MAIN GENERATOR & EXCITER Flashcards
What happens if the generator field breaker is opened with either generator breaker closed?
The generator acts as an induction motor.
How long must the ISO phase bus duct cooling system be operated to reduce humidity?
For more than 24 hours.
What conditions must be met before opening ISO phase bus duct inspection hatches?
Generator breakers must be open, field breaker must be open, and cooling fans must be off.
What is the maximum generator current allowed if ISO phase bus duct cooling is unavailable?
Generator current must be reduced to less than 18,000 amps within 30 minutes.
In what mode should the voltage regulator always be when the generator is loaded?
AUTO mode.
What can happen if the generator is loaded with the voltage regulator in MANUAL mode?
Damage to the transformer can occur in less than 1 minute if the de-excitation circuit fails.
What components are cooled by the generator’s hydrogen cooling system?
Stator frame, rotor, and windings.
What is the synchronization procedure for the main generator breakers?
The first generator breaker can be closed manually when the synchroscope is within +/- 10 degrees in AUTO, and the second breaker must be in the SCOPE ON position to close.
What must be done before closing the second generator breaker during synchronization?
Place the synchroscope in the ON position.
What is the function of the exciter’s field flash?
It is powered by 1H (“A” DC) and located in the TB 322’ Switchgear Room.
What cools the exciter rectifier?
Stator coolant.
What does the AC voltage regulator maintain, and what can cause it to trip to MANUAL mode?
It maintains output voltage constant at 19kV. It trips to MANUAL mode due to:
1. Control switch operation
2. Loss of DC
3. Field breaker trip
4. Exciter field overcurrent
5. Max excitation limit
6. 19kV potential loss
7. Excessive volts per Hz.
What does the DC voltage regulator adjust?
It adjusts field strength to change terminal voltage.
What does the Under Excited Reactive Ampere Limit (URAL) prevent?
It prevents the main generator from falling out of synchronism (slipping poles) and ensures minimum excitation.
What happens to the Auto Voltage Regulator when the generator is on the URAL?
The Auto Voltage Regulator will NOT be responsive to commands to lower excitation.
What is the function of the De-Excitation Circuit?
It runs back voltage on the Alterrex (exciter) as a backup to the field breaker opening.
What does the 32 MT Reverse Power Relay do?
It sequentially trips with a 5-second time delay before opening the generator breaker to prevent turbine overspeed.
What conditions does the 32 MT Reverse Power Relay sense?
It senses reverse watt and ensures all steam sources are isolated.
What is the purpose of the 32P Anti-Motoring relay?
It acts as a backup to the 32MT, tripping the turbine and generator simultaneously with a 30-second time delay.
What happens if the generator is at low speed when the 32P Anti-Motoring relay trips?
The trip is immediate.
Why is the standby fan for bus duct cooling kept in PTL?
It is kept in PTL due to the manual damper.
How is a Gen Core Monitoring alarm validated?
By placing the filter in-service and observing it clear.
What actions are taken if a valid Gen Core Monitoring alarm persists?
Runback to 45%, trip the reactor after 5 minutes if still in alarm, and trip the turbine if power is less than 45%.
