Main Generator - 1.0

Question 1

Generator Lockout Signals

Answer 1

Alterex Exciter Diff O/C (Regular)3
Generator (Phase) Diff O/C1 (Regular)
Generator O/C (Backup)
Generator Neg Phase Sequence (Regular)
Gen Reverse Power
Regular – 2.5 Sec w/ Turbine Trip
Backup – 30 Sec w/o Turbine Trip

Question 2

Generator Lockout Signals if output breaker is closed.

Answer 2

• Gen Loss of Field (Regular & Backup)*
• Gen Out of Step (Regular & Backup)*
• Gen Field Overvoltage (10 Sec TD) (Regular)
• Gen Field Overexcitation (Regular)

*Only armed during a voltage unbalance condition.

Question 3

Unit Lockout Signals

Answer 3

Unit Diff O/C (Regular & Backup)
Gen Neutral O/C (Regular & Backup)
Gen Neutral O/V (Backup Only – Shutdown Protection)*

*Both output breakers must be OPEN to activate.

Question 4

Unit Lockout Actions

Answer 4

Main Transformer Cooling Fans Trip
Stator Water Cooling Pumps Trip
Trip Gen Output Breaker (2-6 and 6-5)
Trip Exciter Field Breaker
Trips the Turbine
Initiates Breaker Failure Protection (2-6 and 6-5)
Overhead Alarms and Process Computer Alarms

Question 5

Generator Lockout Actions

Answer 5

Trip Gen Output Breaker (2-6 and 6-5)
Trip Exciter Field Breaker
Trips the Turbine
Initiates Breaker Failure Protection (2-6 and 6-5)
Overhead Alarms and Process Computer Alarms

Question 6

Main Generator Ratings:
A
Phase
RPM
Pole/60Hz
lagging pf
MVA
psig H2
KV
Excitation

Answer 6

3 Phase
1800 RPM
4 Pole/60Hz
.94 lagging pf
1373.1 MVA
75 psig H2
25 KV
530 VDC Excitation

Question 7

What is the concern for the generator regarding Reverse Power?

Answer 7

The concern of reverse power is not so much to protect the generator, but to protect the turbine from overheating of the exhaust hoods and high erosion rates of the last stage turbine blades.

Question 8

How long can the Isophase bus duct be operated at full load for?

Answer 8

30 mins

Question 9

Isophase fan start permissive:

Answer 9

1. Associated damper open.
2. Opposite damper closed.
3. Any start auto-opens TACS cooling supply (regardless of switch position).

Question 10

List and describe the kirk keys located on the Isophase panel.

Answer 10

1. GFBI key (Generator Field Breaker)
   
   • Ensure generator field breaker is open before 500KV Main gen disconnect is opened.
2. K12 Key
   
   • Ensures Main Generator ground disconnect is closed before isophase ground switch can be closed.

Question 11

Describe operation of the Isophase H2 Monitor meter.

Answer 11

0-100% scale reads 0-4%. Fails low on High H2.

Question 12

Isophase Heater operation.

Answer 12

Heaters cycle > 40% humidity when MG is S/D or unloaded.

Question 13

Describe the Generator Reactive Capability Curve and what components are of concern.

Answer 13

A-B: Too much reactive load causes rotor to overheat.
B-C: Too much real load causes stator to overheat.
C-D: Accepting to much capacitive load will cause stator core ends to overheat.