1st Plant Term Q's

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1st Plant Term Q's
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2012-11-27 11:40:02
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  1. What is the purpose of the Bulk Electric System in BC?
    The purpose of the BES is to get the power from the large generating stations to the load centers in the Lower Mainland and Vancouver Island.
  2. What are the primary voltages of the Bulk Electric System in BC?
    The primary voltages in the BES system are 500kV and 230kV.
  3. What two main river systems are home to hydro-electric generation facilities that make up 60% of BC Hydro’s generation portfolio?
    The Columbia and the Peace rivers
  4. Where is the bulk of the Load in BC Hydro’s system?
    Lower Mainland and Vancouver Island
  5. How many regions is the BC Hydro system divided up into with regards to generating facilities?
    There are 5 regions for generation. They are: Peace Region, Columbia Region, Lower Mainland and North Coast and Vancouver Island
  6. On what two basins is 80% of the BC Hydro generation portfolio served from?
    The Peace and Columbia basins
  7. What is an IPP?
    Independent Power Producer
  8. At what two basis voltage levels are IPPs interconnected into the provincial grid?
    IPPs are connected to the electrical grid at either distribution or transmission levels
  9. Under what type of agreement to IPPs sell the energy they produce back to BC Hydro?
    EPA’s or Electricity Purchase Agreements
  10. Approximately how much of BC Hydro’s generation portfolio is made up of IPPs?
    3000MW of IPP is equal to 26% of the 11,500MW total system generation
  11. What is the Plant Operator responsible for? Ensure your answer discusses both Operating Responsibility and Operating Authority.
    The Plant Operator is responsible for working together with the GC for reliability of the system and also to monitor the environmental conditions. To accomplish this the Plant Operator has Operating Responsibility over all water conveyance equipment, generating equipment under WPP < 100MW and dispatchable IPPs. The Plant Operator has no Operating Authority
  12. What is the Generation Coordinator responsible for? Ensure your answer discusses both Operating Responsibility and Operating Authority
    The GC is responsible for the reliability of the system and AGC. To accomplish this the GC has Operating Responsibility over all generation equipment under WPP = or > 100MW and IPPs above 100MW in BC Hydro balancing authority
  13. What is the PSOSE responsible for?
    PSOSE is responsible for overall operation of the power plants from an economic view.
  14. What is does the term “head” mean?
    Head is the pressure caused by the difference in height between the reservoir and the tailrace
  15. What are the two principal types of dam construction?
    • Earth-fill dam
    • Concrete dam
  16. T or F – a powerhouse must be built integral to a dam
    False
  17. Describe a storage type dam?
    A storage type dam has a large reservoir that stores the access runoff from snowmelt and also excessive rainfall. This storage can then be used in low water or rainfall times to generate power
  18. Describe a run-of-the-river type dam?
    A run-of-the-river type dam has a very small or no reservoir and is limited in its ability based on the river flow. These types of dams may not be able to run based on river flows, so can be an issue in drought situations.
  19. Describe a diversion type dam?
    A diversion type dam diverts water from a river or a stream towards a generating facility. These types of dams can have high environmental impacts and usually have special operations due to these environmental concerns.
  20. What is a reservoir?
    The reservoir is the holding bay for the dam. It is where the water will collect and feed the water to the intakes to the penstocks
  21. What is a tailrace?
    The tailrace is the body of water where the water exits the generators and continues to flow down the river
  22. What is does the term Power Release Facility mean?
    A Power Release Facility is the general term for all equipment used in generation at a hydro-electric generator.
  23. What is does the term Non-Power Release Facility mean?
    A Non-Power Release Facility is the general term for all equipment used to move water through or around a dam and are not generation related.
  24. What is does the term Non-Power Release Facility mean?
    A Non-Power Release Facility is the general term for all equipment used to move water through or around a dam and are not generation related.
  25. What is purpose of the “Headworks” at a hydro-electric generating station?
    The “Headworks” is used to control the water flow at the dam this being either through the generators or bypassing the generators via spillways.
  26. What components typically make up the “Intake” portion of the “Headworks”?
    • Spillway
    • Intake Structure, including:
    • -Trashrack
    • -Intake Maintenance Gate
    • -Intake Operating Gate
    • -Bubblers
    • -Surge Tower
    • -Penstock
    • -Scroll Case
    • -Stay Vanes
    • -Wicket Gates
  27. Explain the purpose and function of the Trashrack.
    The purpose of the Trashrack is to prevent any large debris from entering the intake structure. It does this by catching large debris in a large metal type cage that allows water to pass through without allowing large objects through. It must be regularly cleaned and also has pressure differential sensors if there is a large build up that requires immediate removal
  28. Explain the purpose and function of the Intake Maintenance Gate.
    The purpose of the Intake Maintenance Gate is to be able to isolate the Intake Operating gate for maintenance. They are usually lowered into place via crane.
  29. Explain the purpose and function of the Intake Operating Gate.
    The purpose of the Intake Operating Gate is to control the flow of water into the penstocks and to allow the penstocks to slowly fill with water if they are empty. They are usually operated using a hydraulic hoist system.
  30. Explain the purpose and function of the Bubbler system.
    The purpose of the bubblers is to prevent the water in the intake structure from freezing in extreme cold conditions. They are a series of tubes with holes that allow compressed air to bubble to the surface.
  31. Explain the purpose and function of the Surge Tower.
    The purpose of the Surge Tower is to limit water hammer in the penstock. They function by being open to atmosphere and allowing the reflecting surge of water a path to escape
  32. Explain the purpose and function of the Penstock.
    The purpose of the Penstock is to move the water from the reservoir to the power house for generation. Its function is to turn the potential energy into kinetic energy.
  33. Explain the purpose and function of the Scroll Case.
    The purpose of the Scroll Case is to equalize the pressure that is passed to the turbine. It does this by spinning the water around in a complete circle.
  34. Explain the purpose and function of the Stay Vanes.
    The purpose of the Stay Vanes is to direct the water at a proper flow angle to the wicket gates. They are permanently welded in place.
  35. Explain the purpose and function of the Wicket Gates.
    The purpose of the Wicket Gates is to control the speed of the turbine itself and in turn controlling the output of the generator. They are controlled by hydraulics.
  36. Explain the purpose and function of the Draft Tube.
    The Draft Tube’s purpose is to give a pathway for the water to exit and also create a negative pressure that increases the efficiency of the turbine.
  37. How are Intake Maintenance Gates operated? Where is it installed in relation to the Intake Operating Gate?
    The Intake Maintenance gates are typically lowered in place by a crane. They are located between the Intake Operating Gates and the Trash Racks.
  38. How are Intake Operating Gates operated? Where is it installed in relation to the penstock?
    The Intake Operating Gates are operated via hydraulics. The Intake Operating Gate is installed between the Intake Maintenance Gate and the entrance to the penstock.
  39. Where is the Surge Tower typically located? What is a key installation criteria for the Surge Tower in relation to the Forebay?
    The Surge Tower is typically located at the top of the Penstock. The top of the Surge Tower must be higher than the water level in the Forebay.
  40. Why is the Scroll Case snail shaped?
    The scroll case is snail shaped to evenly distribute the water to the turbine and to equalize the water pressure
  41. How are Draft Tube Maintenance Gates operated? Where are they installed in relation to the draft tube?
    Draft Tube Maintenance Gates are operated from a gantry crane. They are installed between the Draft Tube and the Tailrace.
  42. What are the two main types of turbines? Describe the principle of operation of each.
    Impulse turbines - derive all rotational energy from the velocity of the water. No pressure difference between the inlet and outlet of the turbine blades

    Reaction turbines - derive rotational energy from velocity of the water and also a pressure drop across the turbine blades
  43. Which type of reaction type runner is used for medium head plants? Describe how it uses water to create rotational energy on the turbine shaft?
    The Francis runner is suitable for medium head plants. The water enters the runner from the side via wicket gates and contacts the turbine buckets which cause the runner to spin then leaves out the bottom via the Draft Tube.
  44. What are guide bearings for? Typically how many?
    They keep the rotating shaft in position. There are usually two in large hydro generators.

    Generator and Turbine Guide Bearing

    Both are lubricated by oil and water
  45. What are thrust bearings for?
    Support the weight of the the shaft
  46. What head can a Kaplan runner be used up to?
    up to 50m
  47. Which type of runner is good for medium head plants?
    The Francis runner
  48. Which type of runner is good for low head plants?
    The Kaplan runner
  49. Which type of runner is good for high head plants?
    The Pelton runner
  50. What is the basic function of a hydro-electric generator? Discuss the energy transfer process
    A generator turns mechanical energy into electrical energy. The generator uses the rotational energy from the spinning shaft to spin windings that are induced by direct current. This rotating magnetic field induces alternating current in the stator
  51. What type of machines does BC Hydro use for the majority of their energy production and why?
    BC Hydro uses large three phase AC synchronous generators because of they produce both reactive and active power
  52. What is the purpose of the DC being applied to the field coils on the rotor?
    The DC being applied creates the magnetic field that induces the voltage in the stator. DC is also used so that backup power can be used from DC batteries.
  53. What is the air gap in a generator?
    The air gap is the physical separation between the rotor poles and the stator.
  54. What are the two types of rotors? Which are used on hydro-electric generators and why?
    Cylindrical rotors

    Salient pole rotors are used in hydro-electric generators because of there orientation. They rotate about a vertical axis
  55. What formula represents the relationship between speed and frequency on a hydro-electric generating unit?
    • RPM = 120 x f/P
    • f = frequency 
    • P = # of poles
  56. In which component, the rotor or the stator, is the alternating current waveform induced?
    The AC waveform is produced in the stator.
  57. To get a 3 phase alternating current, the stator windings are spaced ___ degrees apart.
    120° apart
  58. What is the purpose of bearings in a hydro-electric generator?
    The purpose of the bearings in a hydro-electric generator is to allow the rotor to spin and remain in the proper position.
  59. What pump is used to supply lubricating oil between the thrust pad and collar during startups to prevent damage?
    The lift pump is used during startup
  60. What is the purpose of the raw water system?
    The raw water system is the main header that feeds the entire hydro-electric generating station from the reservoir

    Supplies the cooling water system and fire water systems.
  61. How is the cooling water header pressure regulated?
    The cooling water header pressure is regulated using a pressure regulating valve
  62. How is cooling water monitored at a hydro-electric generating station?
    Cooling water monitor cubicles monitor the water flows and cooling water valve failures.
  63. What is the purpose unit circuit breaker?
    The purpose of the unit circuit breaker is for protection and to synchronize the generator to the rest of the BES (Bulk Electrical System)
  64. What is the purpose of the step-up transformer in the generating station?
    The purpose of the step-up transformers is to step the generator voltage up to a BES transmission voltage 500kV or 230kV
  65. What is the purpose of the generator isolation disconnect?
    The purpose of the generator isolation disconnect is to isolate the generator for maintenance.
  66. What is the purpose of the iso-phase bus?
    The purpose of the iso-phase bus is to connect the output of the stator to the step-up transformer and ultimately the BES.
  67. What is the purpose of the synchronizing and protection VTs?
    The two VT’s are used for synchronizing and protection purposes.
  68. What is the purpose of the surge arresters?
    The purpose of the surge arresters is to protect the equipment from overvoltages by providing a path to ground
  69. What are the standard generating station service AC bus voltages in BC Hydro?
    120/208 V and 347/600 V
  70. Why do substations have DC station service?
    DC service is used because DC energy can be stored in batteries
  71. What is the purpose of the thrust and guide bearings in a hydro-electric generator?
    The thrust bearings are used to support the weight of the unit and the guide bearings are used to keep the rotational shaft in position.
  72. When does the lift pump start and when does it stop during both startups and shutdowns of hydro-electric units?
    For startup the lift pumps start before the wicked gates are opened and continues to run until the unit reaches 90% speed

    For shutdown the lift pump starts once the speed is lower that 90% and stays on until the unit reaches a complete stop. Note some units will remain on until the bearing surfaces have cooled.
  73. What is the purpose of the braking system? When does the braking system come on during a shutdown of a hydro-electric unit?
    The purpose of the breaking system is to stop the unit at low speeds preventing wear on the thrust bearing and to hold the unit in place when shutdown. The breaking system will turn on once the unit reaches a pre-set speed maybe 25% of operating speed
  74. What are the three main subsystems of a governor system? What is the purpose of each?
    • Control subsystem – uses readings, control algorithms and output controls to adjust the speed and power of the system
    •                   
    • Hydraulic subsystem – valves and servo motors that respond to the control subsystem commands to modify water flow through the wicket gates
    •                   
    • Hydraulic oil sub system – oil storage or reservoir for the hydraulic components in the system
  75. On what principle does the governor system operate?
    Governors work on hydraulic amplification
  76. What are the main governor types and what are the typical ways speed of the hydro-electric turbine is detected?
    Mechanical Governor – senses speed using a flyball on top of the generator shaft or driven by a flexible cable

    Electric-Mechanical – an electric motor drives the flyball unit

    Analog Electronic – No flyball but a PMG that provides a signal to a transducer

    Digital Electronic – They use voltage sensing or speed signal generator or a combination of both
  77. What is meant by Gate Position and what are the two ways it can be controlled?
    • Frequency Setter (15F) – When the unit is not synchronized to the system, speed can be varied by adjusting the 15F. This will open and close the wicket gates to increase or decrease the frequency
    •  
    • Power Setter (65P) – When the unit is synchronized to the system, speed can be adjusted by adjusting the 65P. This will open and close the wicket gates to increase or decrease the power output
  78. Can Actuator Lock be reset from the Control Room?
    No, the governor must be checked out first and issues corrected before automatic control can be restored.
  79. What is Actuator Lock Free?
    Actuator Lock Free is using the gate limit switches to control the position of the wicket gates. There is no governor action, but allows the control of the load on the generator from the Control Center.
  80. What is meant by Actuator Lock? What conditions put a governor into Actuator Lock?
    Actuator Lock is the loss of the governor control via failure. It still allows the generator to be run, but with no governing controls. A loss of PT source, failure of speed signal, removal of any one of the governor electronic modules (65MI), activation of the governor test switch (43GT) or loss of redundant power supply (sensed by 27BX relay) will put the governor into Actuator lock.
  81. The Automatic Voltage Regulator has two control modes, a 70V and a 90V. Which one is manual and what does this mean to the operator? If the unit was in automatic what would it mean to the operator?
    The 70V setting is manual controls and 90V is in automatic. If the voltage regulator is in manual then the operator has to chase the power factor, but if it is in automatic then the unit will adjust to the system load changes on its own.
  82. What are the three quantities that must be matched for synchronizing to take place? How is each accomplished for a hydro-electric generator to be synchronized?
    1. The voltage magnitudes – measuring the voltage of the generator and the system and making sure the voltage difference is generally no more than a few percent to close.

    2. The frequency of the voltages – typically the generator is run at a little higher frequency than the system before it is brought online to produce MWs in the synchronization rather than take MWs.

    3. The phase angle between the voltages – the phase angle must be as close to 0° as possible before synchronizing to avoid snapping the rotor of the generator into phase with the system.
  83. What is the consequence of not matching the voltage magnitude variable?
    A large Mvar flow that could cause voltage changes in the area and instability for the incoming generator or the other generators on the system
  84. What is the consequence of not matching the frequency variable?
    If the unit is running to slow or low frequency then it will have negative MWs when synchronized to the system. For that reason they are generally running slightly faster than the system to create MWs once connected.
  85. What is the consequence of not matching the phase angle variable?
    If the phase angle isn’t matched as close to 0° as possible, the rotor of the generator will snap to the position that the system is running. Not good for the generator.
  86. What is a synchroscope and how is it used?
    The synchroscope is used to manually synchronize the generators to the system. The operator manually controlling the generator would get the needle at the 12 o’clock position before closing the circuit breaker and connecting the generator to the system.
  87. What is a synch-check relay and why isn’t it used for generator synchronizing?
    A synch-check relay determines if the phase angle is within allowable limits, but it doesn’t provide indication of voltage magnitude, frequency or phase angle so it isn’t used for synchronizing.
  88. What is the difference between a generating station auto synchronizer and a transmission station synchronizer?
    • The generating station auto synchronizer will actually adjust the generator if the three values are not within allowable limits to get the generator to match the system before synching.
    •  
    • The transmission station synchronizer will check the three variables and close if they are within the allowable limits, but cannot correct them if they are not within these limits.
  89. What is AGC? What does AGC use as an indicator that generation and load are not in balance?
    AGC stands for Automatic Generation Control. The AGC system uses the frequency as an indicator that the system is out of balance. If there is too much load and not enough system power the frequency will be low. If the system is over generating a smaller load then the frequency will increase.
  90. What are the three control modes for AGC? Describe each.
    • -Constant Frequency Control: Only monitors frequency and adjusts the governors to return the frequency to 60Hz. Can only be used if the tie-lines to other Balancing Authorities are open.
    •  
    • - Constant Net Interchange Control: Only responds to actual interchange flows vs the scheduled flows through the tie lines. It doesn’t respond to frequency, so only used when there is no frequency indication.
    •  
    • - Tie-Line Bias Control: When in this control mode the system will adjust to both tie-line flow errors and frequency, but will not respond to another Balancing Authorities drop in frequency unless it is requested.
  91. What does ACE stand for?
    Area Control Error
  92. What mode does a unit have to be in to be started from either FVO or SIO?
    The unit control must be in auto and the unit in remote control
  93. All of BC Hydro hydro-electric generators are capable of running in generate mode. What other mode of operation are some generators capable of running in? Describe this mode of operation.
    The generators can also run in Synch-condense mode which essentially turns them into a motor rather than a generator. They are absorbing MWs from the system instead of producing them.
  94. What is the basic process for putting a shutdown unit into generate mode?
    Once a successful start sequence and synchronization to the system is complete the generator is in “generate” mode.
  95. What is meant by the term “prohibited zones”? Explain by defining the various types of “prohibited zones”.
    The prohibited zones are rough load zones which are high vibration zones and high cavitation zones.
  96. All of BC Hydro hydro-electric generators are capable of running in generate mode. What other mode of operation are some generators capable of running in? Describe this mode of operation.
    The generators can also run in Synch-condense mode which essentially turns them into a motor rather than a generator. They are absorbing MWs from the system instead of producing them.
  97. What is meant by the term “prohibited zones”? Explain by defining the various types of “prohibited zones”.
    The prohibited zones are rough load zones which are high vibration zones and high cavitation zones.
  98. What is cavitation?
    Cavitation is the explosion of empty cavities in a liquid and is caused by rapid changes in pressure.
  99. What is meant by the “torque angle” of a hydro-electric generator?
    The torque angle of a synchronous machine is defined as the angular separation between the rotor and stator’s rotating magnetic fields.
  100. What is the 65P of a hydro-electric unit used for?
    It is used to adjust the torque angle of the generator. A negative torque angle will create synchronous condenser and positive torque angle will produce active power. These are used to respond to load changes within the system if connected to the AGC.
  101. What effect does varying the excitation have on the strength of the field on the rotor? What does varying the field do the MVars the unit is producing or absorbing? What net effect does this have on the terminal voltage of the machine and the station bus voltage?
    • Varying the excitation voltage will vary the excitation current flow, which will lead to a stronger generator voltage. Varying the field only has an effect on the MVars the unit is producing or absorbing if it’s varying the torque angle of the field.
    •  
    • If the terminal voltage or bus voltage starts to drop the excitation can be increased to produce more voltage and the opposite if the terminal voltage or bus voltage starts to increase the excitation can be decreased to lower the voltage.
  102. What is meant by the term “synchronous condense” mode?
    Synchronous condense mode is when the generator is running as a motor, or with negative torque, or ultimately taking VARs from the system.
  103. What is the reason for admitting compressed air into the draft tube during synchronous condense mode operation?
    To remove the water and allow the unit to spin in air instead of churning the water. It doesn’t take as many MW’s from the system spinning in air.
  104. Do the MVars have to be taken off a generator before it can be put in synchronous condense mode?
    No the unit remains connected to the system so no need to remove all MVars
  105. What is the only thermal plant operated remotely from FVO or SIO?
    Rupert Gas Turbine
  106. What are the two main reasons RPG is run?
    1. If Prince Rupert area has an outage, loss of 2L101 then RPG is required to blackstart and supply the area

    2. If 2L101 or another facility is OOS which may require the plant at some loading.
  107. What is the remote startup procedure for starting a RPG unit on Gas Mode?
    • -       The Plant Operator selects desired mode and fuel and confirm a “Ready to Start” prior to initiating start.
    • -       Prior to running in Gas Mode Spectra Energy must be contacted to ensure gas availability
    • -       Press the automatic start
  108. What are the special procedures for Blackstart of RPG units?
    There is a 5 minute time period once the unit reaches 60Hz to when the unit breaker must be closed to restore station service. The unit will trip if the AC station service is not restored within this time.

    In Blackstart situations, air supply is limited to 5 unit start attempts and battery capacity is about 3 hours.
  109. Can RPG units be run in synch condense? If so, what is the procedure to transfer RPG units into condense? What is the procedure for transferring RPG units from condense into generate?
    • Yes the RPG units may be used for synch condense. Once the unit is online as a generator the mode is changed from generate to condense and the turbine shuts down automatically.
    •  
    • To transfer from condense to generate the unit must be fully shutdown and then wait 15 min before starting the unit back up.
  110. What is the start sequence for a generator?
    • - The field breaker will close if open
    • - Release brakes
    • - Cooling Water valve open
    • - Lift pump start
    • - Brake pads clear, cooling valve 100% and lift pump at operating oil pressure, then the Governor Shutdown Control Supervision will pick up
    • - Release gate locks
    • - When both Gate Locks are clear the Governor Shutdown Solenoid will pick up
    • - The Gate Limit will rise to 20% and the Wicket Gates will open to "Breakaway Speed"
    • - At a predetermined speed the Speed-No-Load Solenoid will pick up to limit the wicket gate opening to the speed-no-load position (approximately 15%)
    • - At a predetermined speed in which a sufficient oil film has been established in the thrust bearing, the Lift Pump will shut down

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