High Voltage Engineering Mid - I, September - 2014

1.An experimental method for computing the field distribution is
  • Solution of Laplace equation
  • Electrolytic tank method
  • Digital simulation
  • Field intensity method
Answer: B
2.Most suitable numerical method to solve electrostatic field problems is
  • Laplace equation method
  • Charge simulation method
  • Finite difference method
  • Resistance analog method
Answer: B
3.The most commonly used liquid for transformer insulation is
  • Mineral oil
  • Askerals
  • Silicone oil
  • Polyester oils
Answer: A
4.The insulation used in high voltage circuit breakers of large power rating is
  • Air
  • Vacuum
  • SF6
  • Mineral oil
Answer: C
5.Ionization coefficients α, γ are functions of
  • Applied voltage
  • Pressure and temperature
  • Electric field
  • Ratio of electric field to pressure
Answer: D
6.Which of the following gas is a electronegative gas?
  • Air
  • O2
  • SF6
  • Both O2 and SF6
Answer: D
7.The intrinsic breakdown strength of solid dielectrics is about
  • 50 to 100 kV/mm
  • 500 to 1000 kV/mm
  • 5 to 10 kV/mm
  • 1 to 5 kV/mm
Answer: B
8.Paper insulation is mainly used in
  • Cables and capacitors
  • Transformers
  • Rotating machines
  • Circuit breakers
Answer: A
9.In testing with a resonant transformer, the output voltage is
  • Rectangular wave
  • Triangular wave
  • Trapezoidal wave
  • Pure sine wave
Answer: D
10.Peak to peak ripple is defined as
  • The difference between average dc voltage and peak value
  • The difference between maximum and minimum dc voltage
  • The difference between maximum ac and average dc voltages
  • The difference between ac (rms) and average dc voltages
Answer: B
11.The best insulation among all insulating materials available is _______________.
Answer: Vacuum
12.The most commonly used liquid as insulating medium is ______________.
Answer: Mineral oil
13.Impurities in insulating materials reduce _____________.
Answer: Breakdown strength
14.The parameters that affect the breakdown strength of liquids are ______________.
Answer: Pressure, temperature, dissolved impurities and suspended particles
15.The operating temperature of polyethylene insulation is ___________________.
Answer: -50°C to 80°C
16.Electromechanical breakdown occurs when the thickness due to electrical stress is compressed or reduced to about _______________.
Answer: 0.6 mm
17.Time to front of a impulse voltage waveform is defined as ______________.
Answer: 1.2 times the interval between 0.1 to 0.9 of peak value
18.The voltage efficiency of a normal impulse generator for generation of switching impulses is ___________________.
Answer: 40 to 60 %
19.In an impulse current generator the capacitors are connected in _________________.
Answer: Parallel
20.The energy rating of different resistor in impulse generators of medium and large size is ______________.
Answer: 2 to 5 KJ