EDE

Question 1

DESCRIBE the basic construction features of the generator portion of the emergency diesel generator unit, including voltage production and cooling

Answer 1

• Air cooled/self-ventilated via fan attached to shaft
• Rotating Field
• Stationary Armature

Question 2

STATE the continuous load rating for the diesel generator

Answer 2

6083kV

Question 3

STATE the function of the static exciter/voltage regulator (SEVR), and DESCRIBE its operation in both the manual and automatic modes

Answer 3

Provides field flash during D/G startup
Controls Generator output voltage by controlling amount of DC excitation supplied to field

AUTO
• Error signal = Generator Output Vs. Reference signal.
• Reference signal adjusted by operator via the automatic voltage control switch.
• Auto voltage control switch controls a motor operated rheostat
• Error signal provides a gating signal to bridge rectifier SCRs
• Gating signal controls magnitude of DC applied to field windings, which controls magnitude of AC output voltage

MANUAL
• Manual Voltage Control provides direct input to bridge rectifier gating control circuit
• Operator controls motor operated rheostat via the Manual Voltage control switch

Question 4

DESCRIBE the “tracking” feature of the manual voltage regulator, and how it is enabled

Answer 4

TRACK feature
• Manual motor operated rheostat automatically tracks (follows) the position of the Auto motor operated rheostat.
• Prevent voltage transient if regulator automatically shifts to manual

Question 5

STATE the function of the emergency power sequencer (EPS)

Answer 5

Automatically reenergizes Bus E5 and/or E6 during loss of off-site power conditions by:
Starting D/G
Closing D/G breaker
Sequentially starts required loads for safe shutdown and/or Safety Injection conditions
Sequential starting feature ensures D/G is not overloaded- voltage and frequency maintained

Question 6

LIST the three sets of conditions that can activate the EPS

Answer 6

1) bus voltage < 70% nominal with no power available from RAT source with no time delay or
2) 1.2 sec TD when power available from RAT source.
3) Bus voltage < 95% nominal with an SI signal present for 10 seconds

Question 7

STATE the interlock which must be satisfied to de-activate the EPS

Answer 7

Closing either UAT or RAT breaker de-actuates the EPS

Question 8

STATE the purpose of the EPS RMO relay

Answer 8

• trips and locks out UAT & RAT breakers for associated train.
• Prevents control room operator from manually starting pre-selected large loads while D/G is sequencing its loads.
• Prevents inadvertent D/G overload.
• Remote manual starting = manual starting from Main Control Board (MCB).

Question 9

LIST the four general conditions which will cause a diesel generator output breaker to automatically trip open

Answer 9

• DG shutdown signal
• Protective relay actuation
• Paralleled with the grid when an SI occurs
o Remote only
• Paralleled with grid, and previously closed UAT or RAT bkr trips open

Question 10

EXPLAIN the function of the RLA contacts in the closing and tripping circuits for the diesel generator output breakers

Answer 10

Actuated by SI
Prevents some D/G trips;
•	High D/G lube water temperature, 
•	High D/G lube oil temperature, 
•	86DB (also prevents bkr from opening)

Question 11

DESCRIBE the operation of the EPS during the following scenario for LOCAL emergency diesel generator operation
• LOP or LOP/SI
• SI Only
• LOP with Subsequent SI

Answer 11

• LOP or LOP/SI
- EPS actuates. EDG auto starts. Breaker does not auto close.
• SI Only
- EPS does not actuate. EDG does not start.
• LOP with Subsequent SI
- EPS remains at Step 0.

Question 12

DESCRIBE the operation of the EPS during the following scenario for MAINTENANCE emergency diesel generator operation
• LOP or LOP/SI
• SI Only
• LOP with subsequent SI

Answer 12

• EPS actuates. EDG does not auto start. Breaker does not auto close.
  • SI Only
• EPS does not actuate. EDG does not auto start. Breaker does not auto close.
  • LOP with subsequent SI
• EPS remains at Step 0.

Question 13

DESCRIBE the operation of the EPS during the following scenario for REMOTE emergency diesel generator operation
• LOP or LOP/SI
• SI only
• LOP with subsequent SI

Answer 13

• LOP or LOP/SI
- EPS actuates. EDG auto Starts. DG Bkr auto closes.
• SI only
- EPS does not actuate. EDG Auto starts. Bkr remains open.
• LOP with subsequent SI
- EPS goes back to Step 0. No previously running loads are shed. (except Cont Cooling Units, RA relay)

Question 14

STATE the source and DESCRIBE the importance of 125VDC power for the proper automatic operation of the emergency diesel generator and EPS

Answer 14

Vital 125 VDC (ultimately from busses 11A and 11B). Required for;
• Automatic D/G start/stop
• Automatic D/G breaker closing/opening
• Speed & load control during parallel operations.
• Automatic & manual voltage control (including flashing).