### Testing And Commissioning Of Electrical Equipment’S Set 8

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 8

Q1 | The heat produced at the contact point owing to flow of electric current is leastaffected by_____________________.
• Temperature of the surrounding medium.
• Contact resistance.
• Magnitude of electric current flowing.
• Duration of flow of current.
Q2 | The resistance of an electric arc can be increased by
• Increasing the concentration of ionised particles.
• Reducing the arc length.
• Splitting the ar(C)
• Increasing the arc cross section.
Q3 | By using low resistance method for arc extension what is the value of arcresistance?
• Arc resistance is zero.
• Arc resistance is high
• Arc resistance is low
• Arc resistance is very high
Q4 | What happens in the arc extinction using high resistance method?
• Arc resistance is decreased with time.
• Arc resistance is increased with time.
• No change it remains same.
• Arc resistance is kept zero.
Q5 | What is the arc voltage in a circuit breaker?
• In phase with the arc current.
• Lagging the arc current by 90°
• Leading the arc current by 90°
• Lagging the arcing current by 180°
Q6 | Arcing voltage will be the least in case of
• Carbon
• Copper
• Silver
• Tungsten
Q7 | How is the initiation of electric arc at the instant of contact separation caused?
• Thermionic emission of electrons.
• Field emission of electrons.
• Both (a) and (b)
• None of these.
Q8 | The arc resistance depends on which among the following factors?
• Cross section of the ar(C)
• Length of the ar(C)
• Degree of ionization
• All of the above.
Q9 | Which type of tripping is generally preferred for the circuit breaker?
• Manual
• Automatically
• Depending on the voltage level
• None of the above
Q10 | Which part of the circuit breaker is helpful in breaking the current?
• Trip coil.
• Contacts.
• Medium
• Handle.
Q11 | When a fault occurs in a high voltage transmission line, what happens first?
• Circuit breaker operates then the relay.
• Relay operates and then the circuit breaker.
• Relay operates, then successively the isolator and the circuit breaker.
• Isolator operates, then successively the relay and the circuit breaker.
Q12 | Upto what voltage can the liquid type HRC fuses be used?
• 33 kV
• 132 kV
• 66 kV
• 220 kV
Q13 | What is the main advantage of using a fuse?
• Cheapest type of protection.
• Inverse time current characteristics.
• Current limiting effect under short circuit conditions.
• All of above.
Q14 | On what basis is the selection of fuse done?
• Fluctuating loa(D)
• Both (a) and (b)
• None of these.
Q15 | Upto what voltage a cartridge type of fuse can be used?
• 400 V
• 11 kV
• 20 kV
• 33 kV
Q16 | In a HRC fuse what is the time between the cut off and the final current zerocalled?
• Pre - arcing time.
• Arcing time.
• Total operating time.
• None of these.
Q17 | Which material is used in the liquid type of fuse?
• SF6
• Distilled water
• Carbon tetra chloride.
• Mineral oil / transformer oil
Q18 | What is the advantage of HRC fuses over Rewirable fuses?
• High speed operation
• High rupturing capacity
• No ageing effect.
• All of the above.
Q19 | If the strands of the fusing wire are twisted, what happens to the fusing current?
• Increases
• Reduces.
• No change/ remains same
• Depends on the value of current, increases or decreases.
Q20 | What is the typical value of the pre arcing time?
• 0.1
• 0.01
• 0.001
• 0.0001
Q21 | Outdoor switchgear is generally used for voltage beyond
• 11 KV
• 33 KV
• 66 KV
• 132 KV
Q22 | The least expensive protection for over current in low-voltage system is
• Rewirable fuse
• Isolator
• Circuit breaker
• Air-break switch
Q23 | Purpose of backup protection is
• To increase the speed
• To increase a reach
• To leave no blind spot
• To guard against failure of primary
Q24 | We do not require any protection against prime mover failure in case of
• Turbo generator sets
• Hydro generator sets
• Diesel engine driven alternators
• Back pressure turbo generators
Q25 | For the protection of stator winding of an alternate against internal fault involvingground the relay used is a
• Biased differential relay
• Directional over-current relay
• Plain impedance relay
• Buchholz relay