Step 7 written

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Step 7 written
2011-07-06 18:58:25
written exam step7

Journeyman exam review
Show Answers:

  1. What 5 things do you need to tell the Dispatcher about the situation?
    • Name.
    • Radio number.
    • Location.
    • Accident type.
    • Emergency need.
  2. State the proper procedure for safely connecting an ammeter into a circuit.
    Source voltage must be removed first, circuit is opened and ammeter is placed in series before re energizing and measuring, the ammeter must be placed on expected setting as well as placing the leads correctly, de energize source before removing ammeter.
  3. Why is it unsafe to connect ammeters directly across a voltage source?
    • Ammeters have very low resistance and will act as a short with the voltage source.
    • Fuse may blow, but potential for injury or meter damage still exists. Very large surges of current are capable of bursting insulation as well as causing super-heated blasts of plasma (electrically ionized gas).
  4. State at least 3 safety pracautions to be observed when using an ohmmeter.
    • De energize and discharge circuit before connecting leads.
    • Do not apply power while measuring.
    • If using an analog ohmmeter, the following also apply:
    • When finished measuring, switch to OFF position and remove leads. A standard ohmmeter supplies voltage when ON.
    • After changing ranges, adjust ohmmeter for zero, or infinity if using a shunt meter, before measuring.
  5. State at least 3 safety precautions to be observed when using a megger.
    • Do not touch leads while testing is in process.
    • Only use meggers for high resistance measurements, such as insulation.
    • De energize, isolate, and discharge circuit completely before connecting megger.
    • Discharge equipment after test, before handling leads or equipment.
    • Inspect leads before use.
  6. Identify Tacoma Power's control cable color code.
    • 1 black.
    • 2 white.
    • 3 red.
    • 4 green.
    • 5 orange.
    • 6 blue.
    • 7 white with black stripe.
    • 8 red with black stripe.
    • 9 green with black stripe.
  7. Identify 3 pieces of equipment with inputs or connections from a Potential Transformer.
    • Hot line indicator lamps.
    • M F P M.
    • Watt meters.
    • 21 or 59 relays ( 27 ) .
  8. Identify 3 pieces of equipment with inputs or connections from a Current Transformer.
    • Relays.
    • M F P M.
    • Watt meters.
    • Reclosers.
  9. State the purpose of a Bus Tie P C B in a transmission substation.
    • To use the bus tie for protection when taking a P C B out of service.
    • To tie the main and auxiliary busses together.
  10. State the precautions to be used whenever connecting or disconnecting batteries to a charger.
    Always energize the A C to the charger and adjust the voltage to minimize the potential differences between the charger and batteries before connecting.
  11. Substation battery chargers have an "Equilize" setting.
    State the purpose of this setting.
    • To burn sulfation from battery plates.
    • To reduce variations in cell voltage readings.
  12. What condition is needed to verify that a piece of equipment is isolated and ready for a clearance and grounding?
    • Visible open.
    • Red clearance tag.
  13. How are linear couplers different the current transformers?
    • A linear coupler follows the same safety rule as a P T: (should never be shorted).
    • The measured output is voltage rather than current.
    • A linear coupler has no iron core which gives it a faster responce time than a C T.
  14. Name 3 devices that can be controlled by SCADA.
    • Recloser (on or off ).
    • Load tap changer (raise or lower).
    • Breaker (trip or close).
    • Ground relay setting.
    • M O D's.
  15. Name 5 parameters that can be monitored with a
    Multi. Funtion. Panel. Meter.
    • Amps.
    • Volts.
    • VARs.
    • Watts.
    • Power Factor.
    • Frequency.
    • Volt amps.
    • Percent of load.
  16. What is the purpose of a battery eliminator in a battery charger?
    • It maintains a steady voltage for D C circuits in the absence of battery voltage.
    • Resists voltage spikes in the DC system.
  17. Name 2 applications where mechanical interlocks are used.
    • Station service & P T transformers.
    • Permanent shorts & grounds.
    • Capacitor banks.
    • 15 k v breakers. To avoid bus tie breakers being rolled into feeder cubicals and vice versa.
  18. Explain the difference between Wye and Delta transformer configurations relating to voltage and current values.
    • Wye transformers, both coil and line current are equal, phase voltage x 1.732 = line voltage.
    • Delta transformers, both coil and line voltage are equal, phase current x 1.732 = line current.
  19. What are the test parameters (time, voltage, per foot, etc.) for annual testing of fiberglass hot sticks at Tacoma Power?
    75,000 Volts per foot. for 1 minute.
  20. Identify the three different classes of rubber gloves used at Tacoma Power and state the allowed working voltage for each.
    • Class 0 0 (RED). 500 Volts
    • Class 0 (YELLOW). 1,000 Volts
    • Class 2 (BLACK). 5,000 Volts
  21. What are the test parameters (voltage, time, etc.) for testing each of the three classes of rubber gloves?
    • 0 0 (RED). 2,500 Volts for 2 & a half minutes.
    • 0 (YELLOW). 5,000 Volts for 2 & a half minutes.
    • 2 (BLACK). 20,000 Volts for 2 & a half minutes.
  22. List at least 3 different tests that check the integrity of the windings within a transformer.
    • T T R.
    • Transformer Ohm Meter.
    • Megger.
    • Power Factor test.
    • Excitation test.
    • Polarization Index, etc..
  23. Demonstrate the proper procedure to perform a T C G test. What is the purpose of this test?
    Test nitrogen space for combustible gases.
  24. What are the acceptable T C G test limits and actions to take for other levels of gasses?
    • Under 1 half percent. No indication of incipient fault.
    • .5 percent to 1 percent. Take periodic samples to establish trend.
    • 1 to 5 percent. Take immediate additional samples & prepare to investigate the cause.
    • Over 5 percent. Remove transformer from service.
  25. Demonstrate the proper procedure for dielectric breakdown field testing of in service oil from an O C B using both the D 877 & D 1816 testers. List the gap settings and acceptable tests limits for each.
    • A S T M, D 1816 .04 inch. gap, 20,000 Volts and above.
    • A T S M, D 877 .1 inch. gap, 25,000 Volts and above.
  26. State the purpose of the Neutralization Number test (D 974) and why this number is important.
    • Test for acid content of oil.
    • A low acid content is necessary to minimize electrical conduction and metal corrosion.
  27. What are the acceptable Neutralization Number test limits for a new sample of oil?
    D 974 .015 mg. K O H g and below.
  28. State the correlation between the Neutralization Number test and the Interfacial Tension test.
    An inverse correlation exists between a low N N and a higher I F T result. The I F T drops as acid increases and the N N rises.
  29. Under normal conditions, a job briefing can be a brief discussion of the job and hazards. What 2 factors call for a more extensive discussion?
    • If the work is complicated or particularly hazardous.
    • The Employees cannot be expected to recognize and avoid the hazards involved in the job.
  30. When a job briefing is conducted, what areas need to be covered as a minimum?
    • Hazards associated with the job.
    • Work procedures involved.
    • Special precautions.
    • Energy source controls.
    • Personal protective equipment, (PPE) requirements.
  31. On an O A, F A, F O A transformer, how does the type of cooling affect the MVA rating of the transformer?
    The more cooling provided for the transformer, the higher the rating of the transformer.
  32. Name 4 pieces of auxiliary equipment used with the oil processor.
    • Radiators.
    • Oil pump.
    • Heaters.
    • Cold traps.
    • Dry air machines.
    • Compressors.
    • Oil tankers and tanks.
  33. You already have your clearance. State the proper procedure for grounding a set of cables on a Magnefix in the Downtown Underground System.
    • Test the tester.
    • Install test cap on and test each phase.
    • Re test the tester.
    • Inspect shorts & grounds.
    • Attach the ground clamp end to groundwire.
    • Attach ground cap to hot stick.
    • Energetically apply ground with the other ground caps while staying clear of the ground caps.
  34. List working phase to phase & phase to ground clearances for the following nominal system voltages:
    • 4 K V, 12.5 K V, 13.8 K V, 2 feet 3 inches phase to phase. 2 feet 2 inches phase to ground.
    • 110 K V. 4 feet 3 inches phase to phase. 3 feet 2 inches phase to ground.
    • 230 K V. 7 feet 6 inches phase to phase. 5 feet 3 inches phase to ground.
  35. Identify the location of a no load tap changer. Identify and state the rated high side voltage for each tap position. Calculate the percent difference between each step.
    2.5% between each step
  36. Use the appropriate work practice or construction standard to answer:
    What wire sizes are used for the following types of circuits?
    • C T. Number 10.
    • Control. Number 12.
    • Status. Number 16.
  37. What is the P T (A C voltage) color code at Tacoma Power?
    • 1 (Black) Phase 2.
    • 2 (White) Phase 3.
    • 3 (Red) Phase 1.
    • 4 (Green) Ground.
  38. What is the C T (A C current) color code at Tacoma Power?
    • 1 (Black) Common.
    • 2 (White) Phase 2.
    • 3 (Red) Phase 1.
    • 4 (Green) Phase 3.
  39. List 5 pieces of information about a given cable that can be obtained from a cable list.
    • Origin.
    • Cable type & size.
    • Length.
    • Circuit type. (purpose).
    • Destination.
  40. Name the devices and give an example where each might be used in our system for the following device numbers:
    • 1. Master Element. Local breaker control switch.
    • 8. Control power disconnect. Breaker control power knife switch.
    • 21. Distance relay. Transmission line O C B.
    • 27. Undervoltage relay. Hot line indicator.
    • 43. Selector switch. Local or Remote switch.
  41. Name the devices and give an example where each might be used in our system for the following device numbers:
    • 49. Transformer thermal relay. Bank TRO (Trips feeder on transformer high temp).
    • 50. Instantaneous overcurrent relay. Feeder breaker.
    • 51. Time overcurrent relay. Feeder breaker.
    • 52. AC circuit breaker. O C B or S F 6.
    • 59. Overvoltage relay. Generation Substations.
  42. Name the devices and give an example where each might be used in our system for the following device numbers:
    • 62. Time delay. Feeder breaker Inst. trip (Delayed on close for cold load pickup).
    • 63. Pressure relay. Transformer sudden pressure.
    • 69. Permissive control device. SCADA on or off.
    • 72. DC circuit breaker. DC system.
    • 79. Reclosing relay. Feeder breaker.
  43. Name the devices and give an example where each might be used in our system for the following device numbers:
    • 81. Frequency relay. Generation Substations.
    • 86. Lockout relay. Sudden pressure trip.
    • 87. Differential relay. Bank or bus differential.
    • 90. Regulating device. Transformer voltage regulator.
    • 101. Breaker control. (remote). Control house
    • 201. Breaker control. (remote). SCADA.
  44. Name 5 items that can be checked by performing a T R X test on a circuit breaker.
    • Contact timing.
    • Stroke distance.
    • Over-travel.
    • Velocity.
    • Rebound.
    • Internal resistor.
    • Contact wipe.
  45. What is a bellcrank? Why is it used in circuit breakers?
    • Transmits force from one direction to another.
    • Used to transmit the closing force to the operating rod linkage.
  46. Describe the typical sequence of events that cause a power circuit breaker to close.
    • Closing coil operates.
    • Stored energy released to linkage and operating rod.
    • Operating rod moves contacts to closed position and charges opening spring.
    • Holding latch maintains contacts in closed position until released.
  47. Describe the typical sequence of events that enable a power circuit breaker to trip and open.
    • Trip coil or manual trip operates and releases trip latch.
    • Operating spring releases energy through linkage and operating rod, which seperates contacts.
  48. Identify a phantom load tester. What test (s) can be performed with this tester?
    • C T ratio testing.
    • C T connection testing.
    • Bus vibration and loose connection location.
  49. Identify a C T saturation tester. What test(s) can be performed with this tester?
    • C T ratio testing.
    • C T polarity testing.
    • C T saturation point.
  50. What tests are commonly performed on batteries and at what intervals?
    • Monthly. High & low cell voltage checks, overall voltage, charging current.
    • Quarterly. Every cell voltage check, overall voltage, charging current.
    • Annually. Impedance test (e bite) of each cell.
    • 3 to 5 years. Capacity test; frequency dependent on expected life of battery.
  51. Demonstrate the ability to switch a battery charger to the "equalize" setting. DO NOT leave the bank on equalize. Why is the "equalize" setting used?
    • To burn off sulfation from battery plates.
    • Reduces variations in cell voltage readings.
  52. A rectifier converts A C to D C or D C to A C?
    A C to D C.
  53. An inverter converts A C to D C or D C to A C?
    D C to A C.
  54. What solid state components are commonly used for rectifier and inverter conversions in our U P S systems & rectifiers?
    • A C to D C. S C R's or thyristors.
    • D C to A C. I G B T's (integrated gate-biased transistor).
  55. What are the 4 main stages of transformer processing and the purpose of each?
    • Heating the oil. Processing oil and heating the core temperature of the transformer.
    • Removing the oil. Storing the oil before applying vacuum to the tank.
    • Transformer dryout. Removes moisture from the transformer using heat and vacuum.
    • Vacuum filling. To prevent condensation in the transformer when refilling with oil.
  56. Explain wetting voltage.
    Voltage available at relay & status point contacts.
  57. Where would you find wetting voltage in a substation?
    • SCADA.
    • Some control, relaying systems.
  58. What type of relay(s) is (are) typically introduced to the relay protection scheme when replacing high side fuses is distribution substations with circuit breakers?
    • 63 Sudden pressure relay.
    • 81 Frequency relay.
    • 86 Lockout relay.
    • 50 51 High side Phase relays.
    • 50 51 N High side Phase relays.
  59. Explain what it means to "set up" a ground relay. When might this be done?
    Adjusting the relay settings to trip the breaker at a higher current value to avoid unnecessary trips due to imbalanced load.
  60. What is the difference in the protection relaying scheme for an underground feeder compared to an overhead feeder?
    • The 250 device. Instantaneous trip cutoff switch is added.
    • Recloser is permanently disabled or removed from scheme.
  61. Why is nitrogen used in a transformer?
    To keep a positive pressure in the transformer, to prevent air, water, and or foreign materials from entering the transformer.
  62. What is the purpose of the conservator?
    To allow for expansion and contraction of the oil in the transformer.
  63. Describe the purpose of the substation ground mat.
    • To provide a path for high current faults.
    • To eliminate step and touch potential.
  64. What is the minimum time that must elapse before capacitor bank, shorts & grounds are closed?
    5 minutes.
  65. What is the polarity of the majority of substation transformers used at Tacoma Power?
  66. What is the purpose of the Doble Power Factor testing?
    Measures the dielectric losses of the insulation.
  67. What is the purpose of the Dew Point Meter test on a high voltage S F 6 circuit breaker?
    Tests for moisture in the gas.