U2 Generator and Excitation Flashcards
What are the U2 Unit Differential (Unit HEA) Relay Actuations?
- 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 are the U2 Overall Differential (Overall HEA) Relay Actuations?
- Unit Differential
- Turbine Trip (33VED)
- Breaker Failure Relays
What does the Exciter do for the Generator?
- Exciter generates 3 phase 600v AC power that is applied to the stationary rectifiers
What does the Pilot Exciter do for the Generator?
- Supplies AC power to Voltage Regulator
- Produces excitation current for Main Exciter
What is the Exciter Field Brk interlock?
- Interlock prevents opening when either Generator Output Breaker is closed (A and A1 Bkrs)
- Cannot close the Exciter Field Bkr unless the Voltage Regulators are in manual
When is the Emergency Trip Pushbutton used to trip the Generator?
- When a motoring condition exists.
- ** Do not use if steam is being applied to the turbine, it can overspeed it
What is the Generator rotor create?
- Generator Field
If you have a Voltage Regulator Failure. what happens?
- If in-service channel fails, Voltage Regulator will transfer to other channel
- If auto control fails, Voltage Regulator will transfer to manual
What does the “Generator CBs Failure Trip” Pushbutton do?
- Isolates all downstream breakers of A1 and A2
- Will initially de-energize Transformer #4
- Designed to stop Main Generator from motoring upon failure of A1 or A2 to trip
How many generator H2 coolers are required for full load operation?
- all 4 coolers are required
if one is out, generator output is limited to 1000 MVA
Can you operation the generator if Generator seal oil is lost?
- No, you’ll have trip the generator and do emergency degas
What are the common Unit and Overall HEA actions?
- Turbine Trip
- Trip Exciter Field Breaker
- Turn excitation OFF
- Trip generator output breakers (A and A1)
- Fast Transfer from UAT to RAT
- Start time delay circuits for breaker failure
- Start sequence monitor and oscillograph
- Arms Main Transformer Deluge
- DCS input
- Enables shutdown of Main Transformer Cooling
What are the Unit HEA actions?
- Disables Main Generator Neutral Ground Relay
- Disables 26 KV Iso Phase Bus Neutral Ground
- Trips Stator Water Pumps
- Alarm “Unit Differential Operated”
What are the Overall Differential HEA actions?
- Alarm “Unit Overall Differential Operated”
- Alarm “Turbine Valve Overall Diff Trip” (IF 33 VED Turbine trip relay is energized)
What energizes the Turbine Trip Relay (33VED) in U2 with a 30 Sec delay?
- 4/4 Stop valves or Ctrl Valves closed with one of each pairs of Reheat Stop/Intercept valves AND - 4/4 Stop valves or Ctrl Valves closed or 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 energizes the Turbine Trip Relay (33VED) in U2 with no delay?
- 4/4 Stop valves or Ctrl Valves closed with one of each Reheat Stop/Intercept valves AND - ALL of the following: No RX Trip Bkrs open (P8) No SI Signal No Hi Hi SG Lvl (P14)
Is cold gas temp kept hotter or colder than Stator Water?
- Cold gas temp is kept 3-4°C colder than Stator Water to prevent condensation
What prevents an inadvertent loss of excitation at power if the exciter field breaker was opened?
- Generator breakers must be opened for the switch to open the exciter field breaker
What should an Operator be concerned with prior to pushing the Emergency Unit Trip pushbutton?
- Steam is isolated to the turbine to prevent a turbine overspeed
What conditions would allow an immediate generator trip upon a Turbine trip?
- A Turbine Trip occurs and the reactor trip breakers are closed and no SI or Hi-Hi SG level exists
What controls Generator voltage when the Automatic Voltage Regulator is in automatic?
- Generator terminal voltage sensed at the PT’s
What is the purpose of the V/Hz relay?
- Provide protection against overexcitation by actuation of an alarm and trip of the Overall HEA Differential relays.
What allows manual control of Turbine speed with the Speed & Load Changer?
- Turbine speed must be between 1790-1810 rpms and the Synch Selector switch must be in manual
How are the U2 rectifiers cooled?
- Natural Circ of Air
How are the U2 Output bushing cooled?
- Cooled by Stator Water
How is U2’s Exciter powered?
- By the Pilot Exciter (its a Permanent Magnet Generator (PMG))
- TBG-BE (alt)
What is the purpose of the thyrister converters on U2?
- it changes the output of the pilot exciter to D.C.
What is the flowpath of the U2 Main Generator?
- 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
