Testing And Commissioning Of Electrical Equipment’S Set 6

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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 6

Q1 | On what factor does the operating speed of the relay depend?
  • Rate of flux built up
  • Armature core air gap
  • Spring tension
  • All of these
Q2 | Protective relays can be designed to respond to ___________.
  • Light intensity, impedance
  • Temperature, resistance, reactance
  • Voltage and current
  • All of these
Q3 | What is the purpose of back up protection?
  • To increase the speed
  • To increase the reach
  • To leave no blind spot
  • To guard against failure of primary
Q4 | What is the major cause of the failure of the circuit breaker?
  • Trip circuit open
  • Trip latch defective
  • Spring defective
  • All of these
Q5 | Why are the isolators used?
  • Break abnormal current
  • Making under fault conditions
  • Breaking the circuit under no load condition
  • None of the above
Q6 | The isolators used in the transmission lines are capable of breaking
  • Fault current
  • No current
  • Charging current
  • Load current
Q7 | For which among the following the current ratings are not required?
  • Circuit breakers
  • Relays
  • Isolators
  • Load break switch
Q8 | What is the making to breaking current ratio for an extra high voltage circuit breaker?
  • More than 1
  • Equal to 1
  • Less than 1
  • A negative value
Q9 | The breaking capacity of a three phase circuit breaker is given by
  • Service line voltage * rated symmetrical current in amperes * 10-6 MVA
  • ?3 * Service line voltage * rated symmetrical current in amperes * 10-6 MVA
  • 1.1* Service line voltage * rated symmetrical current in amperes * 10-6 MVA
  • ?2 * Service line voltage * rated symmetrical current in amperes * 10-6 MVA
Q10 | Which of the following circuit breaker is highly reliable and has a least maintenance?
  • Oil circuit breakers
  • Air blast
  • Vacuum circuit breakers
  • SF6 circuit breakers
Q11 | The rating of the circuit breaker is usually determined on the basis of ____________ fault.
  • Symmetrical
  • Line to line
  • Single line to ground
  • Double line to ground
Q12 | Which among these circuit breakers produce the least arc energy?
  • Plain oil
  • Minimum oil
  • Air blast
  • Air break
Q13 | A thermal protection switch provides protection against what?
  • Overload
  • Temperature
  • Short circuit
  • Over voltage
Q14 | What does protective relay provide?
  • Provide additional safety to the circuit breaker in its operation.
  • Close the contacts when the actuating quantity attains a certain predetermined value.
  • Limit the arcing current during the circuit breaker operation.
  • Earth or ground any stray voltage.
Q15 | What is the main purpose of oil in oil circuit breakers?
  • Provide insulation
  • Quenching ar(C)
  • Provide cooling of contacts.
  • None of the above
Q16 | What is the advantage of using oil as the arc quenching medium?
  • Good cooling properties.
  • High dielectric strength.
  • Acts as an insulator.
  • All of these.
Q17 | When does the arc interruption in oil circuit breaker take place?
  • Contacts apart.
  • Voltages becomes zero
  • Current goes through zero
  • All of the above
Q18 | For rural electrification in India, which circuit breaker is generally used?
  • Oil
  • SF6
  • Vacuum
  • Air blast
Q19 | Keeping in view the cost and the overall effectiveness, which of the following circuit breaker is best suited for capacitor bank switching?
  • Vacuum circuit breaker
  • Air blast CB
  • SF6
  • Oil CB
Q20 | To limit current chopping in vacuum circuit breakers, the contact material employed should have the properties of
  • Low conductivity and high vapour pressure.
  • Low conductivity and low vapour pressure.
  • High conductivity and high vapour pressure.
  • High conductivity and low vapour pressure.
Q21 | SF6 gas is imported in _____________.
  • Air cylinders
  • Gas cylinders
  • Liquid form in cylinders
  • Solid form.
Q22 | During arc extinction SF6 gas gets converted to which among these?
  • Gets decomposed to SF4 and SF2
  • Gets decomposed to S and F
  • Gets reduced to SF6
  • Gets oxidized
Q23 | What is the most important property which makes the SF6 very efficient medium for circuit breaking?
  • Is non toxic and non inflammable.
  • Has a high dielectric constant.
  • Has a high breakdown strength
  • Is highly electronegative gas
Q24 | What is the normal pressure at which the SF6 gas is maintained in the closed position of the breaker?
  • 2 kg / cm2
  • 2.5 kg /cm2
  • 2.8 kg / cm2
  • 3 kg / cm2
Q25 | What is the major drawback of using SF6 circuit breakers?
  • Sealing problems of the gas.
  • Ingress of moisture in the gas system – dangerous.
  • Deterioration of SF6 gas with time.
  • Both (a) and (b)