Mine Electrical Engineering Mid - I, September - 2014

1.In solidly earth neutral system the fault current could be very high there for several hundred amps up to
  • 1 to 635 amps
  • 635 to 2000 amps
  • 627 to 827 amps
  • 635 to 735amps
Answer: B
2.A current limiting impedance is inserted between the star point and earth of such value as to limit the earth fault current to a maximum of
  • 650mA
  • 750mA
  • 700m
  • 625mA
Answer: A
3.He sensitivity of multipoint earth leakage detection circuits is standardized at a minimum of
  • 50 kilo ohm
  • 60kilo ohm
  • 70kilo ohm
  • 40kilo ohm
Answer: B
4.In ear thing side of a square pit can be obtained when x =
Answer: A
5.Arc control is an important factor in the design of a
  • Isolator
  • circuit breaker
  • oil circuit breaker
  • switch gear
Answer: D
6.SF6D type mining switch gear can be used on systems up to _________ in mines
  • 2.6kv
  • 3.6k
  • 5.6
  • 6.6kv
Answer: D
7.In mining _________ causes of short circuit is due to external causes
  • 40%
  • 50%
  • 90%
  • 70%
Answer: C
8.If the cross section is doubled the current will increase only ____ where are the cable weight increases approximately linearly with the cross section
  • 10%
  • 20%
  • 50%
  • 100%
Answer: C
9.A cable should not normally be regarded as satisfactory unless all insulation resistance is
  • 1 me ohm
  • 2 me ohm
  • 3 me ohm
  • 4 me ohm
Answer: A
10.The values are for one power conductor and are expressed in milli ohm per
  • 100m
  • 250m
  • 500m
  • 1000m
Answer: C
11.In earthing resistivity of coke breeze is _________
Answer: 40OHM-CM
12.Circuit breakers are designed as __________
Answer: DISTRIBUTION SWITCHES
13.Isolators in a circuit breaker are used to disconnect a circuit from __________ when work has to be carried out on the circuit.
Answer: LIVE BUS BAR
14.__________ & __________ are now used in underground mines and gradually replace the OCBs
Answer: sf6 & vacuum contactors
15.Gate end box is a ______________ enclosure.
Answer: flame proof
16.All mine cables are used in mines are manufactured according to ____________
Answer: IS(international standards)\
17.Trailing cables are used for ___________________
Answer: Supplying portable equipment
18.When laying cable the radius should be _____________ as possible.
Answer: Large
19.Mining cable needs _____________ to ensure safety.
Answer: Constant maintenance
20.The tests and inspections regarding ___________ & _____________ need to be made regularly in the routine maintenance of cables.
Answer: INSULATION CONDUCTIVITY