Stator and Isophase Bus Cooling Flashcards
What is the purpose of the Stator and Isophase bus cooling systems?
Provide cooling to the main generator stator windings, generator bushings, 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 main transformer
What is the cooling medium for the stator cooling water heat exchangers?
TC
What system supplies makeup water to the stator cooling system?
Demin water DW
What system provides cooling to the collector housing heat exchanger?
Normal chilled water (WC)
What is the capacity of the Stator cooling water pumps and what are their power source?
100% capacity
NG
What would cause the standby stator cooling water pump to auto start?
Running pump low discharge pressure
What is the capacity of the stator cooling cooler?
80% capacity
What flows thru the tubes of the cooler?
TC
What is the capacity of the Stator cooling tank?
1070 gallons
What is the purpose of the deionizer?
Maintain low conductivity by removing mineral salts
How much stator cooling water flow is sent thru the deionizer?
10%
Where are the 2 test push buttons 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 needs to be manually secured, unless there is a turbine trip
what pressure is the stator cooling water being supplied to the main generator maintained at?
60psig (valve is locked in the throttled position)
What temp is the stator cooling water maintained at prior to entering the generator inlet?
42C
how does the temp control valve TV-33 fail upon loss of air?
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?
What powers these blowers?
100% but both still run
NG
What cools the collector housing?
A fan attached to the main shaft of the generator, circulates air over the heat exchanger and thru the exciter unit by the fan due to turbine rotation
What is the purpose of the Stator leak monitoring system? (SLMS)
To identify a stator bar leak ASAP while the generator is in operation to allow enough time to plan for repair during the next outage.
Monitors the head tank vent for evidence of hydrogen
What alarm signals are included on the new SLMS panel?
Hydrogen concentration greater than 2.5%
Low air flow
Oxygen less than 2ppm
What happens upon a loss of stator cooling?
Turbine and generator will trip and cause us to go into load rejection procedure
Initiates a 70 second time delay relay. When the relay is energized, the local and control room alarms are actuated. Unless the primary sensor returns to normal within 70 seconds the turbine will trip.
How long may rated current be maintained upon loss of isophase bus cooling?
30 mins
