DS Buses

  1. There are three major
    components to a tap changer. These are:
    • • Motor Drive Mechanism
    • • Tap Changer Assembly
    • • Tap Connections to the Bank Winding
  2. The Energy Control Center is specifically responsible for coordinating
    voltage control throughout the DWP Power System
  3. If the output voltage is too low, the generator may
    • fall out of synchronism
    • with the Power System.
  4. The two major types of banks used for voltage control at receiving
    stations are:
    • • Main power banks
    • • Line banks
  5. Unlike synchronous condensers, static capacitors provide a
    • a fixed VAR
    • loading.
  6. Synchronous condensers can either supply or consume VAR
    • VAR closer to
    • the load than the generators. This relieves generators of VAR and
    • reduces line losses.
  7. Synchronous condensers make variable adjustments for
    • smooth
    • voltage control
  8. Synchronous condensers are normally connected to
    13.8kV tertiary winding of main power banks.
  9. Main power banks at receiving stations reduce voltage to the
    subtransmission voltage level.
  10. tertiary winding on a bank connects
    the condenser to the bank
  11. Some line banks have LTCs that can affect
    the transmission voltage
  12. Distributing
    station banks with either LTCs or LRCs can directly and automatically
    adjust the distribution voltage
  13. Most step regulators have a neutral plus
    • 16 5/8% steps up and 16 5/8%
    • steps down. This provides a total of 33 different settings.
  14. Pole-top static capacitors provide
    VAR close to the load for the greatest efficiency
  15. Any malfunction in voltage control equipment that prevents the
    equipment from maintaining voltage schedules is
    Class A trouble
  16. + VARs vs - VARS
    • +VARS going down stream to: going out
    • -VARS go up steam :coming in
  17. Putting more bank
    capacity on
    on raises voltage off lowers voltage
  18. Increasing the field voltage raises voltage and increases
  19. Decreasing the field voltage lowers voltage and
    decreases VAR
  20. While 34.5kV capacitors are usually
    bus connected, 4.8kV capacitors may be connected
    • to either a bus or a
    • bank.
  21. Increasing Voltage increases
  22. You should check voltage regulators for automatic operation. Do this
    • • Taking the regulator on manual   control
    • • Run three (3) steps in either       direction
    • • Check that the regulator returns to   approximately the same step
    •  automatically
  23. If you are unable to repair the regulator, block it on
    • a compatible step
    • and report
  24. Law of Electrical Charges is a
    fundamental law of electricity. It states, in part,
    , that unlike-charges attract and like-charges repel.
  25. The pressure or force that causes free electrons to move in a conductor
    is referred to as either
    • • Electromotive Force
    • • Difference in Potential
    • • Voltage
  26. The speed of current is
    constant 186000 mph
  27. One ohm is defined as
    • as the resistance of a circuit that permits a steady current of
    • one ampere to flow when one volt is applied to a circuit
  28. The lower case letter m stands for milli or the fraction
    one thousandth.
  29. Ohm's law can be expressed in the equation
    E = I × R
  30. P= I*E
  31. Calculating resistance in series
    add them together
  32. Calculating resistance in paralell
    1/Rt = 1/R1+ 1/R2 + 1/R3 ect.
  33. R.eq formula
    • Req = R1*R2
    •           _______
    •           R1 + R2
  34. Resistance   AC
    The opposition to current flow that is produced merely by aconductor's inability to perfectly conduct current is resistance.
  35. Capacitive Reactance
    • Electrostatic fields surround all conductors that are energized.
    • The transfer of energy through this  electrostatic field is known as CAPACITANCE. Capacitance reacts to changes in the circuit voltage.

    • The greater the "rate of change" in voltage, the greater the capacitance
    • on the circuit
  36. Inductive vs Capacitive
    • ELI 
    • Volt leads current

    • ICE
    • Current leads Voltage
  37. The formula for power factor in an AC circuit is:
    pf= R ÷ Z
  38. Power factor formula
    Pf= TP / AP
  39. True power is
  40. Apparent power is
    VARs  ie. VA
  41. If you know the value of the LINE amps, you can find the value of the
    phase amps by the following formula
    Aφ = AL/1.73
  42. how to calculate the amperage of a WYE line
    The phase equals the line
  43. how to calculate the voltage of a line from the phase

    WYE System
    V of phase = VLine / 1.73
  44. how to find voltage of a line in a DELTA system
    Vphase = Vline
  45. Diff between formula for WYE and DELTA
    • DELTA : voltage the same line
    •             Amp =  amps / 1.73

    WYE : amps the same as line
  46. A transformer is basically two sets of coils on a magnetic core of some
    kind. It has no moving parts and works on the principle of
    • mutual
    • induction.
  47. When a load is applied to the secondary windings, load current will
    appear in both windings. These currents are
    inversely related to the turns-ratio of the windings.
  48. The flow of current in the primary circuit is governed by three factors:
    • • Characteristics of the source, voltage and frequency
    • • Impedance of the winding
    • • Strength and direction of the magnetic field in the iron core.
  49. The voltage induced in the secondary coil is also governed by three
    • Strength and direction of the         magnetic field in the iron core.

    • • Rate of change in the magnetic field
    • • Number of turns in the coil.
  50. Eddy currents are circulating currents that are
    induced in the core of a transformer. They are the result of the alternating magnetic flux produced by the transformer windings.
  51. Hysteresis losses are the result of the molecules of the core material
    magnetized and de-magnetized.
  52. Copper losses are an additional transformer loss. They are due to the
    resistance of
    a transformer winding to the magnetizing current
  53. Oil in a transformer has two purposes:
    • • Insulating the transformer, and
    • • Cooling the transformer
  54. Oil functions to cool the windings and core of the transformer by a
    convection process
  55. The limiting temperature is ________ (winding) for modern transformers.
  56. The maximum top oil
    temperature is ______ for normal operation
  57. There are three general methods for
    increasing cooling rate seen in DWP transformers:
    • 1. Increase Surface Area of Tank.
    • 2. Increase the Rate of Air Movement.
    • 3. Increase the Rate of Oil Circulation
  58. FA  FOA   OA
    FA = Forced air

    FOA = Forced Oil Air

    OA = Oil Air aka convection cooled
  59. This type of bushing has a central conducting rod through which the
    conductor passes. Surrounding the rod is a series of insulating barriers
    held apart by spacers and enclosed in an oil filled porcelain skirt.
    Oil-Filled Bushings
  60. This bushing is similar to the Oil-filled except that the central rod is
    wound with alternating layers of insulation and tin foil.
    Condenser Bushing
  61. A typical instrument transformer ratio is ______
    400 to 1
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DS Buses