Quiznetik
Switch Gear and Protection | Set 2
1. Oil switches are employed for
A. low currents circuits
B. low voltages circuits
C. high voltages and large currents circuits
D. all circuits
Correct : C. high voltages and large currents circuits
2. A switchgear is device used for
A. interrupting an electrical circuit
B. switching an electrical circuit 111.
C. switching and controlling an electrical circuit
D. switching, controlling and protecting the electrical circuit and equipment
Correct : D. switching, controlling and protecting the electrical circuit and equipment
3. The fuse wire, in D.C. circuits, is inserted in
A. negative circuit only
B. positive circuit only
C. both (a) and (b)
D. either (a) or (b)
Correct : C. both (a) and (b)
4. By which of the following methods major portion of the heat generated in a H.R.C. fuse is dissipated ?
A. Radiation
B. Convection
C. Conduction
D. All of the above
Correct : C. Conduction
5. A short-circuit is identified by
A. no current flow
B. heavy current flow
C. voltage drop
D. voltage rise
Correct : B. heavy current flow
6. The information to the circuit breaker under fault conditions is provided by
A. relay
B. rewirable fuse
C. H.R.C. only
D. all of the above
Correct : A. relay
7. To limit short-circuit current in a power system are used.
A. earth wires
B. isolators
C. H.R.C. fuses
D. reactors
Correct : D. reactors
8. A balanced 3-phase system consists of
A. zero sequence currents only
B. positive sequence currents only
C. negative and zero sequence currents
D. zero, negative and positive sequence currents
Correct : B. positive sequence currents only
9. In a single bus-bar system there will be complete shut down when
A. fault occurs on the bus itself
B. fault occurs on neutral line
C. two or more faults occur simultaneously
D. fault occurs with respect to earthing
Correct : A. fault occurs on the bus itself
10. Which device is used for protection of equipment from from damage caused by overload or short circuit?
A. CVT
B. Circuit Breaker
C. Current Transformer
D. Lighting Arrester
Correct : B. Circuit Breaker
11. Isolator in substation is open under ------------- condition?
A. No load
B. Short Circuit
C. Full Load
D. Any of the above
Correct : A. No load
12. Earthling switch is used for
A. measuring of safety voltage
B. protection of equipment from ground faults
C. discharging residual energies
D. all of the above
Correct : D. all of the above
13. If the time of operating of a relay for unity TMS is 10secs., the time of operation for 0.5 TMS will be
A. 20 secs.
B. 5 secs.
C. 10 secs.
D. None of the above
Correct : B. 5 secs.
14. A fault is more severe from the view point of RRRV if is a
A. Short line fault.
B. Medium length line fault.
C. Long line fault.
D. None of these.
Correct : A. Short line fault.
15. A reactance relay is
A. Voltage restrained directional relay.
B. Directional restrained over-current relay.
C. Voltage restrained over-current relay.
D. None of the above.
Correct : B. Directional restrained over-current relay.
16. For measuring positive, negative and zero sequence voltages in a system, the reference is taken as
A. Neutral of the system only.
B. Ground only.
C. For zero sequence neutral and for positive and negative the ground.
D. None of the above.
Correct : D. None of the above.
17. Positive, negative and zero sequence impedances of a solidly grounded system under steady state condition always follow the relations
A. Z4>Z2>Z0
B. Z2>Z4>Z0
C. Z0>Z4>Z2
D. None of the above
Correct : C. Z0>Z4>Z2
18. Phase comparators in case of static relays and electro-mechanical relays normally are
A. Sine and cosine comparators respectively
B. Cosine and sine comparators respectively.
C. Both are cosine comparators.
D. Both are sing comparators.
Correct : B. Cosine and sine comparators respectively.
19. For reducing tower footing resistance it is better to use
A. Chemical and ground rods only.
B. Chemical and counterpoise only.
C. Ground rod and counterpoise only.
D. Chemical, ground rods and counterpoise.
Correct : C. Ground rod and counterpoise only.
20. Rate of rise of restriking voltage depends
A. Type of circuit breaker.
B. Inductance of the system only.
C. Capacitance of the system only.
D. Inductance and capacitance of the system
Correct : D. Inductance and capacitance of the system
21. What is the purpose of back up protection?
A. To increase the speed
B. To increase the reach
C. To leave no blind spot
D. To guard against failure of primary
Correct : D. To guard against failure of primary
22. What is the actuating quantity for the relays?
A. Magnitude
B. Frequency
C. Phase angle
D. All of these
Correct : D. All of these
23. Protective relays can be designed to respond to
A. Light intensity, impedance
B. Temperature, resistance, reactance
C. Voltage and current
D. All of these
Correct : D. All of these
24. On what factor does the operating speed of the relay depend upon?
A. Rate of flux built up
B. Armature core air gap
C. spring tension
D. All of these
Correct : D. All of these
25. What does the third part consist of?
A. Primary winding of a current CT which is connected in series with the line to be protected.
B. Secondary of the CT and the operating coil.
C. Tripping circuit.
D. All of these.
Correct : C. Tripping circuit.
26. Which component ensures the safety of the line from damage?
A. Relay
B. Circuit breaker
C. Bus bar
D. Current tr
Correct : A. Relay
27. The tripping circuit is_
A. AC
B. DC
C. either AC or DC
D. None of these
Correct : C. either AC or DC
28. Plug setting of a electromagnetic relay can be altered by varying
A. Number of ampere turns
B. Air gap of magnetic path
C. Adjustable back stop
D. None of these
Correct : A. Number of ampere turns
29. the most efficient torque producing actuating structure for the induction type relays is
A. Shaded pole structure
B. Watt hour meter structure
C. Induction cup structure
D. Single induction loop structure
Correct : C. Induction cup structure
30. If the power factor is zero, the active recovery voltage will be
A. minimum
B. 0.5
C. 0.707
D. Maximum.
Correct : D. Maximum.
31. Which of the following is not a part of the circuit breaker?
A. Explosion pot
B. Fixed and moving contacts
C. Conservator
D. Operating mechanism.
Correct : C. Conservator
32. Which of the following circuit breaker will produce the least arc energy?
A. Minimum oil circuit breaker
B. Air blast circuit breaker
C. Plain oil circuit breaker
D. All will produce same energy.
Correct : B. Air blast circuit breaker
33. For a circuit breaker 'break time' is
A. Same as opening time
B. Opening time + arc duration
C. Opening time + arc duration + resistor current duration.
D. none
Correct : C. Opening time + arc duration + resistor current duration.
34. The breaking capacity of a circuit breaker in MVA (3 phase) is given by
A. Rated service voltage x rated symmetrical current
B. 1.1 x rated service voltage x rated symmetrical current
C. (2)1/2 x rated service voltage x rated symmetrical current
D. (3)1/2x rated service voltage x rated symmetrical current.
Correct : D. (3)1/2x rated service voltage x rated symmetrical current.
35. Which relay is used for feeders?
A. MHO relay
B. Translay relay
C. Merz price protection
D. Buchholz relay.
Correct : B. Translay relay
36. Which of the following relays is used on transformers?
A. Buchholz relay
B. MHO relay
C. Merz price relay
D. None of the above.
Correct : A. Buchholz relay
37. MHO relay is used for
A. Rectifiers
B. Circuit breakers
C. Transmission lines
D. Feeders.
Correct : C. Transmission lines
38. Merz-price protection is used on
A. Substations
B. Capacitor bank
C. Induction motor
D. Generators.
Correct : D. Generators.
39. The values of fault current depend on
A. Voltage at the faulty point
B. Total impedance up to the fault
C. Both (A) and (B) above
D. None of the above
Correct : C. Both (A) and (B) above
40. The advantage of neutral earthling is
A. Simplified design of earth fault protection
B. Over-voltages due to lightning can be discharged to the earth
C. Freedom from persistent arcing grounds
D. all of the above.
Correct : D. all of the above.
41. The over-voltage surges in power systems may be caused by
A. Lightning
B. Switching
C. Resonance
D. Any of the above.
Correct : D. Any of the above.
42. The protection against over-voltage due to lightening is provided by
A. Use of surge diverters
B. Low tower footing resistance
C. Use of overhead ground wires
D. Any of the above.
Correct : D. Any of the above.
43. Which of the following is a conducting medium for electric current ?
A. Low temperature gas
B. High temperature gas
C. Dissociated gas
D. Plasma.
Correct : D. Plasma.
44. In circuit-breakers the contact space is ionized by
A. Thermal ionization of gas
B. Thermal emission from surface of contacts
C. Field emission from the surface of contacts
D. Any of the above.
Correct : D. Any of the above.
45. Which of the following are air-break switching devices ?
A. Isolator
B. Limit switch
C. Earthling switch
D. All of the above.
Correct : D. All of the above.
46. Which of the following statement about SF6 gas is incorrect?
A. It is non-toxic gas
B. It is non-inflammable
C. It has density 5 times that of air at 200C
D. It has dark yellow color.
Correct : D. It has dark yellow color.
47. SF6 gas is transported in
A. Gas cylinders
B. Liquid form in cylinders
C. Solid form in boxes
D. Air cylinders.
Correct : B. Liquid form in cylinders
48. duringarc extinction SF6 gas
A. Decomposes into S and F ions
B. Decomposes into SF4and SF2
C. Gets oxidized
D. Reduces to SF3.
Correct : B. Decomposes into SF4and SF2
49. Dielectric strength of SF6 is
A. less than that of air at atmospheric pressure
B. less than that of oil used in OCB
C. more than that of oil used in OCB
D. More at lower pressure and low at higher pressures.
Correct : B. less than that of oil used in OCB
50. Which of the following is the demerit of SF6 circuit breakers?
A. Sealing problem of gas
B. In flux of moisture in the gas system is dangerous
C. Deterioration of quality of circuit breaker affects reliability of circuit breaker
D. All of the above.
Correct : D. All of the above.