Generator Excitation

Question 1

What is the purpose of Generator Excitation System?

Answer 1

provides regulated excitation to the field windings while generator is operating which in turn controls the terminal voltage

Question 2

What is the power souce for the generator Ground Detector?

Answer 2

Instrument Bus

Question 3

What is the Generator Field Breaker?

Answer 3

Used to protect field components including main generator during a fault or overcurrent

Question 4

Where can the Generator Field Breaker be Controlled from?

Answer 4

MCR

Question 5

What powers the Gen. Field Breaker?

Answer 5

Control Power from AVR cabinet 125vdc 2A-2 (3A-2)

Question 6

When can the Gen Field Breaker be opened?

Answer 6

Output GCB or TR main Disconnect Open

AND

Feeder breakers from TR 21 to Bus 21, 22,23,and 24 ALL OPEN

Question 7

What interlock requirements are in place between the Gen Field Breaker and the Turning Gear?

Answer 7

Field Breaker must be racked in AND OPEN or RACKED TO TEST to start turning gear

Question 8

What actions exist when field breaker is closed?

Answer 8

Regulator supply breakers close
MPT Fans start
Permissive to close output GCBs
Alarm for bus duct blower if not running

Question 9

What happens on a trip of field breaker?

Answer 9

Rapid de-excitation circuit energizes to dissipate gen. field
REGULATOR SUPPLY BREAKERS TRIP AFTER 3 SECONDS (41A1/A2)

Question 10

What is the Alterrex?

Answer 10

Provides a current to main generator field windings that can be regulated to maintain designed generator output

Air cooled using Cooling from TBCCW

Question 11

How does Alterrex regulate Gen Output?

Answer 11

AC output regulated by controlling field excitation to maintain desired Main Gen Output

Question 12

What is the Field Rectifier?

Answer 12

Converts AC to DC for Main Generator Field.

Question 13

How Many field rectifiers are there? How many NEED to be in service at any given time?

Answer 13

4 rectifier assemblies.
One of the 4 can be taken OOS with generator at full load using 5 pole disconnect switch
A key interlock prevents taking more than one out of service at a time

Question 14

What cools the Generator Field Rectifier?

Answer 14

Stator Water Cooling

Question 15

What is the Generator Governor?

Answer 15

controls load set, if you take the switch to lower the load set starts reducing which will close the control valves and open the bypass valves

Question 16

What is the Voltage Regulator for the Generator?

Answer 16

AVR is used to regulate the output voltage of the main generator and compensate for changes in the real and reactive load using solid state circuitry

Question 17

How many channels does the AVR have?

Answer 17

2 - only need 1 other is redundant

Question 18

WHat is the power source for the AVR?

Answer 18

Channels powered from MCC 25-2, 26-4 (35-2/36-4)

BACKUP FEED FROM 2A-2

Question 19

For the AVR, how many kV is equivalent to MVARS?

Answer 19

1kV = 50 MVAR

Question 20

What happens upon AVR Channel Failure?

Answer 20

Normally in Auto 1, fails to auto 2, fails to manual 2, fails to manual 1

Question 21

How does manual AVR control work?

Answer 21

Set the exciter field current and teh system will maintain that setpoint

Question 22

How does AVR Automotatic Mode work?

Answer 22

Set the AC Generator voltage output and system maintains that by changing exciter field current to meet voltage output.

Question 23

What is a VAR Runback?

Answer 23

On a scram or turbine trip, VARs are reduced to 0 to ensure reverese power trip relays actuate

Question 24

What can Excessive or too low VARs cause?

Answer 24

Excessive VARs can cause heat buildup

Lo VARs can cause pole slippage

Question 25

If the Turbine Trips, what happens to the Generator?

Answer 25

It does not trip just because of Turbine Trip. Will trip on reverse power relays