Stator and Isophase Bus Cooling

Question 1

What is the purpose of the Stator and Isophase bus cooling systems?

Answer 1

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

Question 2

What is the cooling medium for the stator cooling water heat exchangers?

Answer 2

TC

Question 3

What system supplies makeup water to the stator cooling system?

Answer 3

Demin water DW

Question 4

What system provides cooling to the collector housing heat exchanger?

Answer 4

Normal chilled water (WC)

Question 5

What is the capacity of the Stator cooling water pumps and what are their power source?

Answer 5

100% capacity
NG

Question 6

What would cause the standby stator cooling water pump to auto start?

Answer 6

Running pump low discharge pressure

Question 7

What is the capacity of the stator cooling cooler?

Answer 7

80% capacity

Question 8

What flows thru the tubes of the cooler?

Answer 8

TC

Question 9

What is the capacity of the Stator cooling tank?

Answer 9

1070 gallons

Question 10

What is the purpose of the deionizer?

Answer 10

Maintain low conductivity by removing mineral salts

Question 11

How much stator cooling water flow is sent thru the deionizer?

Answer 11

10%

Question 12

Where are the 2 test push buttons for the auto start of the standby pump?

Answer 12

Locally and in the control room

Question 13

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?

Answer 13

Still running - it needs to be manually secured, unless there is a turbine trip

Question 14

what pressure is the stator cooling water being supplied to the main generator maintained at?

Answer 14

60psig (valve is locked in the throttled position)

Question 15

What temp is the stator cooling water maintained at prior to entering the generator inlet?

Answer 15

42C

Question 16

how does the temp control valve TV-33 fail upon loss of air?

Answer 16

Full cooling position

Question 17

What is the cooling medium for the isophase bus cooling coils?

Answer 17

TC

Question 18

What is the capacity of the isophase cooling air blowers?
What powers these blowers?

Answer 18

100% but both still run
NG

Question 19

What cools the collector housing?

Answer 19

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

Question 20

What is the purpose of the Stator leak monitoring system? (SLMS)

Answer 20

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

Question 21

What alarm signals are included on the new SLMS panel?

Answer 21

Hydrogen concentration greater than 2.5%

Low air flow

Oxygen less than 2ppm

Question 22

What happens upon a loss of stator cooling?

Answer 22

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.

Question 23

How long may rated current be maintained upon loss of isophase bus cooling?

Answer 23

30 mins