Class Elec Dist. (PB, PG, PH) Flashcards
What are the SIAS load shed MCCs and their load groups?
M19 and M71 are Load Group A
M20 and M72 are Load Group B
Where does the PB system get control power from?
PK
What is the result of PB breakers losing control power?
local operation ONLY
As a PB breaker closes, what happens to the opening and closing springs?
opening springs charge
closing springs remain charged regardless of breaker position
What is the purpose of the arcing contacts on breakers?
close first and open last to ensure arcing damage occurs to them instead of the main contacts
What are the two purposes of the anti-pumping feature on breakers?
ensures the breaker attempts to close only once per control switch operation
prevent a breaker closure attempt with an uncharged closing spring
If control power is lost, how are the closing springs charged?
manually with a 5/8” ratchet
How are the ESF transformers cooled?
fans blow across oil filled fins
natural circ for oil
hot spot temp to auto start fans is 70*C
When the ESF transformers get a fault, what else happens?
lockout relay trips the high side breaker (NAN-S03/S04) and both the low side breakers (PBA-S03/PBB-S04)
What loads shed from the PBA-S03 bus on a SIAS?
Normal chiller ‘A’
Aux. feed ‘N’
What are the limits and logic for degraded and undervoltage relays to trip on a LOP?
Degraded
<90% for:
7 seconds with a SIAS
35 seconds without SIAS
Undervoltage:
<75% for 2 seconds
2 of 4 logic
Where can PB breaker lockout relays be reset?
control room and locally
How are PB breaker lockout relays reset?
taking control switch to TRIP
What are the PB normal supply breaker closing permissives?
no lockouts on ANY of the supply breakers
sync switch on (if closing from the CR)
DG and ALT supply breakers open (if closing locally)
Gen. Diff. Lockout relay reset
When do the PB normal supply breakers auto trip?
BOP-ESFAS load shed
ALT supply breaker closed with sync switch on
ESF transformer fault
overcurrent lockout (86)
What could bring in this alarm?
The alarm will be generated by a number of bus problems:
undervoltage (3675 V),
negative sequence,
control power failure,
closing spring not charged,
a sustained (10 second) degraded voltage (3745 V)
condition
What could bring in this alarm?
Generated by a lockout actuation on the supply breaker.
In response to this, the DG will start BUT will not have a
spray pond pump operating. In this case, the DG is required
to be emergency stopped locally.
What could bring in this alarm?
4.16 kV breakers in parallel.
Expected alarm when transferring power supplies to a bus.
What could bring in this alarm?
This alarm indicates either a trip (which will be accompanied
by a number of additional alarms) or a problem with the
transformer.
An AO must be dispatched to investigate the local
annunciator panel.
What could bring in this alarm?
Alarm is received when an undervoltage or degraded
voltage relay actuates.
BOP ESFAS will act accordingly to strip the bus and start
the DG.
What could bring in this alarm?
Load Centers L31, L32, L33, L34, L35, L36 each have their
own alarm.
Alarm is generated by:
a high temperature condition in the transformer,
bus undervoltage or
control power failure
in L31/L32, failure of the Electronic Temperature
Monitor, its 240V power supply, or forced cooling
system
What could bring in this alarm?
Alarm is generated by a lockout of the Main Feeder breaker
What could bring in this alarm?
Common alarm for all class MCCs that are fed from PGAL33
The MCC (PHA-M33, PHA-M37, and NHN-M71) can be
determined by looking for a green light on one of the MCCs
on B01.
What could bring in this alarm?
This alarm is only associated with PGA-L33.
Alarm is generated by:
a high temperature condition in the transformer,
bus undervoltage or
control power failure
