Switch Gear and Protection Mid - II, November - 2014

1.Which of the following grounding methods is used to reduce the tower footing resistance where an earth resistance is low?
  • single driven rod
  • multiple rods
  • counter poises
  • plates
Answer: A
2.Impulse ratios of insulators and lightning arresters should be
  • both low
  • high and low
  • low and high
  • both high
Answer: B
3.To protect the power transformer (Y-Y with neutral grounded) against fault what type of connection do the CTS have?
  • delta – star
  • delta-delta
  • star – star
  • star-delta
Answer: B
4.Which is the main relay for protecting up to 90% of the transmission line length in the forward direction?
  • directional over current relay
  • mho relay
  • carrier current relay
  • impedance relay
Answer: B
5.The rating of lightning arrester used for 220KV, 3 phase system is
  • 220KV,10KA
  • 220KV,5KA
  • 198KV,10KA
  • 198KV,2KA
Answer: C
6.Severe over voltages are produced during arcing faults in a power system with the neutral
  • isolated
  • solidly earthed
  • earthed through a low resistance
  • earthed through an inductive coil
Answer: A
7.In the protection of transformers, harmonic restraint is used to guard against
  • magnetizing inrush current
  • unbalanced operation
  • lightning
  • switch over voltages
Answer: A
8.The various protection schemes as applied to feeder protection
  • time graded protection
  • distance protection
  • carrier current protection
  • All the above
Answer: D
9.Which of the following is true with respect to valve type lightning arrester?
  • also known as non linear arresters
  • consist of a stack of spark gaps and resistor discs
  • ohmic value decreases as current increases
  • All the above
Answer: D
10.The common transformer faults are
  • open circuits
  • over heating
  • winding short circuits
  • All the above
Answer: D
11.The method of grounding by insertion of a reactance is called as __________ grounding.
Answer: Reactance
12.In resonant grounding, the function of the ______________ coil is to make arcing earth faults self extinguishing.
Answer: Arc suppression
13.The valve type arresters can be classified as ___________ and __________types.
Answer: Station and line
14.In a transformer ____________ relays protect against phase to phase faults and overloading.
Answer: Over current
15.The ideal scheme of protection for lines is ________________.
Answer: Differential
16.The two most commonly used schemes for bus bar protection are ______________ and ________________.
Answer: Differential and fault bus protection
17.A _________________ connected to the line and earth in power system protects the terminal equipment against travelling surges.
Answer: Lightning arrester
18.A ________________ relay is used for protection of a transformer against all internal faults.
Answer: Buchholz
19._______________ grounding is normally employed on systems operating at voltages between 2KV and 33KV.
Answer: Resistance
20.Bus bar zone, for the protection includes _____________________________.
Answer: Isolating switches and circuit breakers