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)