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4706 > U1 & U2 Generator and Excitation > Flashcards

U1 & U2 Generator and Excitation Flashcards

1
Q

What causes the U1 Generator Unit Differential (Unit HEA) to roll?

A
  • Emergency Trip Pushbutton ***
  • Loss of Stator Cooling Water
  • 26KV Bus Duct Ground Fault (Backfeed)
  • Generator Differential
  • Generator Ground
  • Generator Overcurrent During Startup
  • Exciter Differential
  • Exciter Field Breaker Open
  • Main Transformer Differential
  • Main Transformer Sudden Pressure
  • UAT Differential
  • UAT Ground
  • UAT Sudden Pressure Trip
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2
Q

What does the U1 Generator Overall Differential (Overall HEA) Trip?

A
  • Turbine Trip (33VED)
  • Breaker Failure Relays (trips other yard bkrs)
  • Reverse power (Gen Motoring U1)
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3
Q

What does the Main Exciter do?

A
  • Generates 3-phase 600v AC that is applied to the stationary rectifiers
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4
Q

What has to be done prior to closing the Exciter Field Breaker on U1?

A
  • Voltage Regulators must be in Manual prior to closing
  • Both O and O1 output breakers must be open for Exciter Field Bkr to open
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5
Q

Will the Exciter Field Breaker open with the Gen Output breakers closed?

A
  • No, it will not
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6
Q

How do you close the Exciter Field Breaker?

A
  • Switch must be held in closed until the Exciter Field Breaker is completely closed (Manual only, no automatic closures)
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7
Q

How are the output bushing cooled in U1?

A
  • By generator gas (H2)
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8
Q

What are the 33 VED (Turbine Trip Relay) actuation signals with a 30 sec delay?

A
  • All 4 Main Turbine Stop Valves are closed, and At least one valve out of each of the Reheat Stop/Intercept Valve pairs is closed
    AND
  • 4/4 Stop valves closed
  • 2/3 EHC Oil # low 800#
    (C8) (Turbine Trip)
    or
  • Rx trip bkrs open
  • SI
  • P14 (Hi Hi SG lvl (67%) 2/3 on 1 SG)
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9
Q

What does 33 VED (Turbine Trip Relay) trip??

A
  • Trips Overall HEA
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10
Q

What delays, if any, does the Unit differential (Unit HEA) relay have?

A
  • 30 sec delay after a Rx trip
    (allows RCPs to coast down to cool)
  • No delay for Transformer or Generator Trips
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11
Q

What delays, if any, does the Overall differential relay (Overall HEA) have?

A
  • 30 sec delay after a Rx trip
    (allows RCPs to coast down to cool)
  • No delay for Transformer or Generator Trips
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12
Q

What provides power to the Unit Diff Relay (Unit HEA)?

A
  • 250v DC (Train B)
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13
Q

What provides power to the Overall Diff Relay (Overall HEA)?

A
  • Switchyard 125 VDC
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14
Q

What provides power to 33 VED (Turbine Trip Relay)?

A
  • 250v DC Train A
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15
Q

What is the H2 cooling flowpath?

A
  • Fans both ends –> Turbine and colector ends –> along rotor shaft and stator core –> through gaps –> vent holes –> back through center of rotor and stator —> coolers –> back to suction of the fan
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16
Q

What is MVARS in?

A
  • capacitive / underexcited
17
Q

What is MVARS out?

A

Inductive / overexcited

18
Q

What can being underexcited cause?

A
  • can cause slip of poles
19
Q

How should the Generator Synchoscope rotating before closing the output breakers?

A
  • slowly in the fast direction (Gen Frequency should be higher than Grid Frequency)
20
Q

What do the Thyrister Converters do?

A
  • Regulates the firing angle to change the voltage of field of the main exciter on U1
21
Q

What is the main exciter powered by on Unit 1?

A
  • 600v AC
22
Q

Describe how the Voltage Regulator works in auto?

A
  • controls terminal Voltage (using voltage droop)
23
Q

Describe how the Voltage Regulator works in manual?

A
  • controls when the SCR fires to control field Current
24
Q

All of the following actions will occur when the Emergency Unit Trip Pushbutton is depressed.

Which ONE of the following is the only DIRECT action that occurs when the pushbutton is depressed?

A. Main Turbine valves close.

B. Unit Differential relays operate.

C. Reactor Trip breakers open.

D. Main Generator Output breakers open.

A
  • B. Unit Differential relays operate.
25
Q

What has to be done prior to opening the Exciter Field Breaker on U1?

A
  • Both O and O1 output breakers must be open for Exciter Field Bkr to open
26
Q

What are the Unit HEA Actions?

A
  • Disables Main Generator - Neutral Ground Relay
  • Disables 26 KV Iso Phase Bus Neutral Ground
  • Trips Stator Water Pumps
  • Alarm “Unit Differential Operated”
27
Q

What are the Overall HEA Actions?

A
  • Alarm “Unit Overall Differential Operated”
  • Alarm “Turbine Valve Overall Diff Trip” (IF 33 VED Turbine trip relay is energized)
28
Q

What is on TDB 11-5 (Main Gen Capability Curve)?

A
  • MVARS and H2 Pressure inputs
29
Q

If you have a channel fault on your voltage regulator, what will happen?

A
  • it will swap to standby channel
30
Q

What are the 33 VED (Turbine Trip Relay) actuation signals with no delay?

A
  • All 4 Main Turbine Stop Valves are closed, and At least one valve out of each of the Reheat Stop/Intercept Valve pairs is closed
    AND
    All of the following:
  • No RX Trip bkrs are open (P-8)
  • No SI
  • No P-14 (hi-hi SG level)
31
Q

What is the flowpath of U1 Main Generator?

A

600v AC –> Step Down Transformer (167v AC) –> Exciter Field Bkrs –> Voltage Regulators (v DC) –> Slip Rings –> Main Exciter (v AC) –> Field Rectifiers (v DC) –> Slip Rings –> Main Gen (AC) –> Main Transformer

32
Q

When is the Emergency Trip Pushbutton used to trip the Generator?

A
  • When a motoring condition exists.
  • ** Do not use if steam is being applied to the turbine, it can overspeed it
33
Q

What is the purpose of the V/Hz relay?

A
  • Provide protection against overexcitation by actuation of an Alarm and Trip of the Overall HEA Differential relays.
34
Q

What allows manual control of the U2 Turbine speed with the Speed & Load Changer?

A

Turbine speed must be between 1790-1810 rpms and the Synch Selector switch must be in manual

35
Q

How are the U2 rectifiers cooled?

A
  • Natural Circ of Air
36
Q

How are the U2 Output bushing cooled?

A
  • Cooled by Stator Water
37
Q

How is U2’s Exciter powered?

A
  • by the Pilot Exciter (its A Permanent Magnet Generator (PMG))- TBG-be (alt)
38
Q

What is the purpose of the thyrister converters on U2?

A
  • it changes the Output of the Pilot Exciter to D.C.
39
Q

What is the flowpath of the U2 Main Generator?

A
  • Pilot Exciter (600v AC) –> Step Down Transformer (78v AC) –> Exciter Field Bkrs –> Voltage Regulators (v DC) –> Slip Rings –> Main Exciter (v AC) –> Field Rectifiers (v DC) –> Slip Rings –> Main Gen (AC) –> Main Transformer

4706 (7 decks)

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