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RO34 - Revised and Upgraded Decks > Generator and Excitation > Flashcards

Generator and Excitation Flashcards

1
Q

What causes Generator Unit Differential (Unit HEA) to roll?

A
  • **Emergency Trip Pushbutton **
  • Loss of Stator Cooling Water
  • 26KV Bus Duct Ground Fault (Backfeed)
  • Generator Differential
  • Generator Ground
  • Generator Overcurrent During Startup
  • Exciter Differential
  • Exciter Field Breaker Open
  • Main Transformer Differential
  • Main Transformer Sudden Pressure
  • UAT Differential
  • UAT Ground
  • UAT Sudden Pressure Trip
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2
Q

What causes the Generator Overall Differential (Overall HEA) to roll?

A
  • Turbine Trip (33VED)
  • Breaker Failure Relays (trips other yard bkrs)
  • Reverse power (Gen Motoring U1)
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3
Q

What does the Main Exciter do?

A

Generates 3-phase 600v AC that is applied to the stationary rectifiers

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4
Q

What has to be done prior to closing the Exciter Field Breaker on U1?

A

Voltage Regulators must be in Manual prior to closing

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5
Q

What must be done to open the Exciter Field Breaker?

A

Gen Output breakers must be OPEN! (O and O1 breakers for Unit 1 and A and A1 Breakers for Unit 2)

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6
Q

How are the output bushing cooled in U1?

A

Generator Gas (Hydrogen)

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7
Q

What delays, if any, does the Unit differential (Unit HEA) relay have?

A
  • 30 sec delay after a Rx trip
    (allows RCPs to coast down to cool)
  • No delay for Transformer or Generator Trips
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8
Q

What provides power to the Unit Diff Relay (Unit HEA)?

A

250v DC (Train B)

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9
Q

What provides power to the Overall Diff Relay (Overall HEA)?

A

Switchyard 125 VDC

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10
Q

What provides power to 33 VED (Turbine Trip Relay)?

A

250v DC Train A

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11
Q

What is the H2 cooling flow path?

A

turbine and collector ends, gen rotor and stator core, hydrogen coolers

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12
Q

What is MVARS in?

A

capacitive / under-excited

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13
Q

What is MVARS out?

A

Inductive / over-excited

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14
Q

What can being underexcited cause?

A

slipping of poles

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15
Q

How should the Generator Synchoscope rotating before closing the output breakers? What does this mean?

A

Slowly in the fast direction.

Gen Frequency should be higher than Grid Frequency

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16
Q

How are the Generator Rectifiers cooled for both units?

A

Natural Circulation of Air

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17
Q

What do the Thyrister Converters do in Unit 1?

A

Regulate the firing angle to change the voltage of field of the main exciter

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18
Q

What does the H2 cool on the U1 Generator?

A

The rotor

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19
Q

If you lose the main generator excitation system on U1, will the U1 Main Generator trip?

A

Yes

The generator will lose excitation; the Unit HEA relays will be energized

20
Q

What is the Gen Conditon Monitor looking for in the generator?

A

Products of combustion

21
Q

What is the DIRECT action that occurs when the Emergency Unit Trip Pushbutton is depressed?

A

Unit Differential relays operate

22
Q

What has to be done prior to opening the Exciter Field Breaker?

A

Both generator output breakers must be open for Exciter Field Bkr to open

(O and O1 breakers for Unit 1 and A and A1 Breakers for Unit 2)

23
Q

What are the common Unit and Overall HEA Actions?

A
  • Turbine Trip
  • Trip Exciter Field Breaker
  • Turn excitation OFF
  • Trip generator output breakers
  • Fast Transfer from UAT to RAT
  • Start time delay circuits for breaker failure
  • Start sequence monitor and oscillograph
  • Arms Main Transformer Deluge
  • DCS input
  • Enables shutdown of Main Transformer Cooling
24
Q

What are the Unit HEA Actions?

A
  • Disables Main Generator - Neutral Ground Relay
  • Disables 26 KV Iso Phase Bus Neutral Ground
  • Trips Stator Water Pumps
  • Alarm “Unit Differential Operated”
25
Q

What is on TDB 11-5 (Main Gen Capability Curve)?

A

MVARS and H2 Pressure inputs

26
Q

If you have a channel fault on your voltage regulator, what will happen?

A

it will swap to standby channel

27
Q

If Voltage regulator system calls for swap to other channel or to Manual and the swap fails to occur, what happens?

A

In 2-3 secs, an Excitation Trip will occur

28
Q

What are the 33 VED (Turbine Trip Relay) actuation signals with no delay?

A

All 4 Main Turbine Stop Valves are closed, and At least one valve out of each of the Reheat Stop/Intercept Valve pairs is closed
AND
Trips Overall HEA

29
Q

When does the Unit and Overall HEA’s not have a 30 Sec delay?

A

on a transformer trip or generator trip

30
Q

What is the flow path of U1 Main Generator?

A

600v AC => Step Down Transformer (167v AC) => Exciter Field Bkrs => Voltage Regulators (v DC) => Slip Rings => Main Exciter (v AC) => Field Rectifiers (v DC) => Slip Rings => Main Gen (AC) => Main Transformer

31
Q

When in auto on the voltage regulator, the Unit 1 voltage regulator senses the output of what?

A

The Main Generator

32
Q

When is the Emergency Unit Trip Push Button Used to Trip the Generator?

A

When a motoring condition exists. Do not use if steam is being applied to the turbine, it can overspeed it

33
Q

Which Unit has the Pilot Exciter? What does it do?

A

Unit 2. It is a Permanent magnet
- Supplies AC power to Voltage Regulator
- Produces excitation current for Main Exciter

34
Q

What is the flow path for the Unit 2 Main Generator?

A

Pilot Exciter (600v AC) => Step Down Transformer (78v AC) => Exciter Field Bkrs => Voltage Regulators (v DC) => Slip Rings => Main Exciter (v AC) => Field Rectifiers (v DC) => Slip Rings => Main Gen (AC) => Main Transformer

35
Q

What do the Thyrister Converters do in Unit 2?

A

changes the output of the pilot exciter to DC

36
Q

How are the output bushing cooled in U2?

A

Stator Cooling Water

37
Q

What controls Generator voltage when the Automatic Voltage Regulator is in automatic?

A

Generator terminal voltage sensed at the PT’s

38
Q

What conditions would allow an immediate generator trip upon a Turbine trip?

A

A Turbine Trip occurs and the reactor trip breakers are closed and no SI or Hi-Hi SG level exists

39
Q

What prevents an inadvertent loss of excitation at power if the exciter field breaker was opened?

A

Generator breakers must be opened for the switch to open the exciter field breaker

40
Q

What is the typical temperature difference between cold gas and stator water? Why?

A

Stator Water temperature is usually 3-4°C warmer than Cold Gas temperature to prevent condensation

41
Q

Can you operation the generator if Generator seal oil is lost?

A

No, you’ll have trip the generator and do emergency degas

42
Q

What does the “Generator CBs Failure Trip” Push Button do?

A

Isolate all breakers downstream of the Generator Output Breakers. Designed to stop motoring if the Generator Output Breakers do not open

Unit 1 is worse than Unit 2 bc it kills Reserve Feed to Opposite Unit

43
Q

What creates the Generator Field?

A

The Rotor

44
Q

What is the Main Exciter powered by in each unit?

A

Unit 1 = 600 VAC ONLY
Unit 2 = Pilot Excitor (permanent Magnet Generator) and 600 VAC backup

45
Q

What’s the purpose of the V/Hz relay?

A

Provide protection against overexcitation by actuation of an alarm and trip of the Overall HEA Differential relays.

46
Q

What is the Unit Response if the exciter field breakers do open (magically) during normal power operation?

A

Generator will lose excitation and the Unit HEA relays will be energized.

RO34 - Revised and Upgraded Decks (84 decks)

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