Non Class 120VAC Instrument Power(NN)

Question 1

What kind of power does 120VAC instrumentation power supply ?

Answer 1

Single phase, 60hertz, regulated, and filtered power to four subsystems

Question 2

What’re the subsystems that get powered by NN system ?

Answer 2

NNN-D11;NNN-D12;NNN-D15;
NNN-D16

Question 3

What kind of equipment is in each subsystem ?

Answer 3

Normal/backup supply voltage regulators
A static switch between the voltage regulator supplies

Question 4

What is the normal power for the NN system ?

Answer 4

Non class MCC

Question 5

What is the emergency power supplies for NN system ?

Answer 5

D11&D12:Separate Class VAC MCC
D15&D16:Separate non class 480VAC SIAS load shed MCC

Question 6

What’re the 3 positions on manual bypass switch ?

Answer 6

Manuel transfer to normal/Automatic/ Manual Transfer Emergency

Question 7

How do the indicating lights work on static switch ?

Answer 7

Green:normal source
RED: emergency source

Question 8

What must happen to switch bypass switch to “AUTO” position ?

Answer 8

Break and make (will lose power to loads temporarily as you switch it back to auto )

Question 9

What is voltage regulating transformer for?

Answer 9

Step down voltage from 480VAC to 120VAC & to filter out transients from primary side to maintain steady output voltage on secondary side

Question 10

What is Voltage Regulating Transformer designed for ?

Answer 10

Designed to accept varying AC input voltage (+-15%rated),output voltage is well regulated filtered AC output; filters out transients from primary side to secondary side

Question 11

What does NNN-D11& NNN-D12 provide power for ?

Answer 11

Reactor control instru. & other station service loads
.FW control system
.Steam bypass control system
. CEDMCS
.Fuel pool instru.
.RCS&CVCS process instru.

Question 12

What did NNN-D15& NNN-D16 provide power to ?

Answer 12

Balance of Plant (BOP) & miscellaneous station service loads
.Plant annunciator cabinets
.Ground detection circuitry
.Control oil for turbine trip

Question 13

What kind of equipment does the Ground detection system have on D11&D12 ?

Answer 13

Ground detection relay, RED ground light, and reset push button

Question 14

What happens on loss of power to NNN-D11 ?

Answer 14

.CD: pump “B” mini flow fail open
.CH: letdown is lost
.RC:loss of PZR pressure control
.Reactor control(SF):reactor power cutback is disabled ; steam bypass valve failed closed

Question 15

What happens on loss of power to NNN-D12?

Answer 15

.CD makeup and draw off valves failed closed
.demons fail into full flow
.CD pumps A&C mini flow fail open
.level indication and makeup to (VCT)
.letdown lost
.loss of automatic control rod control

Question 16

What happens if you lose power to NNN-D15& D16?

Answer 16

Main feedwater pumps speed drops to about 300rpm, which will lead to reactor power cutback

Question 17

Where are the NN distributions panels located ?

Answer 17

D11&12:120ft control building
D15:100ft of turbine building
D16:120ft of Aux building