Main Generator/EX2100 Flashcards
What are the underfrequency setpoints and the times associated with them? What happens when they are exceeded?
9776 and 4949 to help remember the setpoints
- 4 Hz for 3 minutes (alarm only)
- 9 Hz for 110 seconds – turbine trip (2 out of 2 logic)
- 4 Hz for 15 seconds – turbine trip (2 out of 2 logic)
- 9 hz for 2.4 seconds – turbine trip (2 out of 2 logic)
- For turbine trip to occur, both UF relays must detect the UF condition for the above time delays.
- For turbine trip function to be enabled, generator must be tied to the grid (either PCB closed)
- Main Turbine trips, EX2100 static exciter trips & Generator output breakers open
What are the generator limitations if Isophase Bus cooling is OOS?
Unit 2 - 14,000 amps
Unit 1 - 12,800 amps
Must be manually lowered to these values, no auto feature
What are the minimum and maximum allowed values with the 230kv and 500kv switchyards?
System voltage must be between 101.3% and 104.9%
230kv must not exceed 241.5kv
500kv must not exceed 525kv
As load is reduced with the voltage regulator in manual, what will happen? What action must be taken if in manual voltage control?
Per 34SO-N40-001-1/2
As load is decreased, the generator terminal voltage will increase. When voltage is reduced to compensate for this, care must be exercised to ensure the generator remains stable.
If Exciter must be operated in manual, station a licensed NPO @ P651 panel with no other duties, but to maintain and monitor the voltage level.
What is the danger associated with motoring the main generator?
Damage to the main turbine due to overheating from low steam flow
What is the difference between a simultaneous trip and a sequential trip? What type of failure will cause each?
Simultaneous trip: Usually caused by electrical faults or loss of stator water cooling
- Main Turbine trips
- EX2100 Static Exciter will trip
- Main Generator Output Breakers open
Sequential trip: usually caused by mechanical issues (most turbine trips)
- Trips output breakers after a Main Turbine trip after a time delay to ensure that driving steam is exhausted
- Breakers are tripped by the Reverse Power Relay (~ 3.75 sec)
- Designed to minimize the danger of main turbine overspeed
- ANY main turbine trip will cause a Sequential trip of the generator PCBs
- Opening of the generator output breakers prior to closure of the Main Turbine Stop Valves may result in overspeeding the turbine
- Failure of PCBs to open can cause motoring. Motoring of the generator can cause overheating of the turbine due to insufficient steam flow through the turbine
When does the EX2100 auto start during startup? What action must be taken if the correct response is not seen?
- The Exciter will Auto Start when Turbine Speed increases to about 95% (1710 rpm) – Regulator Control in AUTO
- If in Manual, must start the EX2100 on the HMI
- If Generator voltage does NOT increase immediately to 24KV, TRIP the Exciter Field Breaker (take EX2100 to stop)
How and where is the field applied in the main generator? Where is voltage induced?
- Brushes and collector rings apply the output of the EX2100 to the rotor. Brushes are spring loaded and ride on the collector rings.
- Rotor rotates, and develops the rotating magnetic field needed for generator action
- Stator windings (armature) house the stationary windings where the voltage is induced
Big picture - EX2100 -> Brushes and collector rings -> Rotating Rotor -> Stationary Stator -> 24kv voltage induced
What is done to MVARs prior to shutdown? At what turbine MWE is the turbine tripped?
On shutdown, MVARS taken to 0.
Once turbine is at 40-80 MWE, turbine is tripped
Where does the power to flash the field come from?
Field Flash:
R25-S146 via
Unit 2: 2R24-S005 (600 B)
Unit 1: 1R24-S019 (600 AA)
What is the difference between the Automatic Voltage Regulator (AVR) and the Manual Voltage Regulator (FVR)?
Automatic voltage regulator (AVR) regulates generator terminal voltage.
Manual voltage regulator (FVR) regulates generator field voltage.
