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Question 1

STATE the function of the Isophase Bus Duct Cooling System

Answer 1

• Provides forced air cooling flow to the isolated phase bus to increase its current carrying capability

Question 2

STATE the function of the following components:
• Isophase bus ducts
• cooling fans
• space heaters

Answer 2

Isophase bus ducts
•	Separate bus duct for the three electrical phases.
•	Bus duct network connects the following:
	Output bushings
	Neutral Bushings
	Generator breaker
	GSU	
	UAT’s
cooling fans
•	forces air through ducts
space heaters
•	Utilized to keep Isophase ductwork internal temperature above dew point to prevent condensation in the bus enclosure.

Question 3

DESCRIBE the airflow in the forced air portion of the Duct Cooling.

Answer 3

• Bus duct cooling fans supply air to the B phase (B blows).
• 1 fan in run and 1 in standby
• Directed to the generator and the GSUs
• Return air flow is via the A and C phases to a common inlet plenum.
• All of the neutral bushing housing supply air is vented to atmosphere via screens.
• The majority of the air flow returns to the fan suction

Question 4

In regards to the Isophase Bus Duct Cooling Water:
• STATE the source of cooling water.
• STATE all signals that will initiate cooling flow.

Answer 4

STATE the source of cooling water.
• SCCW
STATE all signals that will initiate cooling flow.
• >130°F energizes the solenoid operated flow control valve for the operating system.
• >190°F opens the flow control valve for the standby system. (also starts the standby fan)

Question 5

EXPLAIN how to start up and shutdown the Bus Duct Cooling System

Answer 5

• Per ON1039.09, Isophase Bus Duct Cooling System Operation

Question 6

EXPLAIN how to shift the Bus Duct Cooling Fans.

Answer 6

•	Operate equipment with approved procedures, clearances, or other documents as appropriate to maintain proper configuration control.
Basics
•	Start B
•	Verify B running
•	Place A CS in MAN
•	Place SS to B
•	Place B CS in AUTO
•	Verify B running
•	Stop A
•	Place A in AUTO

Question 7

STATE the function of the Core Monitor

Answer 7

• Provides an immediate warning of local overheating in the generator before extensive damage results.
• Monitors particulate contamination of the H2.

Question 8

DESCRIBE the sequence of filling and purging operations that would be required following a generator maintenance period to electrical production and back to generator maintenance following shutdown

Answer 8

• Generator is filled with H2 at power
• Once shutdown Generator is purged with CO2
• After CO2 purge is complete, we purge with air
• Once the generator is ready to go online, we purge the air with CO2 and then purge the CO2 with H2

Question 9

STATE how H2 gas is circulated through the generator during operation

Answer 9

• Radial-flow, centrifugal fans mounted on each end of the rotor circulate the H2 through the generator
• The H2 cools the stator by flowing through radial and axial passages in the stator core.
• The H2 cools the rotor by entering the end retaining rings and flowing along the subslots toward the center
• H2 exits rotor through radial slots and joins H2 flowing through stator.
• H2 flows through two duplex coolers (parallel) at each generator end (total of four).
• The coolers’ outlet H2 is pulled toward and into each fan inlet