Non-class 4.16kv Power(NB)

Question 1

Describe the purpose of the Non-Class 4.16kv POWER SYSTEM. (NB)

Answer 1

•The non-class 4.16kv power system steps down voltage from non-class 13.8kv buses(NAN-S01&2) to 4.16kv to supply power to:
•2 NON-class load groups
-NBN-S01 and NBNS02

•Also steps down voltage to 4.16kv from NAN-S03 and NAN-S04 to power:
•2 CLASS load groups
-PBA-S03 and PBB-S04

Question 2

How IS the power from the non-class 4.16kv system stepped down?

Answer 2

•2 normal system XFRM’s
-NBNX01 and NBNX02

•2 Engineered Safety Feature XFMR’s
-NBNX03 and NBNX04

•Two 4.16kv switch gear
-NBN-S01 and NBN-S02

Question 3

Describe the flow path of the Non-class 4.16kv power to the Unit Auxiliaries (house loads)

Answer 3

Power is supplied:
•FROM non-class 13.8kv, NAN-S01&S02

•Through normal service XFMR, NBNX01 and NBNX02

•TO the Non-class 4.16kv switchgear busses, NBN-S01&S02

Question 4

Describe the Alternate path of power if one of the NAN-S01 or S02 buses is down.

Answer 4

•A cross-tie on NBN-S01 will connect both NBN-S01 and NBN-S02 to feed each other from either NAN-S01 OR NAN-S02

•Cannot crosstie if both supply breakers from NAN-S01or NAN-S02 will be closed

Question 5

Describe the power path from Off-site to class 1E 4.16kv switchgear.

Answer 5

•From Start-up XFMR’s

•Through Non-class 13.8kv switchgear, NANS05&NAN-S06

•Then through Non-class 13.8kv switch gear, NAN-S03&S04

•Then through the ESF XFMR’s NBN-X01 and X02

•To the class 1E 4.16kv switchgear, PBA-S03 and PBB-S04

Question 6

Describe the power path during a loss of off-site power or a station blackout.

Answer 6

The Station Blackout Generator may be started and aligned to:
•The NAN-S03 switchgear
•Through the ESF XFMR.NBN-X03
•To Class 1E 4.16kv switchgear, PBA-S03(preferred) or PBB-S04(Alt)

Question 7

Describe the purpose of the Normal Service XFMR, NBN-X01 and NBN-X02.

Answer 7

•The purpose of the Normal Service XFMR is to step down non-class 13.8kv from the Generator to Non-class 4.16kv for distribution by NBN-S01& NBN-S02

Question 8

What are the isolations for the Normal Service XFMR’s?

Answer 8

•Both Normal Service XFMR’s have ONE isolation on both sides of it.

-Upstream on NAN-S01 & NAN-S02

-Downstream on NBN-S01 and NBN-S02

Question 9

What are the temperature indications on the ORIGINAL Normal Service XFMR NBN-X01 and NBN-X02 and ORIGINAL ESF XFMR NBN-X03 and NBN-X04

Answer 9

•It uses gauges to indicate temps
-Top Oil
&
-Winding temps (Starts cooling fans)
~Yellow indicator shows the temp in that exact moment
~ Red indicates the highest winding temp reached since last reset.
(Rest weekly during AO rounds)

Question 10

What starts the cooling fans on the ORIGINAL Normal Service XFMR and Engineered Safety Features XFMR.

Answer 10

•The winding temp gauge starts the cooling fans @ 70C

Question 11

Describe the purpose of the Non-class 4.16kv switchgear system?

Answer 11

•Consist of two buses NBN-S01 and NBN-S02
•Those two buses distribute 4.16kv power to non-safety related loads.

Question 12

Describe the characteristics of a NBN-S01 and NBN-S02 switchgear.

Answer 12

•Metal Clad
•Elec. operated, elec. racked
•Vertical lift
•Draw-out circuit breakers

-Equipped with:
•local operating controls
•Indicating lights
•meters
•Fuses

Question 13

What components does NBN-S01 power?

Answer 13

-4 Alpha’s
• ‘A’ Condensate pump(CD)
• ‘A’ Plant cooling water pump (PW)
• ‘A’ Turbine cooling water pump(TC)
• ‘A’ Nuclear cooling water pump(NC)

-3 Bravo’s
• ‘B’ condensate pump (CD)
• ‘B’ Heater drain tank pump (ED)
• ‘B’ normal chiller (WC)

Question 14

What components does NBN-S02 power?

Answer 14

• 3 Bravo’s
  • ‘B’ Plant cooling water pump(PW)
  • ‘B’ Turbine Cooling water pump(TC)
  • ‘B’ Nuclear cooling water pump(NC)

-2 Charlie’s
• ‘C’ Condensate pump (CD)
• ‘C’ Normal chiller (WC)

-1 Alpha
• ‘A’ Heater Drain Tank Pump (ED)

-1 Small
• Small Normal chiller E02(WC)

Question 15

Who normally operated the breakers on the Non-class 4.16kv system?

Answer 15

•The Control Room normally does.

Could be operated locally IF needed

Question 16

How many ways can the breakers on the Non-class 4.16kv system(NB) be operated?

Answer 16

• 3 ways
  •Control room

•Electrically by locally turning hand switch on breaker front panel

•Mechanically on the breaker itself.

Question 17

How do you know one of the relays are activated on the Non-class 4.16kv(NB) breaker?

Answer 17

•The orange flag will be visible in the relay site glasses.
• The 86lock out will be activated (meaning 45deg angle and orange flag showing)

Question 18

How many ways can you tell that an 86 lockout is activated on the Non-class 4.16kv system?
activated meaning tripped

Answer 18

•The orange flag.
•86LO handle tilted 45deg.
•The white light is out.
•The green light glowing brighter.

Question 19

What does an 86 lockout do in the Non-class 4.16kv(NB) system?

Answer 19

•It trips the breaker
•It then prevents the breaker from being closed again until the trip condition is fixed and the 86LO switch is reset

Question 20

How does the 86 lockout relay reset and when can you do it?

Answer 20

•It can only be reset locally
• You can do it after you got permission from the CRS/SM

Question 21

What power does a Non-class 4.16kv breaker require to open or close, have indicating lights, or to use and of the UC, UT, UL, UE circuits?

Answer 21

•125VDC control power(NK)

Question 22

What do the indicating lights on the Non-class 4.16kv(NB) system mean?
Green, Clear, Red, White lights

Answer 22

•Red-breaker is closed and continuity through the trip coil

•Green- Breaker is open and if it’s brighter then the 86LO is activated

•White- The 86Lockout has power and isn’t activated

•Clear- The closing springs are charged (If light is off the breaker may not close)

Question 23

What do the closing springs do and how do they work?
(Non-class 4.16kv NB)

Answer 23

•They provide the mechanical force to close the breaker
•They are charged by a charging motor powered from 125vdc(NK)
•Discharged when they receive a ‘close signal’
•After the beaker closes the closing springs are immediately charged again!

Question 24

Describe the purpose of the NBN-S01 and NBN-S02 Fast Bus Transfer.

Answer 24

•The purpose of the NB fast bus transfer is to power the loads of a bus with loss of power due to a loss of Normal Service XFMR with a bus that still has a working Normal Service Transfer.

Question 25

What are the requirements for an Non-class 4.16kv(NB)fast bus transfer to occur?
Hint-theres 3

Answer 25

•The transfer switch is in Auto
•Neither NB buses can have an 86 lockout activated.
•Sync check must be acceptable
-Frequency
-Normal voltage

Question 26

Describe the purpose of the Engineered Safety Features(ESF) XFMR.
*NBN-X03 and NBN-X04

Answer 26

•It steps-down off-site power from 13.8kv to 4.16kv AND supplies PBA-S03 and PBB-S04

•It also can step-down 14kv from the SBOG’s and supply 4.16kv to PBA-S03(preferred) OR PBB-S04(alt)

Question 27

What are the Engineered Safety Features(ESF) XFMR’s isolations?

Answer 27

•The breakers upstream in NAN-S03 or NAN-S04

•Breakers downstream in PBA-S03 or PBB-S04

Question 28

Describe Cooling for OG and New style Normal Service Transformer’s and Engineered Safety Features XFMR’s

Answer 28

•2 phases

Phase 1- Natural air and oil circ. @ less than >70degC Winding temp

Phase 2- Natural oil circ and FORCED air @ 70degC Winding temp. (all fan banks running)
>70degC

Question 29

What does the ‘Nitrogen Blanketing’ do for the OG Normal Service XFMR and Engineered Safety Features XFMR?

Answer 29

•Has a nitrogen cylinder pressurized to 2,400psig
•Injects nitrogen regulated at .5psig just above atmospheric pressure
•Keeps air and moisture out
•Alarms in control room when CYLINDER is @200psig

Question 30

Describe the ‘Liquid Level Indicator’ on the OG Normal Service XFMR and Engineered Safety Features (ESF) XFMR.

Answer 30

•A float with a lever inside the XMFR, calibrated to 25degC so if the oil temp is at 25degC the level gauge will indicate 25degC
•As temp increases, oil expands/rises and the float rises and the indicator will indicate higher (vise versa for lower oil temps)

Question 31

Describe the mechanical relief on the OG and New style Engineered Safety Features(ESF) XFMR’s and Normal Service XFMR’s

Answer 31

•A spring loaded relief valve that reliefs excessive pressure.
•Raises a flag to alert locally
•Sends an alarm to the control room
•^ Both must be manually reset but the seat itself will close if the excessive pressure condition goes away

Question 32

Describe the Control Cabinet for the Normal Service XMFR’s and ESF XFMRS’s.

Answer 32

•Supplied from two different 480vac MCC’s normal and alternate

•Has an Automatic Bus Transfer(ABT) associated with it

-Front Panel
•Two lights that turn on to indicate power available from both supplies
•Controls for cooling fans & heaters
•An alarm panel

Question 33

Describe the Alarm Panel for Normal Service XFMR and ESF XFMR.

Answer 33

•12 alarms, powered from NK
•Tested daily but does not alarm the control room when tested.
•A real alarm does alarm the control room with a common alarm.
•Can clear the alarm locally but the control room alarm won’t clear until condition is cleared.

Question 34

Describe Electronic Temperature Monitor(ETM).

Answer 34

•Monitors Top oil and Winding temps.
•Housed in the control cabinet
•Has set point indicators
•Actuates the cooling fans using Winding temp.

Question 35

Describe the Constant Oil Pressure System(COPS)