Generator Hydrogen(GH) Flashcards
What’re the Hydrogen Coolers used for ?
Removes heat from hydrogen after the hydrogen removes heat from rotor
What cooling water is used for hydrogen coolers ? How is cooling water regulated ?
-Cooled by turbine cooling water
-TC auto regulated by Generator Hydrogen Temperature
Why can hydrogen leak into the TC system ?
Generator Hydrogen is at a Higher pressure than TC, to prevent TC water from leaking into generator
How do we remove hydrogen that’s leaked into the TC system?
-Vents at the TC outlet of hydrogen coolers
-8 vents directed to a drainbox maintained at 2-5 drops per minute, allows hydrogen to vent off from TC
What does the Hydrogen Dryer/ Moisture Remover used for ??
Removes moisture from hydrogen, that prevents oxidation & corrosion inside generator
What is the driving motive force that pushes hydrogen through Dryer Moisture Remover? What is used to absorb moisture inside of it ?
-Driving force is DP developed by shaft mounted fans in generator
-Has activated alumni drying agent that removes moisture
What color does the Dryer Moisture Remover alumina change when it absorbs moisture ?
It’s turns from Blue color to a Pink color
How does the reactivation process of the Dryer Moisture Remover work ?
-Isolate from Generator
-Align to suction of seal oil system
-Align instrument air
-Energize heaters
-Reactivation is complete once alumina turns back to Blue color
During reactivation of Dry Moisture Remover what must you establish first before turning heaters on ?
Must establish instrument air flow, or else you could damage crystals from heater
What is the Generator Hydrogen Mass Flow Meter used for ?
-Provides continuous monitoring on hydrogen leakage
-Eliminates need to perform monthly hydrogen pressure drop test
What does the flow meter do to monitor hydrogen leakage ? What alarms will flow meter alarm ?
-It measure hydrogen makeup to the generator casing
-If more than normal makeup means there may be a hydrogen leak
-Hydrogen supply from Hydrogen Storage Tank to Generator is high will cause alarm
What parameters do the Hydrogen Control Cabinet provide?
-Generator Gas(casing) Pressure
-Generator Gas Analyzer
-Generator Fan DP(could be used to determine Hydrogen Purity)
-Generator Gas Temperature
What alarms does the Hydrogen Control Cabinet have ?
-Machine Gas Pressure High-Low
-Machine Gas Purity Low
-Machine Gas Temperature High
-Generator Casing Liquid Detector Full
What does the Generator Gas Analyzer do ?
-Monitor & provide real time indications of Hydrogen Purity
-Have to have high Hydrogen Purity to have high effective cooling & efficient operation of generator
What’re the 4 modes for the Generator Gas Analyzer ?
-Normal Mode H2 in air
-H2 in CO2 (purging H2 with CO2)
-Air in CO2(Purging CO2 with Air)
-H2 in CO2(Purging CO2 with H2)
What is driving force for flow through the Generator Gas Analyzers ?
Accomplished by DP across analyzers
What drives flow though the Generator Gas Analyzers when the generator fans aren’t available?
-Generator shutdown flow is accomplished by vent path to atmosphere via 3-way valve
What’re the Analyzer Inlet& outlet Filter/Dryers used for ?
Absorbs moisture & will turn pink
What are the Generator Gas Monitoring used for ?
Core monitor detected byproducts of overheating in generator known as pyrolysate
How does the core monitor work ?
-Ionizes gas by alpha radiation in ion chamber, which creates small current
-Current is amplified & displayed on front of core monitor
What is the amplified signal adjusted to during normal operation ?
Produces 90%reading on core monitor during normal operation
What does it mean when ion chamber signal decreases from 90% full ?
Signal Rate decreases dependent on extent of overheating within generator
What does the GGMS controller do for the core monitor ?
Signal digitally sent GGMS Controller which monitors,displays, & stores ion chamber signal of core monitor
What is the driving force for the flow unit the core monitor ?
The Generator Fan DP will drive the flow
What does gas control system of the Core Monitor do ?
-Controls amount & direction of flow within core monitor
-Flow meter should be adjusted 50% flow
What is the Core Monitor filter used for ? How does it indication overheating ?
-Normal operation filter is bypassed
-If current drops below 60%, filters will be aligned
-If Current increases to >75% then generator overheating is present
If you align filter when current drops below 60%, and current doesn’t go up after 2 minutes filter is in service what does that mean ?
There will be a core monitor malfunction alarm
What does pyrolysate collector do ?
-When generator overheating is validated, it’ll be aligned to take sample for 15 minutes
What do we do with pyrolysate collectors sample ?
Sample will determine which components is overheating
What does the Generator Hydrogen Liquid Detector do ?
It collects any liquid that has entered generator casing
What liquids can enter generator casing ?
-Water can enter casing from Generator Hydrogen Cooler Leak or Stator Winding leak
-Imperfect Seal Oil Deflectors
-Excessive Seal Oil Pressure
-Backup Seal Flow through Hydrogen Detraining Tank
How does Generator Casing Liquid Detector work ? What happens if Liquid Detector doesn’t get drained ?
-Pipe will fill up and once you can see liquid in sight glass it must be drained
-If not drained will actuate level detector actuates alarm
What happens when you have a high level alarm in the liquid detector ?
Must have prompt action to avoid shutdown
What is the hydrogen pressure inside generator casing? What provide hydrogen flow throughout generator casing ?
-Pressurized at 75psig
-shaft mounted fans allows hydrogen flow throughout casing
What is the hydrogen purity maintained at inside generator casing ?
99.9% pure
What is the normal status of the Core Monitor & Pyrolysate during normal operations ?
-Core monitor maintained in service has 500SCFM & monitors overheating
-Pyrolysate maintained in standby condition, awaiting signal from core monitor
What should the hydrogen purity not drop below ?
-Maintained above 75% upper explosive limit
-Purity should not fall below 90%
What should happen if you can’t maintain 90% Hydrogen Purity ?
Actions should be taking by increasing hydrogen concentration
What should happen if Hydrogen Purity cannot be maintained above 80%?
Generator should be shutdown & hydrogen must purge CO2 PRIOR to reaching 75% upper explosive limit
What is the minimum hydrogen gas pressure is procedurally allowable inside main generator ?
30psig this ensure adequate density of gas for cooling generator
What happens on a loss of NHN-M27 ?
Would remove ability to purge the main generator with CO2
What happens to Generator Hydrogen in loss of NN ?
-Lose hydrogen Gas Analyzer
-Alarms on control cabinet will activate
-Dryer/moisture remover will not be able to reactively alumina crystals
What happens to Fire Protection on Generator Hydrogen ?
Loss of FP prevents purging of Main Generator
What happens to loss of service gases ?
-Would prevent hydrogen makeup and hydrogen generator casing pressure will slowly decrease
What happens to Generator Hydrogen on loss of Instrument Air ?
Prevents ability to:
-Purge CO2 from Main Generator
-Pressurize Main Generator casing prior to startup
What happens to Generator Hydrogen to loss of Main Generator Seal Oil ?
Loss of Seal Oil will allow leak from Main Generator Hydrogen Casing
