CE- Stator Cooling Water / Isophase Bus Duct Cooling Flashcards
What is the purpose of the Stator and Isophase cooling water systems?
To provide cooling for the main generator stator windings, generator bushings, the rectifier excitation system and the generator lower frame extension
Isophase bus cooling provides cooling for the electrical buses from the main generator terminals to the main power transformer and the Unit Aux Transformer
What is the cooling medium for the stator cooling water heat exchangers?
Turbine cooling
What system supplies makeup water to stator cooling system?
Demineralized Water
What system provides cooling to the collector housing heat exchanger?
Normal Chilled Water
What is the capacity of the Stator Cooling Water pumps? Power source? Location?
100% capacity pumps each 1000gpm, one running, one standby
NG
140’ turbine building, north east corner
What would cause the standby Stator Cooling Water Pump to auto start?
In-service pump’s discharge pressure decreases below its low discharge set point
What is the capacity of each Stator cooling cooler? What flows through the tubes of the cooler?
80% capacity
Turbine Cooling water
What is the purpose of the Stator Cooling Coolant Tank? Location? Capacity?
NPSH to pumps and surge volume
140’ Turbine Building, northeast corner
1070 gallons
What is the purpose of the stator cooling test valve? Where are the two test pushbuttons for the auto start of the CE standby pump and how do they work? Where is the valve located?
allows testing of the automatic sequence for the standby pump
Locally and in the Control Room
It simulates low pressure in the discharge line by opening a port to the storage tank
140’ turbine building below the stator cooling water storage tank
While the plant is operating, the in-service discharge pressure drops low enough to start the CE standby pump. Pressure is returned to normal. What is the status of the standby pump?
Still running, it will need to be secured manually
Unless there’s a turbine trip of course
What pressure is the stator cooling water being supplied to the main generator maintained at? In what position is the associated PCV locked?
60 psig
throttled
What temperature is stator cooling water maintained at prior to entering the generator inlet?
42C
How does the 3-way temperature control valve, TV-33, fail upon a loss of air?
Fails to the full cooling position
What is the cooling medium for the Isophase Bus Cooling Coils? What adjusts cooling flow rate? Location?
Turbine Cooling Water
cooler outlet valves
140’ turbine building
What is the capacity of the Isophase Cooling Air Blowers? What powers these blowers? Location?
100% capacity, both still operate at the same time however
NG
140’ turbine building
What cools the main generator collector housing? Where is the collector housing located? What cools the HX?
A fan, attached to the main shaft of the generator, circulates air over the heat exchanger and through the exciter unit by the fan due to turbine rotation
176’ Turbine Building, south side of the Main Generator
normal chilled water
(independent from the stator cooling and isophase bus duct cooling systems)
Where is the Stator Leak Monitoring System located?
At the Stator Cooling Water Skid
What is the purpose of the SLMS (stator leak monitor system)?
To identify a stator bar leak as early as possible while the generator is in operation to allow enough time to plan for repair during the next outage
(This is accomplished by monitoring the head tank vent for evidence of hydrogen)
minimize the possibility of low stator cooling water system oxygen
concentration by providing a means to inject air into the system head tank
What alarm signals are included on the new SLMS (stator leak monitor system) panel?
Hydrogen concentration >1.5%
Low air flow
Oxygen < 2ppm
What happens upon a loss of Stator Cooling? What is the purpose of the time delay for the generator trip?
Will cause a turbine and generator trip that will cause entry into the load rejection procedure.
The primary sensor for each trip initiates a 70 second time delay relay. When this relay is energized, the local and control room alarms are actuated. Unless the primary sensor returns to normal within the 70 second time frame, the turbine will trip
How long may rated current be maintained for upon a loss of Isophase Bus Cooling?
30 minutes
How does the CE system interface with IA?
system valve control
How does the CE system interface with NN?
powers the control and power instrumentation panel
How does the CE system interface with NG?
powers pump motors
In the CE system, what is powered by NK?
powers the local annunciator and generator trip relays
The CE water coolers are piped in series on the shell (stator water) side, and in parallel on the tube side (TC). Which side of the cooler is provided with valves for isolating a single cooler with the other still in-service?
Why is the shell side in series?
Where are the coolers located?
tube side (TC)
because they are only 80% capacity each
140’ turbine building, NE corner
Concerning the CE system, what is the purpose of the duplex strainer? Location?
to remove particulate material that might come from the outlet of the filter (in case of high filter D/P) and allow for strainer basket change out online in the event of a fouled strainer.
140’ turbine building, NE corner
What is the purpose of the CE stator cooling filters?
replaceable cotton wound cartridge filters
to clean the water before entering the main generator, which prevents arching
a third filter is upstream of the deionizer
generator inlet filter has a high D/P alarm at the local panel
In the CE system, what is the purpose of the deionizer?
maintains stator cooling water at a low electrical conductivity by continuous removal of ions
deionizer is in a bypass line that gets 10% of stator cooling water flow
Where are the CE filters and deionizer located?
140’ turbine building, NE corner
What is the purpose of the stator cooling flow control valve, FCV-12?
provides a manual means of coolant flow adjustment to the generator bushings
flow based on the percentage of total flow required by each section
In the stator cooling system, what does the new SLMS (stator leak monitor system) provide that the old one doesn’t?
analog signals to ERFDADS
digital alarms to the control room
In the CE system, what does oxygen do for the stator bars?
creates a corrosion resistant layer
a hydrogen leak into the stator bars prevents oxygen from getting to the stator bar surface
How much hydrogen permeates through the stator cooling insulating connections in the main generator? What is the flow path of the permeated hydrogen?
two to 3 cubic feet per day
gets into the stator cooling water and goes back to the coolant tank, then is vented to atmosphere through a vent line with an S-loop for condensed moisture drainage
air injection is provided from SLMS (stator leak monitor system) to minimize hydrogen in the tank
What happens when the Stator cooling and isophase bus duct cooling systems lose TC?
stator cooling temp will increase and trip the generator
isophase bus coolers will require a load reduction to maintain bus temp within limits.
What happens to the CE system when IA is lost?
stator cooling water system temperature control valve fails to the flow through coolers position
What happens to the CE system loses NN?
loss of local alarms
What happens to the CE system on a loss of NG?
loss of stator cooling pumps, generator trip
loss of isophase bus cooling blowers, load reduction
What happens in the CE system on a loss of NK?
loss of tripping power
