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What are the conditions that would initiate a 2R to 1R transfer (Station Power Transfer)?
- 2R Lockout
- 2RS Lockout
- 3N4 Bkr Open
- 345KV Bus 1 Lockout
- 8N4, 8N7, 8N10 breaker failure
When will bus 11 and 12 transfer to 1R during a station power transfer?
- Bus 11 will automatically transfer to 1R when bus 11 residual voltage is <25%
- Bus 12 will normally not automatically transfer but will remain available for manual operation if required. Bus 12 will transfer to 1R IF: Bus 11 is locked out or 152-104 is not closed AND Bus 12 residual voltage is below 25% of the normal rated voltage.
- NOTE: No automatic transfer exists from 1R transformer to 2R transformer
- NOTE: Station power transfer will NOT occur if 1R is de-energized.
During a Station Power Transfer, the 11 Recirc MG Set Drive motor breaker fails to trip. After the transfer, #12 RFP is running and bus 11 is not energized. Is this expected?
Yes, due to the fact that the recirc mg set field breaker did not open, that bus will not transfer. Since the bus won't transfer, bus 12 will pick up upon the recirc mg set field breaker.
The plant was in a refueling outage when a plant transient occurred resulting in a station power transfer. Following the transient, buses 11 and 12 are BOTH energized. Is this expected?
Yes, due to the fact that neither of the busses had a RFP running, the logic will restore both buses provided that both recirc mg set bkrs opened.
The plant is operating at 50% power with #12 RFP providing feed flow. A station power transfer occurs due to a fault on 2R. What is the status of buses 11 and 12 following the transfer?
both buses will remain energized with #12 RFP still running due to logic setup.
What is the status of Bus 13 and Bus 14 after a station power transfer and the loads supplied from them?
Buses 13 and 14 will be re-energized from 1R when residual bus voltage is less than 25%, however, the CWP's will not restart.
The plant is operating at Normal Operating Conditions when DW pressure reaches 1.84# due to a transient. What, if any, equipment is Load Shed at this point? How would this differ if plant electrical loads were supplied from the EDG's or 1AR?
- DW cooling fans
- RHRSW pumps
- If supplied from 1AR or EDGs, the following will also be shed:
- 11 (12) CRD
- 11/13 (12/14) RHRSW
- 15 Compressor (Div 1 only)
- 1/3 (2/4) DW cooling fans
- 11 (12) FPCC pump
- 11 (12) RBCCW pump
Describe the Loss of Voltage EBT.
- When bus voltage (as sensed by a 1 out of 2 twice logic) lowers to <2625 VAC,
- T=0 - Initiate EDG Fast Start Signal
- - Initiate 5 & 10 second timer
- - Inhibit degraded voltage transfer
- T=5 - Trip NORMAL supply breakers
- - Initiate 1AR transfer
- - 1AR supply bkrs will close if
- All supply bkrs are open
- Bus voltage <25%
- 1AR supply bkrs are in AUTO
- T=10 - Trip normal supply breakers
- - Trip 1AR supply breakers
- - Initiate EDG Auto Transfer IF:
- NO bus lockout exists
- Alternate supply bkrs are open
- Bus Voltage <25%
- EDG supply bkrs are in AUTO
- EDG >870 RPM, voltage >3776 VAC and not overspeeding and generator field is fully developed w/in 3 sec of a field flash (125 RPM).
During an EBT, what is the status of Bus 13 and Bus 14?
These buses are NOT re-energized from any source (with exception of LC-107).
What is the source of control power for 4KV breakers within the plan?
D-111 and D-211 from D-11 and D-21 respectively.
Why does an EBT NOT occur when a station power transfer occurs?
The EBT loss of voltage logic WILL start, however, power will be restored PRIOR to the 5 second timer timing out which resets the loss of voltage logic prior to initiating a transfer to 1AR and initiate the EDG's.
Describe a Degraded voltage EBT.
- On each essential bus, there are 3 degraded voltage sensing relays with contacts arranged in a 2-out-of-3 logic pattern. If degraded voltage (3920) on a bus is sensed for 9 seconds, the logic scheme will:
- 1) Trip the bus tie breaker
- 2) Initiate a transfer to the 1AR transformer
- 3) Start both EDGs
- If acceptable voltage exists on 1AR transformer, the bus will remain on 1AR and the transfer to the EDG's will NOT be completed. If degraded voltage exists on the bus powered from 1AR transformer for another 5 seconds:
- 4) 1AR source breaker will be tripped
- 5) Transfer of the affected bus to its respective EDG will be initiated.
Concerning an EBT to 1AR, what are the requirements for this transfer to occur?
- EBT switches are in SETUP
- 1AR 4KV bkrs in AUTO
- Voltage is present on 1AR
- ALL supply bkrs to bus 15 and 16 are OPEN
- 1AR transfer logic is made-up for either: loss of voltage for 5 seconds, OR degraded voltage for 9 seconds, OR loss of voltage on 1R.
- An automatic transfer to the EDGs has NOT been initiated by loss of voltage on the essential bus for 10 seconds.
When the 1AR transfer relays are energized (during an EBT), they will shed:
- RHR pumps
- CS pumps
- CRD pumps
- RHRSW pumps
- MCC-131 and 132 (141 and 142B)
- Turbine AOP (Bus 15)
- Bus tie bkrs
The plant is at normal operating conditions when a disturbance occurs. Following the transient, conditions are as follows:
Station power is from 1AR
DW pressure is 1.0 PSIG
Rx Water level is -125" and has been <-47" for 23 minutes
Rx Pressure is 310 PSIG
What is the status of the RHR pumps?
A) All RHR pumps are running, but will not be able to perform their required function due to no room cooling
B) All RHR pumps are running and injecting into the vessel as designed
C) All RHR pumps were load shed due to the ECCS load shed logic
D) All RHR pumps are running but NOT injecting into the vessel.
D) All RHR pumps are running and injecting into the vessel as designed by the ADS system. These pumps are NOT load shed for ECCS load shed logic.
(this multiple choice question has been scrambled)
What equipment is load shed when station power is supplied from 1AR or the EDGs and an ECCS signal is received?
- Parentheticals are DIV II:
- 11 (12) CRD pump
- 11, 13 (12, 14) RHRSW pump
- VRF-1, 3 (2, 4)
- 11 (12) FPCC pump
- 11 (12) RBCCW pump
- 15 Compressor
- (12 SW pump)
Which loads are shed during an ASDS transfer load shed?
- 12/14 RHR pump
- 12 Core Spray
- 12 CRD
- 12/14 RHRSW
- Tie Bkr
- (Same loads as ECCS load shed for Div 2 except SW pump 12)
What is the power supply for the 2R transformer auxiliary and control power?
MCC-131 and MCC-121. Normally aligned to MCC-131 and is equipped with an ATS, which will transfer to it's alternate source if voltage degrades to <90% rated volts for 1 second.
What are the two potential power sources for the 1AR transformer?
- 10 bank transformer
- 1ARS (345KV - 13.8KV)