QUIZ - 8



  1. The value of Xd″ for 2 pole Turbo alternator in the range of:
    • 0.07 to 0.12
      0.1 to 0.5
      1 to 5
      0.7 to 1.8


  2. The value of Xd″ for water wheel alternators in the range of:
    • 0.1 to 0.35
      1 to 3.5
      0.07 to 0.12
      0.7 to 1.2


  3. Which statement is correct just after fault:
    • Xd″= Xd′= Xd
      Xd″ < Xd′< Xd
      Xd″ >Xd′ >Xd
      None of these


  4. The reactances of a synchronous machine depend upon:
    • Applied Voltage
      Leakage flux
      Degree of saturation of magnetic core
      Power factor of supply current


  5. Line to line fault in a transmission line is a:
    • Symmetrical fault
      Unsymmetrical fault
      Somewhat symmetrical
      Somewhat unsymmetrical


  6. Selection of circuit breaker depends upon:
    • Current under normal operating condition
      (Current under normal condition) + (maximum current which flows momentarily)
      (Current under normal condition) + (maximum current which flows momentarily) +(interrupting current at given kV)
      None


  7. The short circuit current has:
    • Symmetrical component of current only
      D.C. off-set current only
      Both 1 and 2
      None of the above


  8. If θ ≈ 90 degree and α= 0, then maximum momentary current (imm) will be:
    • Half the maximum of symmetrical short circuit current
      Equal to the maximum of symmetrical short circuit current
      Four times to the maximum of symmetrical short circuit current
      Twice the maximum of symmetrical short circuit current


  9. The value of symmetrical short circuit current:
    • √2V/|Z|
      1/2(√2V/|Z|)
      1/4(√2V/|Z|)
      (1/√2)*(√2V/|Z|)

  10. The effective value of transient reactance when there is no damping current:
    • Xd′ = XL + Xa
      Xd′ = XL + Xf
      Xd′ = XL
      Xd′ = XL + (Xa || Xf)