U1 & U2 Generator and Excitation Flashcards
What causes the U1 Generator Unit Differential (Unit HEA) to roll?
- 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
What does the U1 Generator Overall Differential (Overall HEA) Trip?
- Turbine Trip (33VED)
- Breaker Failure Relays (trips other yard bkrs)
- Reverse power (Gen Motoring U1)
What does the Main Exciter do?
- Generates 3-phase 600v AC that is applied to the stationary rectifiers
What has to be done prior to closing the Exciter Field Breaker on U1?
- Voltage Regulators must be in Manual prior to closing
- Both O and O1 output breakers must be open for Exciter Field Bkr to open
Will the Exciter Field Breaker open with the Gen Output breakers closed?
- No, it will not
How do you close the Exciter Field Breaker?
- Switch must be held in closed until the Exciter Field Breaker is completely closed (Manual only, no automatic closures)
How are the output bushing cooled in U1?
- By generator gas (H2)
What are the 33 VED (Turbine Trip Relay) actuation signals with a 30 sec delay?
- 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)
What does 33 VED (Turbine Trip Relay) trip??
- Trips Overall HEA
What delays, if any, does the Unit differential (Unit HEA) relay have?
- 30 sec delay after a Rx trip
(allows RCPs to coast down to cool) - No delay for Transformer or Generator Trips
What delays, if any, does the Overall differential relay (Overall HEA) have?
- 30 sec delay after a Rx trip
(allows RCPs to coast down to cool) - No delay for Transformer or Generator Trips
What provides power to the Unit Diff Relay (Unit HEA)?
- 250v DC (Train B)
What provides power to the Overall Diff Relay (Overall HEA)?
- Switchyard 125 VDC
What provides power to 33 VED (Turbine Trip Relay)?
- 250v DC Train A
What is the H2 cooling flowpath?
- 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
What is MVARS in?
- capacitive / underexcited
What is MVARS out?
Inductive / overexcited
What can being underexcited cause?
- can cause slip of poles
How should the Generator Synchoscope rotating before closing the output breakers?
- slowly in the fast direction (Gen Frequency should be higher than Grid Frequency)
What do the Thyrister Converters do?
- Regulates the firing angle to change the voltage of field of the main exciter on U1
What is the main exciter powered by on Unit 1?
- 600v AC
Describe how the Voltage Regulator works in auto?
- controls terminal Voltage (using voltage droop)
Describe how the Voltage Regulator works in manual?
- controls when the SCR fires to control field Current
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.
- B. Unit Differential relays operate.
