1. What is a High Voltage Ground Condition
    6kv and above, indicated by the red area on GD meter
  2. Ungrounded phase to ground voltage
  3. BØ shows zero, AØ/CØ shows 4.8kv
    Conventional Ground
  4. AØ shows 1kv, BØ/CØ shows 4kv
    Partial AØ Ground - AØ conductor is connected to Ground through some impedance
  5. True/False

    I High Voltage Ground may have more than one phase at 6kv or above
  6. With a High Voltage Ground, the grounded phase or phases cannot always be determined by                        .
  7. BØ phase GD reads zero, AØ and CØ GD reads 2.77kv
    Blown BØ GD fuse
  8. True/False

    If the GDs on all three phases read zero, than the fuses on all three phases are blown
    False - could also be a High Voltage Ground or Unusually High voltage Ground and needs to be investigated
  9. True/False

    In Package Style Stations, Reset the ground alarm at the banks when the GD meters read normal to clear old alarms
  10. In Package Style Stations, the                  is blocked on all units with grounded circuits
    automatic transfer switch (ATS)
  11. In Package Style Stations, what prevents the feeder circuit breakers (CB) from reclosing
    Blocking the ATS
  12. In Package Style Stations, the auto reclosers (AR) are blocked on all units with                      , if available
    grounded circuits
  13. True/False

    In Package Style Stations, the bank load ratio controllers (LRC) are blocked on neutral on both banks in the position (one bank is the grounded bank, and one bank is ungrounded)
  14. Paralleling banks during a ground condition will sometimes change conventional grounds into             or              grounds
    high voltage, unusually hazardous high voltage
  15. True/False

    During a Conventional Ground Search in a Non-Package Station, Auto Reclosers (AR) are to be blocked on all feeder circuits
  16. During a Conventional Ground in a Non-Package Station, test only those circuits being supplied from the affected              
    for grounds
    4.8-kV bus
  17. What equipment cannot be tested in a 4.8kv ground search
    4.8kv Ground Detectors, 4.8kv cables, Banks
  18. What do you do is the Bank is suspected of being grounded
    • Notify the LD and obtain a Work Authority for testing and analysis of equipment.
    • Contact the ACO so the ESM may be advised of the suspected grounded equipment.
  19. What do you do if Station Service is grounded
    • Contact the LD
    • Contact the ACO to have ESM begin repairs and/or supply a portable generator so critical Station service load may be supplied
  20. True/False

    An intermittent conventional ground is not searched
  21. True/False

    Intermittent and High Voltage and Unusually High Voltage  grounds are searched as though they are not intermittent if the ground indications are stable enough to draw conclusion from switching
  22. True/False

    A multiple ground condition may be indicated when, after a circuit is dropped, a ground is still indicated, but with different voltage reads
  23. What do you do if multiple grounds exist
    Stop the ground search and notify the Load Dispatcher and Electric Trouble Dispatcher (ETD).
  24. True/False

    Do not parallel banks if multiple grounds exist, whether on the same phase or not. If the grounds are on different phases, paralleling the banks will usually cause a short circuit
  25. What is the basic insulation level (BIL) for 4.8-kV equipment
    7.2-kV for older equipment, or 15-kV for newer equipment
  26. What is the biggest safety risk regarding High Voltages grounds
    • Phase-to-ground voltages may exceed the voltage rating of insulators and bushings, which presents an extreme safety risk
    • because a flashover may occur at the weakest point of insulation
  27. What should you do upon identifying a High Voltage Ground
    Notify the Electric Trouble Dispatcher (ETD) as soon as possible, in order to alert the field crews about the hazardous condition
  28. True/Fasle

    During a high voltage ground search, leave de-energized any feeder that reduces or eliminates the ground condition. These feeders are tested only on the orders of the LD
  29. If upon de-energizing a feeder, the high voltage ground
    becomes a                  , the high voltage ground
    search is continued until all grounds have cleared
    conventional ground
  30. What should be reported and to whom during a High Voltage Ground Search
    • ETD and the LD 
    • Report which feeders cleared or reduced the high voltage
    • ground indication
    • Report the results of the testing of feeder positions
  31. True/False

    In an Usually High Voltage Ground situation, if there are more feeders that caused a conventional ground than there are separate, ungrounded sources, contact the LD for restoration instructions
  32. During a conventional ground search, why must the time in which the Banks are in // be minimized as much as possible
    • Because of increased fault capacity
    • The ground condition may be worsened by paralleling banks
  33. True/False

    The Load Dispatcher (LO), ETD and the Operator must agree prior to performing any bank switching during ground searches
  34. True/False

    Overloads are permissible while performing a ground search using the Transfer method, but should be minimized as much as possible
  35. If there was a ground on a GD or                    the fuse may have blown
    potential transformer
  36. A bank showing a ground on its GD meters, but the transformer itself is not grounded
    Grounded Bank
  37. A bank showing normal GD reads
    Ungrounded Bank
  38. During a conventional Ground search, If all load is transferred off the 4.8-kV bus, and the location of the ground has not been determined, what steps are necessary to determine the location of the ground
    • Verify that any 4.8-kV bus connected capacitors are off.
    • Supply the bus or bus section with the load transferred off from an ungrounded source.
    • If the previously ungrounded bank becomes grounded, then the ground is on the 4.8-kV bus or bus section
  39. What is one of the issues with an ungrounded system
    A high-voltage condition. This can be caused by the traditional theory on ferroresonance, or by a DC offset transient overvoltage due to re-striking (arcing grounds) or intermittent ground faults
  40. When the inductive impedance (such as in the Distribution Bank) equals the capacitive impedance of the system (feeders).
  41. An arcing ground on the system.
    DC offset high voltage condition
  42. The persistence of the arc due to the flow of capacitive current causes a condition known as "                " in which cyclic charging and discharging of the system capacitance though
    the fault results in high frequency oscillations being superimposed on the whole system and a buildup of very
    high voltages can occur.
    arcing ground
  43.            voltages are practically unchanged whereas           are dramatically affected due to shifting of the ungrounded neutral with respect to ground
    Phase-to-phase, phase-to-ground voltages
  44. One phase connected to ground does not cause the circuit to relay because of the Department's closed delta                system
  45. A ground where the meter for the grounded phase
    reads zero or close to zero, and the meters for the other two phases read between 4.8-kV and 6.0-kV, usually close to 4.8-kV
    conventional ground
  46. SAS
    Substation Automation System (SAS).
  47. What are causes a false ground alarm
    • Blown Fuses
    • Bank carrying little to no load
    • Nature of Field Load (stations with ungrounded feeders
  48. What may be the cause of a Partial Grd
    A partial ground may be caused by the grounded phase having a high resistance to ground

    A partial ground may be caused by more than one ground on the same phase, one of which is a partial ground
  49. A ground that moves from one phase to another phase.
    Intermittent grounds
  50. True/False

    Any ground condition can appear as an intermittent ground
  51. What can casue conventional grounds to turn into high voltage grounds
    • Ferroresonance or DC transient overvoltage conditions.
    • Trouble in the station and/or field.
    • Station and or field switching
  52. Unusual station conditions that identify an unusually hazardous high voltage ground are indicated by one or more GD meters reading over 6-kV and one or more of the following conditions
    • Ferroresonance or DC transient overvoltage conditions (arcing grounds).
    • Trouble in the station and/or field.
    • Station and or field switching
  53. True/False

    The Operator may isolate the failed equipment before notifying
    the LD and requesting a Work Authority
  54. True/False

    Any Power System employee can declare an emergency and
    request a feeder to be de-energized immediately
  55. Why are capacitors taken off during a 5kv ground search
    The capacitors are taken off to reduce ferroresonance and high voltage conditions
  56. True/False

    Separate banks that are in parallel, such as in Gas Co. style stations, or stations where two banks normally supply one 4.8-kV bus
Card Set
Handling 4.8kv Grds