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Systems > Generator Hydrogen(GH) > Flashcards

Generator Hydrogen(GH) Flashcards

1
Q

What’re the Hydrogen Coolers used for ?

A

Removes heat from hydrogen after the hydrogen removes heat from rotor

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2
Q

What cooling water is used for hydrogen coolers ? How is cooling water regulated ?

A

-Cooled by turbine cooling water
-TC auto regulated by Generator Hydrogen Temperature

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3
Q

Why can hydrogen leak into the TC system ?

A

Generator Hydrogen is at a Higher pressure than TC, to prevent TC water from leaking into generator

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4
Q

How do we remove hydrogen that’s leaked into the TC system?

A

-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

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5
Q

What does the Hydrogen Dryer/ Moisture Remover used for ??

A

Removes moisture from hydrogen, that prevents oxidation & corrosion inside generator

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6
Q

What is the driving motive force that pushes hydrogen through Dryer Moisture Remover? What is used to absorb moisture inside of it ?

A

-Driving force is DP developed by shaft mounted fans in generator
-Has activated alumni drying agent that removes moisture

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7
Q

What color does the Dryer Moisture Remover alumina change when it absorbs moisture ?

A

It’s turns from Blue color to a Pink color

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8
Q

How does the reactivation process of the Dryer Moisture Remover work ?

A

-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

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9
Q

During reactivation of Dry Moisture Remover what must you establish first before turning heaters on ?

A

Must establish instrument air flow, or else you could damage crystals from heater

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10
Q

What is the Generator Hydrogen Mass Flow Meter used for ?

A

-Provides continuous monitoring on hydrogen leakage
-Eliminates need to perform monthly hydrogen pressure drop test

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11
Q

What does the flow meter do to monitor hydrogen leakage ? What alarms will flow meter alarm ?

A

-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

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12
Q

What parameters do the Hydrogen Control Cabinet provide?

A

-Generator Gas(casing) Pressure
-Generator Gas Analyzer
-Generator Fan DP(could be used to determine Hydrogen Purity)
-Generator Gas Temperature

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13
Q

What alarms does the Hydrogen Control Cabinet have ?

A

-Machine Gas Pressure High-Low
-Machine Gas Purity Low
-Machine Gas Temperature High
-Generator Casing Liquid Detector Full

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14
Q

What does the Generator Gas Analyzer do ?

A

-Monitor & provide real time indications of Hydrogen Purity
-Have to have high Hydrogen Purity to have high effective cooling & efficient operation of generator

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15
Q

What’re the 4 modes for the Generator Gas Analyzer ?

A

-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)

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16
Q

What is driving force for flow through the Generator Gas Analyzers ?

A

Accomplished by DP across analyzers

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17
Q

What drives flow though the Generator Gas Analyzers when the generator fans aren’t available?

A

-Generator shutdown flow is accomplished by vent path to atmosphere via 3-way valve

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18
Q

What’re the Analyzer Inlet& outlet Filter/Dryers used for ?

A

Absorbs moisture & will turn pink

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19
Q

What are the Generator Gas Monitoring used for ?

A

Core monitor detected byproducts of overheating in generator known as pyrolysate

20
Q

How does the core monitor work ?

A

-Ionizes gas by alpha radiation in ion chamber, which creates small current
-Current is amplified & displayed on front of core monitor

21
Q

What is the amplified signal adjusted to during normal operation ?

A

Produces 90%reading on core monitor during normal operation

22
Q

What does it mean when ion chamber signal decreases from 90% full ?

A

Signal Rate decreases dependent on extent of overheating within generator

23
Q

What does the GGMS controller do for the core monitor ?

A

Signal digitally sent GGMS Controller which monitors,displays, & stores ion chamber signal of core monitor

24
Q

What is the driving force for the flow unit the core monitor ?

A

The Generator Fan DP will drive the flow

25
Q

What does gas control system of the Core Monitor do ?

A

-Controls amount & direction of flow within core monitor
-Flow meter should be adjusted 50% flow

26
Q

What is the Core Monitor filter used for ? How does it indication overheating ?

A

-Normal operation filter is bypassed
-If current drops below 60%, filters will be aligned
-If Current increases to >75% then generator overheating is present

27
Q

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 ?

A

There will be a core monitor malfunction alarm

28
Q

What does pyrolysate collector do ?

A

-When generator overheating is validated, it’ll be aligned to take sample for 15 minutes

29
Q

What do we do with pyrolysate collectors sample ?

A

Sample will determine which components is overheating

30
Q

What does the Generator Hydrogen Liquid Detector do ?

A

It collects any liquid that has entered generator casing

31
Q

What liquids can enter generator casing ?

A

-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

32
Q

How does Generator Casing Liquid Detector work ? What happens if Liquid Detector doesn’t get drained ?

A

-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

33
Q

What happens when you have a high level alarm in the liquid detector ?

A

Must have prompt action to avoid shutdown

34
Q

What is the hydrogen pressure inside generator casing? What provide hydrogen flow throughout generator casing ?

A

-Pressurized at 75psig
-shaft mounted fans allows hydrogen flow throughout casing

35
Q

What is the hydrogen purity maintained at inside generator casing ?

A

99.9% pure

36
Q

What is the normal status of the Core Monitor & Pyrolysate during normal operations ?

A

-Core monitor maintained in service has 500SCFM & monitors overheating

-Pyrolysate maintained in standby condition, awaiting signal from core monitor

37
Q

What should the hydrogen purity not drop below ?

A

-Maintained above 75% upper explosive limit
-Purity should not fall below 90%

38
Q

What should happen if you can’t maintain 90% Hydrogen Purity ?

A

Actions should be taking by increasing hydrogen concentration

39
Q

What should happen if Hydrogen Purity cannot be maintained above 80%?

A

Generator should be shutdown & hydrogen must purge CO2 PRIOR to reaching 75% upper explosive limit

40
Q

What is the minimum hydrogen gas pressure is procedurally allowable inside main generator ?

A

30psig this ensure adequate density of gas for cooling generator

41
Q

What happens on a loss of NHN-M27 ?

A

Would remove ability to purge the main generator with CO2

42
Q

What happens to Generator Hydrogen in loss of NN ?

A

-Lose hydrogen Gas Analyzer
-Alarms on control cabinet will activate
-Dryer/moisture remover will not be able to reactively alumina crystals

43
Q

What happens to Fire Protection on Generator Hydrogen ?

A

Loss of FP prevents purging of Main Generator

44
Q

What happens to loss of service gases ?

A

-Would prevent hydrogen makeup and hydrogen generator casing pressure will slowly decrease

45
Q

What happens to Generator Hydrogen on loss of Instrument Air ?

A

Prevents ability to:
-Purge CO2 from Main Generator
-Pressurize Main Generator casing prior to startup

46
Q

What happens to Generator Hydrogen to loss of Main Generator Seal Oil ?

A

Loss of Seal Oil will allow leak from Main Generator Hydrogen Casing

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