Stator And Isophase Bus Cooling Flashcards
What does the isophase bus cooling system provide cooling for?
Electrical buses from the main gen terminals
Main power transformer
UAT
What does the stator cooling water provide cooling to?
Main gen stator windings
Gen bushings
Rectifier excitation system
Gen lower frame extension
Describe the stator cooling system flowpath.
2-100% capacity pumps in parallel, two coolers in series, tank, filter, generator.
What provides continuous purification for the stator cooling water?
Deionizer by means of a bypass line from the cooler outlet to the storage tank.
What flows through the tubes in the stator cooling water coolers?
Turbine cooling water.
What is the arrangement of the stator cooling water cooler?
Can be parallel or series.
Describe the flowpath of the isophase cooling system.
Motor driven fan, air to water HX, 2-100% redundant units, both are normally in service at the same time.
What provides power to the pump motors?
NG
What provides power to the local annunciator and generator trip relays?
NKN-M45
What is the makeup water source for stator cooling?
DW
What provides cooling water to the collector housing heat exchanger?
Normal chilled WC
Where are the stator cooling water pumps located?
140’ of the turbine building
What causes the standby stator cooling water pumps to auto start?
If the in service pump’s discharge pressure drops below a given set point.
Describe the capacity and quality of the stator cooling water pumps.
80% capacity, shell and tube HX,
In series on the shell (stator water) side and in parallel on the tube side.
Whay are the duplex strainers used?
Allows for switching out the clogged strainer while still maintaining operation
What is the purpose of the stator cooling water storage tank?
Mounted at a sufficient height to provide NPSH for the stator cooling water pumps.
Describe the stator cooling filters.
Replaceable cotton wound cartridge filters
Located at the generator inlet and rectifier inlet.
High dP alarms at the local panel.
Why does the stator cooling line have a deionizer?
Maintains low electrical conductivity by continuously deionizing 10% of stator cooling water flow stream.
Where are the stator cooling test valve control switches located?
Two push buttons, one in control room, one at local control panel.
Button contact must be maintained throughout test for it to occur.
How can the pumps running from auto start be stopped?
Must be stopped manually unless they are locked out by a generator trip.
How is the stator cooling water pressure control valve controlled?
It isn’t… It’s locked in a throttled position that maintains 60 psig.
How is the Stator cooling water temperature control valve controlled
Pneumatically operated 3-way valve at the outlet of stator water cooler B.
TV-33 controls bypass flow around stator cooling water HX to maintain 42*C
In what position does the stator cooling temperature control valve fail on loss of air signal?
Fails to the full cooling (no bypass) position
Describe the isophase bus cooling coils.
Air to water HX, multi row, multi fin,
What provides cooling water to the isophase bus cooling coils?
Turbine cooling.
Flow rate and cooling rate is controlled by MANUALLY adjusting the cooler outlet valve.
Where are the isophase bus cooling coils located
140’ turbine building
Describe the isophase cooling air blowers.
2-100% capacity,
Both normally in service but one can be removed for maintenance.
How are the isophase cooling air blowers started?
Locally by MANUALLY operated start/stop switches on the load center supply breakers.
Where are the isophase cooling air blowers located?
140’ turbine building
What is the power supply for the isophase cooling air blowers?
NG
How is the collector housing unit cooled?
It has it’s own HX.
1 HX that is cooled by a fan that is attached to the main shaft of the generator.
What is the purpose of the collector housing cooling HX?
Keeps the collector housing cool to prevent damage to the brushes.
WC tube side. Collector air outside.
What system is used to monitor for a stator leak?
Stator leak monitor system.
How does the slms detect a leak?
Monitors the tank vent for evidence of hydrogen.
How many stator cooling pumps are there and how many are normally in operation.
2-100% capacity, one in standby
Where is the stator cooler system normally operated from?
The control room.
Where is the hydrogen that is collected in the stator cooling water released to?
It is released into the the coolant tank where it is vented to atmosphere through a vent line that has an S-loop
What happens to the plant if a stator cooling primary sensor is actuated?
We have 70 seconds to return the sensor to normal or a turbine and generator trip will occur.
What happens if isophase bus cooling is lost?
We have thirty minutes of run time without causing permanent damage or weakening of the bus material.
What will happen to the stator cooling if TC is lost?
Stator cooling temperatures will increase until reaching a turbine generator trip.
What will happen to isophase bus cooling if TC is lost to both coolers?
Will require a load reduction to maintain temperatures within limits.
What happens if power is lost to both stator cooling water pumps?
Turbine generator trip.
