Non-Class Elec Dist. (NA, NB, NG, NH) COPY Flashcards
What is the electrical flow path from the Startup Yard to the WRF NB system for the Cooling Tower Make Up and Blowdown (TB) system?
Do these NB busses have cross tie capability?
NAN-S05/S06 -> NBN-X05/X06 -> NBN-S05/S06
Yes
On a 13.8 kV (NA) breaker, what does the red light mean?
Breaker closed
continuity through trip coil
On a 13.8 kV (NA) breaker, what does the Green light mean?
Breaker Open
On a 13.8 kV (NA) breaker, what does the bright green light mean?
Breaker tripped on fault
breaker racked to test
On a 13.8 kV (NA) breaker, what does the white light mean?
status of lockout relay
if light is ON, relay is reset and continuity through it
On a 13.8 kV (NA) breaker, what does the clear light mean?
closing springs are charged
What are the control room indications for a breaker?
Red light - breaker closed & continuity through trip coil
green light - breaker open
bright green light - breaker tripped on fault or racked to test
voltmeter on B01
ammeter on B01
What is the Startup Oscillograh for?
Multi-channel transient recorder (Digital Fault Recorder) that detects and automatically records power system abnormalities in analog and on-off event form.
When do the closing springs recharge for big breakers?
immediately after discharging to close the breaker
When do 480 VAC LC breaker closing springs recharge?
when the breaker reopens
What is the purpose of Anti-pumping protection?
to ensure that the breaker only attempts to close ONCE per control switch operation
prevents closure attempt with an uncharged spring
When would you have to locally manually operate big breakers?
loss of control power
Can we parallel power supplies locally electrically on non-class busses?
No
there are interlocks that prevent multiple supply breakers from closing at the same time when operating the breaker locally electrically
What is the purpose of the synch switch in the control room in relation to operating breakers?
enables closure of multiple supply breakers in parallel
energizes synch indications on B01
What is the purpose of the Line Breakers Control Transfer Switches regarding the 525kV SRP Switch Yard breakers?
Provides permissives to operate the SRP breakers from the Unit 1 control room
What are the two positions for the 525kV line breaker Control Transfer Switches?
PDO - SRP Control only
CON RM1 / PDO - allows Control Room control
What indications are available for voltage on the EAST and West Busses in the SRP Switchyard?
two digital meters on U1 B01
What alarm window indicates degraded or loss of voltage on the East/West busses in the SRP Switchyard?
EAST/WEST 525 KV SWYD LO/LO-LO VOLTS
(1B06B)
What is a “ring bus” regarding the SRP Switchyard?
the East/West Busses that are connected to each other in 8 locations
Regarding SRP Switchyard design, why is the ‘breaker and half scheme’ important?
transmission lines, startup transformers and main transformers connect between 525kV breakers. This ensures two paths that current can take in the switchyard.
prevents huge impact from a single fault (breaker failing open)
What voltage does the AE-ZYN-X05 transformer step down to from 525 kV?
12.47 kV
What is each Start-up transformer secondary winding designed to have the capability of doing?
Start and carry half the auxiliary loads of one unit while feeding one train of ESF loads of one of the two other units
How are the control and indication signals sent to/received from NAN-S05/S06?
Controls are hardwired and indications are multiplexed
What are the requirements for fastbus transfer on NAN-S01/S02 busses?
Bus XFR switch in AUTO.
Generator trip or MT trip (Zero VARs signal)
Early ‘b’ contact on S01 normal supply breaker must be closed
Synch check relay satisfied
NO bus lockouts
Voltage available on NAN-S03/04
When do the cooling fans start on the normal service transformer?
When “hot spot” temperature reaches 70C, if in AUTO
Where can we reset lockouts on non-class breakers (NA, NB, NG, NH)?
Locally ONLY
Where do MCC’s get control power from?
The magnetic starters get control power from downstream of circuit breaker
what features are lost when a Non-Class breaker loses control power?
remote breaker operation
electrical protection trips
How do you manually charge closing springs on high voltage breakers?
5/8” ratchet attached to the end of a charging motor
What two 86 lockout relays are featured on 480 VAC LC breakers?
Bell alarm
Ground fault (50G)
what is the bell alarm on the 480 VAC LC breakers?
White reset button provides local indication of:
overcurrent trip
breaker rack out interlock
Why are start up transformers physically and electrically separated from each other?
minimize the possibility of a single failure affecting more than one transformer
What are the isolation boundaries for the startup transformers?
two 525kV breakers
13.8 kV breakers on switchgear
motor operated disconnects (MOD)
What are the startup transformer stages of cooling?
<70C - Natural circ of oil, no fans
70C - first stage of cooling fans, forced circ of oil
>70C - second stage of cooling fans added to first stage, forced circ of oil
How does the Open Phase Detection system work for Startup Transformers?
trip function disabled
CR alarm when open phase is detected
Where are all the NAN-S05/S06 supply breakers controlled from?
Where are the load breakers controlled from?
Unit 1 can control ALL of the supply breakers, U2 and U3 can only control their respective supply breakers
load breakers are controlled from their respective units
What protective relays are available for the Startup transformers?
Differential Current
Neutral Ground Fault
Overcurrent
Sudden Pressure
Open Phase Detection
When will the supply breakers to WRF open automatically?
SIAS or CSAS
and
switchyard reaches low voltage setpoint
Which bus supplies power to the SRP Switchyard for smaller loads?
NAN-S05
Where does NAN-S05/S06 receive control power from?
How is it aligned?
NKN-M45/M46 through NKN-U45/U46
transfer switches
Where do NAN-S03/S04 get control power from?
NKN-D41/D42
Where do NAN-S01/S02 get control power from?
NKN-D41/D42
What happens in the plant if the Main Generator fails to trip on reverse power?
Zero VARs signal is generated to promptly initiate a fast bus transfer
this prevents the Rx from tripping on low DNBR on the loss of RCPs
Requirements for NAN-S01/S02 manual transfer
Synch switch ON
if NAN-S01/S02 energized, synch check satisfied
NO bus lockouts
voltage available on NAN-S03 and NAN-S04
NAN-S01/S02 normal supply breaker trips?
Generator trip
bus overcurrent
during manual bus transfer, when alt supply breaker handswitch returns to normal after closing
What is a coast down trip?
Generator trip concurrent with LOOP (loss of voltage on NAN-S03/S04)
NAN-S01/S02 remain aligned to UAT
all breakers except RCPs open on NA busses
RCPs maintain flow through the core as they coastdown for 20 seconds or until <80% voltage (whichever comes first)
What electrical protection does the NAN-S01/S02 busses have?
overcurrent
undervoltage & negative phase alarm in CR
undervoltage relay for motor breakers and LC breakers
undervoltage relay for coastdown trip
Big picture, how do we remove an NAN-S01/S02 bus from service
not an outage for other bus
verify app. for loads lost
remove loads from bus
Unit in MODE 5, 6, or defueled
secure CW pumps
secure RCPs
transfer NB bus to other NB bus
make sure both supply breakers are open
What kind of cooling do the Normal Service Transformers have?
Forced Air/Oil
(air is blown across the cooling fins filled with oil)
On the Normal service transformers, what is the purpose of the Auto-Throwover switch?
auto transfers control cabinet power supply to the alternate on a loss of the normal supply
must be manually reset
What powers the Normal Service Transformer control cabinets?
NH
What protection does the normal service transformer have?
sudden pressure fault relay
differential current
phase and ground over current
what does the synch switch do for NBN-S01/S02 busses?
closes the tie breaker
opens to associated normal supply breaker when the control switch is returned to normal
what are the requirements for NB auto bus transfer?
B01 Bus Transfer Switch in AUTO
Normal Service Transformer NBN-X01 FAULT
NBN-S01 Normal Supply breaker OPEN (early “b” contact)
Voltage sensed on NBN-S02
Synch Check relay satisfied
No lockout on either bus
manual NB bus transfer requirements
what happens if you take the handswitch to the wrong position?
synch switch aligned
NBN-X01/X02 NOT locked out
no lockout on either NB bus
the wrong breaker will trip (dont overshoot, either)
Where do NBN-S01/S02 get control power from?
NKN-D41/D42
individual control power breakers (RRC) inside the breaker cubicle
Purpose of the kirk key interlock?
prevent opening the mechanical disconnect under load
What indications are available for LCs in the control room?
breaker position
voltage
Where are LC main feeder breakers normally operated from?
B01
can be locally also
Where are MCC breakers operated from?
locally ONLY
where do MCC breakers get control power from?
itself, downstream of the breaker
What could bring in this alarm window?
generator lockout
fault on the UAT
What could bring in this alarm window?
startup transformer lockout
What could bring in this alarm window?
525kV breaker(s) tripped
What could bring in this alarm window?
undervoltage/negative sequence on the bus. UNIT 1 ONLY
What could bring in this alarm window?
525kV startup transformer supply breaker tripped
What could bring in this alarm window?
loss of control power to the SU Transformer protection circuits
Unit 1 ONLY alarm
What could bring in this alarm window?
undervoltage
negative sequence
loss of control power
cooling fan failure
What could bring in this alarm window?
issue with digital fault recorder
UNIT 1 ONLY
What could bring in this alarm window?
when 13.8 kV breakers are paralleled
What could bring in this alarm window?
supply breaker lockout
undervoltage
negative sequence
loss of control power
undervoltage load shed
cooling fan trouble
What could bring in this alarm window?
4.16 kV breakers in parallel
What could bring in this alarm window?
trip or problem with transformer
must be investigated by AO if not a trip
What could bring in this alarm window?
transformer high temp
bus undervoltage
main feeder breaker lockout
each LC has its own window
What could bring in this alarm window?
potential Tech Spec issue concerning off-site power capability
What could bring in this alarm window?
low switchyard bus voltage
excessive load on the metering circuitry (sync switch on)
loss of power to WRF trip permissive relays (NKN-D4303)
loss of power to voltage metering (NNN-D1116)
What could bring in this alarm window?
issue with transformer
AO must investigate
UNIT 1 ONLY
Describe the response of the Non-Class Distribution system to a failure of power
NA -
NB -
complicates operation of the plant
loss of RCPs - Rx trip
loss of CDPs and EDPs - FWP trip on low suction psi and have to feed S/Gs with AF
