Stator & Isophase Cooling Water Flashcards
What is the purpose of CE?
Stator cooling provides cooling for: main generator stator windings generator bushings rectifier excitation system generator lower frame extension Isophase bus cooling: independent cooling for electrical buses from main generator terminals to the main power transformer and aux transformer
What is the pump and heat exchanger configuration in the stator cooling system?
2- 100% capacity pumps in parallel
2 - coolers in series
What cools the stator cooling heat exchangers?
TC
How is TC run through the heat exchangers?
it is run in parallel so that TC can be isolated to one HX and the other still be in service.
Describe the Isophase cooling system.
motor driven fan, air to water HX, and an air plenum to force air cool the isophase bus.
two units with a common air plenum, both operating at the same time.
What supplies makeup water to the stator cooling system?
DW
What cools the collector housing heat exchanger?
WC
What will cause the standby stator cooling pump to trip?
the in service pump’s discharge pressure falling below its low discharge setpoint. There is 2/3 logic for this.
What are the power supplies for the stator cooling water pumps?
NG
What is the capacity of the stator water coolers?
Each is 80% capacity, so if TC is removed from one of the coolers, generator load must be reduced to at least 80%
How does the stator cooling water temp control valve fail?
through the cooler
What is the purpose of the stator cooling storage tank?
NPSH for the pumps & to compensate for variations in water volume due to temperature and the presence of gases in the water.
What does the deionizer do?
maintain stator cooling water at a low conductivity by continuous removal of dissolved mineral salts in the mixed bed deionizer. It continuously deionizes 10% of the stator cooling flow stream.
Where can the automatic function of the standby stator cooling water pump be tested from?
control room or at the local control panel.
What happens to a pump that was auto started if the original pump returns to service?
it will continue to run until it is manually shutdown and returned to standby
What pressure is stator cooling water supplied to the generator at and how is it controlled?
60 psig and it is controlled by using the pressure control valve PV-34 (normally locked throttled)
How is flow controlled to the generator bushings and rectifier excitation system?
manually using FCV-12 & FCv-13
What stator cooling water temperature does TV-33 maintain at the generator inlet?
42C
How is cooling flow to the isophase bus controlled?
manually by throttling the cooler outlet valve
Where are the isophase bus fans controlled from?
locally at the load center supply breakers (NG)
How is the main generator collector housing cooled?
by a fan attached to the main shaft of the generator that circulates are over a heat exchanger that has WC flowing through it and then through the exciter unit.
How does the stator leak monitoring system work?
it monitors the head tank vent for the presence of hydrogen.
What else does the SLMS system do?
it provides a method of increasing stator cooling water O2 level by allowing for air injection into the system head tank.
How long after a stator cooling water trouble alarm do you have to reset it or fix the problem before the turbine trips?
70 seconds.
What must be done if isophase bus cooling is lost?
normal 34,000 amps may be maintained for up to 30 minutes, but after that, you must reduce to 23,000 amps for the unit to be as self sustaining cooling.
