of the above
  • none of the above
Q15 | D.C. shunt relays are made of
  • few turns of thin wire
  • few turns of thick wire
  • many turns of thin wire
  • many turns of thick wire
Q16 | The relay operating speed depends upon
  • the spring tension
  • the rate of flux built up
  • armature core air gap
  • all of the above
Q17 | In order that current should flow without causing excessive heating orvoltage drop, the relay contacts should
  • have low contact resistance
  • be clean and smooth
  • be of sufficient size and proper shape
  • have all above properties
Q18 | Circuit breakers usually operate under
  • transient state of short-circuit current
  • sub-transient state of short-circuit current
  • steady state of short-circuit current
  • after D.C. component has ceased
Q19 | Circuit breakers are essentially
  • current carrying contacts called electrodes
  • arc extinguishers
  • circuits to break the system
  • tr
Q20 | The current zero interruption, in oil and air blast circuit breakers, is achieved by
  • lengthening of the gap
  • cooling and blast effect
  • both (a) and (b)
  • deionizing the oil with forced air
Q21 | Air blast circuit breaker is used for
  • over currents
  • short duty
  • intermittant duty
  • repeated duty
Q22 | An efficient and a well designed protective relaying should have
  • good selectivity and reliability
  • economy and simplicity
  • high speed and selectivity
  • all of the above
Q23 | Burden of a protective relay is the power
  • required to operate the circuit breaker
  • absorbed by the circuit of relay
  • developed by the relay circuit
  • none of the above
Q24 | Directional relays are based on flow of
  • power
  • current
  • voltage wave
  • all of the above
Q25 | A differential relay measures the vector difference between
  • two currents
  • two voltages
  • two or more similar electrical quantities
  • none of the above