Stator & Isophase Bus Cooling (CE) Flashcards
What is the purpose of these systems?
Stator Cooling: 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?
TC
What system supplies makeup water to stator cooling system?
DW
What system provides cooling to the collector housing heat exchanger?
WC
What is the capacity of the Stator Cooling Water pumps? Power source?
100% capacity pumps each
NG
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?
80% capacity
What flows through the tubes of the cooler?
TC
Where is the Stator Cooling Storage Tank located?
140’ Turbine Building
What is the capacity of the tank?
1070 gallons
What is the purpose of the deionizer?
Maintain low electrical conductivity by continuous removal of dissolve mineral salts
How much of the Stator Cooling Water flow stream is directed through the deionizer?
~ 10%
Where are the two test pushbuttons for the auto start of the standby pump?
Locally and in the Control Room
While the plant is operating, the in-service discharge pressure drops low enough to start the 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?
60 psig (the valve is locked in this throttle position)
What temperature is stator cooling water maintained at prior to entering the generator inlet?
42 C
How does the 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?
TC
What is the capacity of the Isophase Cooling Air Blowers?
100% capacity, both still operate at the same time however
What powers these blowers?
NG
What cools the collector housing?
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
Where is the Stator Leak Monitoring System located?
At the Stator Cooling Water Skid
What is the purpose of the SLMS?
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
What alarm signals are included on the new SLMS panel?
Hydrogen concentration >1.5%
Low air flow
Oxygen < 2ppm
What happens upon a loss of Stator Cooling?
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 min
