Circuit Breakers Part 3
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Attempt Free Circuit Breakers Part 3 Here. Read The Important Electrical MCQ From Below.
Instructions: Click the answer button to see the correct answer.
Ques. Which of the following is a conducting medium for electric current ?
- Dissociated gas
- Low temperature gas
- High temperature gas
- Plasma.
Answer: d
Ques. In circuit-breakers the contact space is ionized by
- thermal emission from surface of contacts
- any of these
- thermal ionization of gas
- field emission from the surface of contacts
Answer: b
Circuit Breakers Part 3
Ques. Which of the following are air-break switching devices ?
- Earthing switch
- Isolator
- All of these
- Limit switch
Answer: c
Ques. Which of the following statement about SF6 gas is incorrect ?
- It has density 5 times that of air at 20 C
- It is non-inflammable
- It has dark yellow color.
- It is non-toxic gas
Answer: c
Circuit Breakers Part 3
Ques. SF6 gas is transported in
- liquid form in cylinders
- gas cylinders
- solid form in boxes
- air cylinders.
Answer: a
Ques. During arc extinction SF6 gas
- decomposes into SF4 and SF2
- decomposes into S and F ions
- gets oxidized
- reduces to SF3.
Answer: a
Ques. Dielectric strength of SF6 is
- less than that of air at atmospheric pressure
- less than that of oil used in OCB
- more than that of oil used in OCB
- more at lower pressure and low at higher pressures.
Answer: b
Ques. Which of the following is the demerit of SF6 circuit breakers ?
- All of these
- Deterioration of quality of circuit breaker affects reliability of circuit breaker
- In flux of moisture in the gas system is dangerous
- sealing problem of gas
Answer: a
Circuit Breakers Part 3
Ques. Sphere gaps are used for
- all of these
- measurement of impulse voltages
- measurement of high dc voltages
- measurement of high ac voltages
Answer: a
Ques. Flash point of dielectric is usually above
- 240°C.
- 100°C
- 80°C
- 140°C
Answer: d
Ques. A fuse is normally a
- power factor correcting device.
- power limiting device
- current limiting device
- voltage limiting device
Answer: c
Circuit Breakers Part 3
Ques. Most of the fuses operate due to
- magnetic effect of current
- electrostatic effect of current
- none of these
- heating effect of current
Answer: d
Ques. Normally the fuse elements are in parts which are connected in the middle by ten bridge. The melting point of tin bridge is
- 88°C
- 230°C
- 35°C
- 540°C.
Answer: b
Ques. The voltage across the circuit breaker pole after final current zero is recovery voltage.
- false
- true
Answer: b
Ques. Air circuit breakers are used for voltages above 12 kV.
- false
- true
Answer: a
Circuit Breakers Part 3
Ques. Double pressure type SF6 circuit breaker is also known as Puffer type.
- true
- false
Answer: b
Ques. Air blast circuit breakers and SF6 circuit breakers are preferred for EHV applications.
- true
- false
Answer: a
Ques. Arcing contacts of circuit-breakers are generally made of copper tungsten alloy.
- true
- false
Answer: a
Ques. The arc plays important role in the behavior of circuit breaker.
- true
- false
Answer: a
Ques. The arc has a brightly burning core of high temperature ranging from 6000 K to 25000 K.
- false
- true
Answer: b
Circuit Breakers Part 3
Ques. SF6 is a heavy, colorless and chemically inert gas.
- false
- true
Answer: b
Ques. SF6 gas is electro-positive.
- false
- true
Answer: a
Ques. In oil circuit breakers transformer oil is used.
- true
- false
Answer: a
Ques. An isolator does not have any current making or current breaking capacity.
- true
- false
Answer: a
Ques. SF6 circuit breaker takes minimum time for installation.
- true
- false
Answer: a
Circuit Breakers Part 3
Ques. A triple pole isolator has three identical poles, with operate simultaneously.
- false
- true
Answer: b
Ques. Isolators operate under no current conditions.
- false
- true
Answer: b
Ques. Non-linear resistors are used in lightning arresters.
- false
- true
Answer: b
Circuit Breakers Part 3
Ques. Switching over-voltages are proportional to system voltages.
- true
- false
Answer: a
Ques. Switching over-voltages arise from energizing of uncharged line can be reduced by the use of high voltage shunt reactors.
- false
- true
Answer: b
Ques. The damage caused by surge depends on steepness of the wave-front.
- false
- true
Answer: b
Ques. Bulk oil circuit breaker is used for outdoor UHV application.
- true
- false
Answer: b
Ques. In electro-magnetic relays the restraining torque is given by springs.
- false
- true
Answer: b
Circuit Breakers Part 3
Ques. For remote operation circuit-must breaker be equipped with shunt trip.
- false
- true
Answer: b
Ques. A protective system which responds to vector difference between two electrical quantities is known as differential protection.
- true
- false
Answer: a
Ques. Protective systems prevent faults by disconnecting an equipment in the event of abnormal condition.
- false
- true
Answer: b
Ques. Selectivity is the property by virtue of which the protective relaying system distinguishes between normal condition and abnormal condition.
- true
- false
Answer: a
Circuit Breakers Part 3
Ques. Frequency relays are used in generator protection.
- false
- true
Answer: b
Ques. SF6 circuit breaker has high reliability and negligible maintenance.
- false
- true
Answer: b
Ques. Tripping relays are slow and generally attracting armature type.
- false
- true
Answer: a
Ques. The over-current relays are connected to the system normally by means of CT’s.
- true
- false
Answer: a
Circuit Breakers Part 3
Ques. Core balance CT’s are used for earth-fault protection.
- false
- true
Answer: b
Ques. Short circuit tests are conducted on circuit breakers to prove the ratings of the circuit-breakers.
- true
- false
Answer: a
Ques. Fusing factor is the ratio of minimum fusing current to the current rating.
- true
- false
Answer: a
Ques. The distance protection responds to the ratio V/I.
- true
- false
Answer: a
Ques. Graded time lag and grade current over-current protection is used for single radial feeder where time lag can be permitted.
- true
- false
Answer: a
Circuit Breakers Part 3
Ques. Distance relaying is based on measurement of impedance between relay location and fault point.
- false
- true
Answer: b
Ques. Distance relay is used where time lag can be permitted.
- false
- true
Answer: a
Ques. Pilot wire differential relaying is used for lines up to 40 km of length.
- false
- true
Answer: b
Ques. In motor starter, thermal relay provides overload protection as well as single phasing protection.
- false
- true
Answer: b
Circuit Breakers Part 3
