LOT 202.17 Main Generator / Exciter Flashcards
- LOT 202.17 MG / Exciter*
- *
What will cause a turbine lockout?
Blocked by Voltage Unbalance:
Underfrequency
Complete loss of field
General:
Reverse Power
Thrust Bearing Vibration (± 40 mil) [2/2]
Loss of field voltage (> 80% ) [30 sec TC]
Loss of field voltage (< 80%) [0.75 sec TC]
Will cause Turbine Trip, MG Bkr trip, Field Bkr trip, and VR trip
Note:
Voltage unbalance activates if a potential transformer is lost. (Lost instruments to accurately read generator parameters)
- LOT 202.17 MG / Exciter*
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What cools the main generator?
- Rotor:*
- *Hydrogen**
- Cooling and minimizes windage losses*
- Stator:*
- *Stator Cooling Water**
- Stator Coils, Main Lead/Neutral Bus Bushings, and Current Transformers*
- Exciter Housing:*
- *CL-ACW**
- Fans attached to rotor to circulate air*
- LOT 202.17 MG / Exciter*
- *
What are the admin limits for MVARs in (+pf) and MVARs out (-pf)?
- MVARS in:*
- *90 MVARs**
- Gen Limit is 100 MVARs in*
- MVARS out:*
- *450 MVARs**
- LOT 202.17 MG / Exciter*
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If 2 rectifier fuses on a single phase blow, what are your actions?
Shutdown the MG
Each phase consists of 2 capacitor fuses and 2 diode fuses
- LOT 202.17 MG / Exciter*
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What will cause a generator lockout?
Differential Trips:
Generator Differential
Gen → Iso Phase Differential
Grounds:**
Running Ground
Startup Ground
Overexcitation:
Gen OE (118%) [> 2 sec TC]
Gen OE (110%) [>45 sec TC]
Gen OE due to Voltage Regulator
Blocked by Voltage Unbalance:
Gen out of step
Gen Backup distance
Will cause MG Breaker Lockout
Gen Ground Overvoltage
Will cause MG Breaker Lockout
General:
Field Bkr closed on turbine trip
Gen Negative Phase Sequence
Will cause Turbine Trip, MG Bkr trip, Field Bkr trip, and VR trip
- Note:*
- For ground trips, the generator breaker must be shut.
- Voltage unbalance activates if a potential transformer is lost. (Lost instruments to accurately read generator parameters)
- LOT 202.17 MG / Exciter*
- *
What does the different lights on the generator status mean?
- Green:*
- *Off**
- Auto Regulator de-energized, Base Adjust on Service*
- Amber:*
- *Test**
- Auto Regulator energized with output to null meter*
- Red:*
- *On**
- Auto Regulator in service*
- LOT 202.17 MG / Exciter*
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What powers the EH control cabinet?
PMG
120 VAC 420 Hz
Note:
EH Control Cabinet located in EAB 35’ Relay Room
- LOT 202.17 MG / Exciter*
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What will happen on a UAT or Main XFMR lockout?
Turbine Trip
Gen Output breaker trip
Gen Field breaker trip
VR trip
- *Switchyard breakers lockout**
- (510/520 or 590/600)*
UAT → Aux Bus breakers lockout
Will also occur if MG breaker fails to open on demand.
- LOT 202.17 MG / Exciter*
- *
How is the generator monitored for overheating?
- *Generator Condition Monitor**
- Detects particulates in H2 when insulation overheats*
Condition Monitor: TGB 55’ N of Generator Pedestal
Alarm Panel: TGB 55’ Exciter Switchgear Room
- Note:*
- Alarm on CP007
- Different sections of generator painted with different paints so operator can determine which section is overheating based on different particulates in the air.
- LOT 202.17 MG / Exciter*
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What is the purpose of the null meter on CP007?
Ensures the base voltage is equal to the auto voltage regulator setting
If auto voltage regulator lost and null meter not zeroed, could result in a sudden over/underexcited condition if auto VR fails.
- LOT 202.17 MG / Exciter*
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What do the different lights on the ground detection relay mean?
- Amber:*
- *Test in progress**
- Red:*
- *Test Complete**
- White:*
- *Ground Detected**
Measures for grounds automatically once every 24 hrs when field CB closed.
Note:
Located on CP007
- LOT 202.17 MG / Exciter*
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Why are bearings #9 and #10 insulated from the generator housing?
- *Minimize eddy currents**
- Causes bearing damage*
Bearings support the rotor shaft and restrain generator torque.
