Main generator excitation Flashcards
Power supplies to voltage regulators
- PMG
2. and 3. backups 133Z and 134Z
AVR Auto mode, what it does
Monitors generator PT and CT to control converter thyristor firing to control generator voltage. Internal PSS function dampens low frequency power oscillations.
AVR Manual mode
Maintains selected exciter field current regardless of grid fluctuations. Testing and emergencies only.
Functions of PMG
Supplies power to the AVR via Q07.
Backup power supply to DEHC
Redundant supply to turbine supervisory system
What cools the exciter?
Air circulated in housing cooled by WS.
When in auto, AVR maintains______, When in manual, the AVR controls ______
Generator voltage; Field current
The manual section of each channel tracks the auto section.
Make changes slowly when in manual because……
It is easier to overshoot when in manual and changes may take longer to fully manifest.
How will AVR respond to a grid voltage reduction?
AVR senses the voltage reduction and raises field current to attempt to improve grid stability. MVARS rise
What components can be controlled from control room
Excitation on/off Q10 and Q20
Voltage reg setpoint adjust
Swap between manual and auto with a white transfer light
excitation start stop switch in control room
Can be used to open q10 and q20 only if generator not connected to grid.
Generator ground detection
1 minute every 24 hours, ground alarm will latch and must be reset at AVR
Exciter ground detection
Monitors continuously, if clear does not latch in.
When in Auto control, limiters are….
Under excitation
V/Hz
Min field
Max field
When in manual control, restrictors…..
PQ restrictor-MW/MVAR limit
V/Hz restrictor
What could happen if you reset an AVR fault with the unit online?
The AVR could trip off which would cause a generator, turbine and possibly a reactor trip.
