Main Generator Flashcards
What will cause the Q10/Q20 breakers to trip?
1) 86G1A or B actuation
2) CS to trip if 3-4 and 4-5 are open, or MPT disconnect open
3) Overcurrent
What components are actuated by the 86G1A (reverse power) relay?
Both output breakers open, exciter field breakers open, and UAT feed breakers open.
What is the purpose of the generator reverse power trip?
30 second time delay allows the operator to pick up load after synchronizing to grid.
Provides following functions for turbine trip:
-Allows time for steam to exit turbine to prevent turbine overspeed
-Provides 30 seconds for forced flow by the RCP’s during high decay heat period during LOOP
-Prevents RCP overspeed during a cold leg large break LOCA
Flowpath of current from the PMG to generator output.
PMG generates AC current that is fed the voltage regulators. The voltage regulators feed DC to the exciter. AC current is generated onto the rotor at the exciter. Rectified to DC on the rotor at the diode wheel. AC current is generated in the stator at 60 Hz 23.7KV
Main generator ratings
MVA 1361, MW 1224.9, V 25KV, 31,431 Amps, 4 poles, 0.9 PF
Q10/Q20 breaker closing causes:
- Auto start MPT fans
- Auto start 24 hour ground detection
- Permissive to start bus duct fans
Equations for power calculations
MVA=VA√3/1E6
MW=VA√3PF/1E6
MVAR=VA√3(sin0)/1E6
pf=Cos0
Main generator trips (21)
- diff current
- reverse power 30 sec
- loss of stator water cooling 45 seconds
- MPT differential
- MPT backup differential
- UAT differential
- Generator neutral ground
- Generator starting perior neutral ground protection
- Load rejection
- Generator low load trip <240MW and >62.5 Hz
- MPT sudden pressure
- UAT sudden pressure
- Loss of field
- Thrust bearing failure 70 psig immediate gen trip
- Over excitation
- UAT instant overcurrent
- Generator negative phase sequence
- Generator excitation trip
- Swyd lockout, 3-4, 4-5 and bus 4 lockout
- UAT neutral ground overcurrent
- Generator out of step
