Relays And System Protection

43 Questions | Total Attempts: 884

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Electrical Quizzes & Trivia

Questions and Answers
  • 1. 
    Which of the following relays operation is based on a direct proportion of the distance to the location of the fault
    • A. 

      Impedance relay

    • B. 

      Definite time relay

    • C. 

      Differential relay

  • 2. 
    What types of relay takes longer to detect a fault that is further away along the line?
    • A. 

      Impedance relay

    • B. 

      Differential relay

    • C. 

      Overcurrent relay

  • 3. 
    A type of relay in which the time of relaying varies directly as the distance of the fault from the station 
    • A. 

      Distance Relay

    • B. 

      Differential Relay

    • C. 

      Overcurrent

    • D. 

      Pilot

  • 4. 
    Which of the following types of relays are used to protect transformers and generators?
    • A. 

      Directional overcurrent Relays

    • B. 

      Differential Relay

    • C. 

      Thermal Relays

    • D. 

      Single Pole Relays

  • 5. 
    A type of relaying which is responsive to the direction of the flow of power and line impedance is normally designed as
    • A. 

      Distance relaying

    • B. 

      Pilot protection

    • C. 

      Power relaying

    • D. 

      Differential relaying/protection

  • 6. 
    Which drawing represents a Balanced Current Relay?
    • A. 
    • B. 
    • C. 
    • D. 
    • E. 
    • F. 
  • 7. 
    Which drawing represents a Under Current Relay?
    • A. 
    • B. 
    • C. 
    • D. 
    • E. 
    • F. 
  • 8. 
    Which drawing represents a Differential Relay?
    • A. 
    • B. 
    • C. 
    • D. 
    • E. 
    • F. 
  • 9. 
    Which drawing represents a Overcurrent (Non-Directional) Relay?
    • A. 
    • B. 
    • C. 
    • D. 
    • E. 
    • F. 
  • 10. 
    Which drawing represents a Pilot Wire  Relay?
    • A. 
    • B. 
    • C. 
    • D. 
    • E. 
    • F. 
  • 11. 
    The purpose of a differential relay on a transformer is to
    • A. 

      Protect against external faults

    • B. 

      Protect against internal faults

    • C. 

      Protect against overvoltage

    • D. 

      Protect against under current

  • 12. 
    Mho relay is normally used for the protection of: 
    • A. 

      Long transmission lines

    • B. 

      Medium length lines

    • C. 

      Short length lines

    • D. 

      No length criterion

  • 13. 
    Reactance relay is normally preferred for protection against:
    • A. 

      Earth faults only

    • B. 

      Phase Faults only

    • C. 

      3 phase to ground faults

    • D. 

      Single phase ground faults

  • 14. 
    This value is the determinant as to how long a short circuit will remain on a circuit, if uninterrupted by an overcurrent protective device.
    • A. 

      Time of fault

    • B. 

      At what point did the fault occur

    • C. 

      X/R

    • D. 

      Single or 3 phase

  • 15. 
    In the short circuit analysis, the rate of decay of fault current depends on:
    • A. 

      L/R ratio

    • B. 

      Single or 3 phase

    • C. 

      At what point did the fault occur

    • D. 

      Time of fault relative to the volatge

  • 16. 
    If the fault current is 2000 amps, the relay setting is 50% and the C.T. is 400/5, then the plug setting multiplier should be:
    • A. 

      25 amps

    • B. 

      15 amps

    • C. 

      50 amps

    • D. 

      None of the above

  • 17. 
    Magnitude of the short circuit depends least based on what?
    • A. 

      Circuit reactance

    • B. 

      Capacity of the generator

    • C. 

      Synchronous Reactance

    • D. 

      Circuit Resistor

  • 18. 
    What is not a possible zone of protection in a power system?
    • A. 

      Bus Bars

    • B. 

      Lines

    • C. 

      Capacitor or reactor banks

    • D. 

      Utilization equipment

    • E. 

      High pass filters

    • F. 

      Generators

    • G. 

      Transformers

  • 19. 
    How many protection zones are possible in a power system?
    • A. 

      7

    • B. 

      6

    • C. 

      5

    • D. 

      4

  • 20. 
    Which of the following is the most severe fault?
    • A. 

      Three phase fault

    • B. 

      Single line to ground

    • C. 

      Double line to ground fault

    • D. 

      Earth ground interrupt

  • 21. 
    What component is not normally used in the protection of a power system?
    • A. 

      Current Transformers (CTs)

    • B. 

      Variable Reactors

    • C. 

      Voltage Transformers (PTs)

    • D. 

      Coupling Capacitance Volatge Transformers (CCVTs)

  • 22. 
    The greatest effect of a fault on a system is on?
    • A. 

      Subtransient

    • B. 

      Steady State

    • C. 

      Transient

  • 23. 
    In adjacent overlapping zones in the DWP 500-kv systems, what component or device is normally overlapped?
    • A. 

      Relay

    • B. 

      Transformer

    • C. 

      Disconnect

    • D. 

      Circuit Breaker

  • 24. 
    The ratio of reset to pickup for an induction cup relay is approx:
    • A. 

      0.99

    • B. 

      1.01

    • C. 

      0.75

    • D. 

      None

  • 25. 
    If the time operation of a relay for unity TMS is 10 sec, what is the time of operation for 0.5 TMS:
    • A. 

      20

    • B. 

      5

    • C. 

      10

    • D. 

      None

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