.AR Elect. Class dist. (Welch's Highlighted Notes)

Question 1

PBA-S03 / PBB-S04:

• Control Power…
• B Train Special Considerations…

Answer 1

PBA-S03 / PBB-S04 (4160V Class Switchgear)

• Control Power: PKA-D21 / PKB-D22
• B Train Only: Breakers have remote / local switches (App. R) to separate MCR wiring / controls.

Question 2

Switchgear Protective Relaying:

• Degraded and Undervoltage UV Relays…
• Inputs to BOP-ESFAS?…
• UV Relays Indication in MCR?

Answer 2

• Bus Undervoltage Relays (4 PTs supply a voltage signal to 8 UV relays.)
  
  • 4 Degraded Voltage (~90% for ~35 seconds)
    
    • Time delay shorter if SIAS actuates (~ 7 seconds)
  • 4 Undervoltage (~78% for ~ 2 seconds)
  • Input to BOP ESFAS (2 of 4 logic):
    
    • DG start
    • Load shed
    • DG breaker close interlock
    • Starts load sequencer
  • Each relay has a white light in the MCR. Dark during under voltage.

Question 3

Switchgear Protective Relaying:

• State the various protective relays (other than UV’s…)
• State the Lockout Relays MCR indications, alarms…
• How do you remotely reset a Lockout Relay from the MCR?

Answer 3

• Bus Undervoltage and Negative Sequence Relays (alarm)
• Motor Phase Overcurrent Relays (Trips BKR. Light overload causes alarm)
• Motor Ground Fault Overcurrent Relays
• Bus Feeder Phase Overcurrent and Neutral Residual Overcurrent Relays
• Lockout relays:
  
  • MCR alarm, Bright Green indication
  • SEIS alarm
  • Reset remotely from the MCR by placing the HS to TRIP (class equipment only)

Question 4

Normal / Alternate Supply Breaker Interlocks:

• State the Interlocks…
• What’s special ONLY about the Alternate Breaker?…
• What happens on an “Automatic trip”?…

Answer 4

Normal / Alternate Supply Breaker Interlocks:

Closing Interlocks:

• No lockout on the three supply breakers
• Sync switch turned ON (MCR closure interlock)
• Other two supply breakers (DG and ALT) must be open (Local closure interlock)

*Alternate BKR ONLY:* DG breaker must be open (prevents cross tie of DGs)

Automatic trip:

• BOP-ESFAS load shed (LOP)
• Alternate Supply Breaker is closed with synch switch in ON. (Normal board transfer)
• ESF XFMR fault
• Bus overcurrent generated by lockout

Question 5

ESF Service XFMRs (NBN-X03, X04):

• What happens at 70°C?…

Answer 5

ESF Service XFMRs (NBN-X03, X04)

• 70°C (winding hot spot) - Fans turn on in Auto
• Normal and alternate power to control cabinets (NH)
  
  • Auto transfers to alternate
  • Manual transfer back to normal
• Transformer Protection
  
  • Sudden Pressure Relay (SPR)
  • XFMR Differential
  • Phase and Ground Overcurrent

Question 6

13.8 kV / 4.16 kV Breaker Indications:

State what these indicating lights mean…

• Red light
• Green light
• Bright Green
• White light
• Clear Light
• Both Red and Green lights being dark means…(bonus question…)

Answer 6

13.8 kV / 4.16 kV Breaker Indications

• Red light: Lit if breaker closed and Trip coil has power
• Green light: Lit if breaker open.
• Bright Green light: Breaker tripped on fault or racked to TEST. (Resistor to light is bypassed)
• White light (SWGR only): Lit if l_ockout relay is reset_ and functional.
• Clear light (SWGR only): Lit if closing spring is charged (limit switch for spring)
• Breaker stuck closed with a trip signal: Both red and green lights dark. (looks like a loss of control power)

Question 7

Breaker Seismic Positions:

• What if PB breaker is fully racked down (disengaged)? Actions?
• Do temporary conditions (planned and attended like opening SWGR doors, breaker racking evolutions) render the BUS Inoperable?
• Limit on how many PB breakers can be rackout/disconnected per LC to meet seismic requirements?

Answer 7

Breaker Seismic Positions

• PB breaker in fully racked down (disengaged) position requires the adjacent breakers to be declared inoperable (not seismically qualified in this position).
• Temporary conditions that are both planned and attended such as opening switchgear doors or performing breaker racking evolutions will NOT render bus inoperable.
• PG breakers: limited to 8 breakers being rackout / disconnected per load center to meet seismic requirements.

Question 8

PHA/PHB (480V MCCs):

• How many MCCs per Train? (#’s)…
• MCC’s Locations?…
• What is its control power?
• What happens to MOV override if control power is lost? (or Relay drops out)…

Answer 8

PHA/PHB (480V MCCs)

• 4 MCCs per train. (M31 to M38)
• M31 / M32 located in Control Bldg. Others in the Aux Bldg.
• Control power to motor controllers fed down stream of breaker (XFMR and fuses in the breaker bucket)

MOV Override is lost (resets) if control power is lost (MCC powered). (OR relay drops out)

Question 9

SIAS Load Shed MCCs:

• How many SIAS Load Shed MCCs?…
• What happens on a SIAS?…
• How are they restored?…

Answer 9

SIAS Load Shed MCCs

• 4 Non-Class MCCs (two per load group)
  
  • Feed essential Non-Class IE loads.
• Trip off from SIAS
  
  • NHN-M19 and NHN-M71 (Load Group A)
  • NHN-M72 and NHN-M20 (Load Group B)
• Restored by resetting at associated PG supply breaker

Question 10

4.16 kV Circuit Breaker Operations (GE Magne-Blast ACBs):

• How are they closed?…
• How are contacts held together?…
• How is the tripper bar used?…
• Explain the Anti-Pumping protection…

Answer 10

4.16 kV Circuit Breaker Operations (GE Magne-Blast ACBs)

• Closed by two closing springs. Spring charging motor, controlled by limit switches, charges the closing springs.
• As breaker closes, opening springs are compressed and contacts are held together by a mechanical latch.
• When closed, the opening springs are charged and ready to force the contacts open when mechanical latch is released.
• Tripper bar used to unlatch the opening springs (electrically via trip coil or manually with a linkage)
• Anti-pumping protection:
  
  • Ensures breaker only attempts to close ONCE per control switch operation. Anti-pumping relay seals in through the control switch and blocks further closing attempts. Drops out when switch is released.
  • Prevents breaker closure attempt with an uncharged spring. Anti-pumping relay energized whenever the closing spring is not in the fully charged state.
  • Stays energized as long as switch is held in the close position OR until the spring recharges, whichever is longer.

Question 11

LCO 3.8.9 Distribution Systems – Operating (Modes 1-4)

• Required trains to be operable?…
  
  • LCO time if 1 train INOP?…
• What happens if 2 or more distribution systems are INOP? LCO time?…

Answer 11

LCO 3.8.9 Distribution Systems – Operating (Modes 1-4)

• Requires both trains of PBs / PGs / PHs to be operable.
  
  • One train inoperable: 8 hours or RICT
• Two or more inoperable distribution subsystems cause a loss of safety function: 1 hour or RICT (cannot voluntarily enter)

Question 12

LCO 3.8.1 AC Sources Operating (Modes 1-4):

• How many off-site circuits & DGs to be operable?…
• How many load sequencers to be operable?
• is LCO 3.0.4.b applicable to the DGs?
• Explain LCO 3.8.1 Condition A…

Answer 12

LCO 3.8.1 AC Sources Operating (Modes 1-4):

• Two off-site circuits and two DGs operable
• Train A and B Automatic load sequencers operable
• LCO 3.0.4.b is NOT applicable to the DGs
• One off-site circuit inoperable (Condition A)
  
  • 1 hour (then every 8 hours): verify the off-site circuit is operable
  • 24 hours: declare required supported feature(s) inoperable when redundant feature(s) is inoperable
  • 72 hours or RICT: restore operability

Question 13

LCO 3.8.1 AC Sources Operating (Modes 1-4):

• Explain LCO 3.8.1 Conditions B…

Answer 13

• One DG inoperable (Condition B)
  
  • 1 hour (then every 8 hours): verify operable off-site circuit(s)
  • 4 hours: declare required supported feature(s) inoperable when redundant feature(s) is inoperable
  • 24 hours: common cause evaluation OR run the other DG
    
    • If operability restored within 24 hours, common cause will be addressed by CAP.
  • 10 days or RICT: restore the DG
    
    • Extended DG outages (> 72 hours) require comp actions to be taken (SBOGs, SU XFMRs, SWYD, Main & UATs, AFA, EDG, weather, switching)
    • If any comp action is not met, enter in CAP, manage the risk and restore without delay.

Question 14

LCO 3.8.1 AC Sources Operating (Modes 1-4):

• Explain LCO 3.8.1 Conditions C, D, E, F, G, H…

Answer 14

LCO 3.8.1 AC Sources Operating (Modes 1-4):

• Two off-site circuits inoperable, restore one in 24 hours or RICT (Condition C)
• One off-site and one DG inoperable (Condition D)
  
  • 12 hours or RICT: restore one
  • Enter LCO 3.8.9 if power is lost. (3.0.6 exception)
• Two DGs inoperable, restore one in 2 hours or RICT (cannot voluntarily enter Condition E)
• One load sequencer inoperable (Condition F)
  
  • Restore in 24 hours or RICT
  • 4 hours: declare required supported feature(s) inoperable when redundant feature(s) is inoperable
• One or more offsite circuit(s) do not meet required capability (Condition G)
  
  • 1 hour: Restore capability (Restore voltage, Block FBT (preferred) or transfer PBA/PBB to DGs)
  • G is only applicable if the PB bus has old DV relays (U1 PBA only until 2020 fall outage)
• ≥ 3 power sources inoperable: restore within 1 hour OR RICT (cannot voluntarily enter Condition H)

Question 15

LCO 3.8.1 AC Sources Operating (Modes 1-4)

• Bases…
• Min/Max SWYD voltage?…
• Explain “Last Unit online”
  
  • MVAR output ≤ 0…
  • MVARs > 0…
• What do minimum voltage and required capability prevent?…
• Is there an LCO limit on high SWYD voltage?
• Hz limit for operability?…
• DG Fuel Oil Day tank minimum level?

Answer 15

LCO 3.8.1 AC Sources Operating (Modes 1-4)

Bases:

• An offsite circuit may be connected to both PBA & PBB and not violate separation criteria.
  
  • Associated S/U XFMR must not be connected to NAN-S01 or S02 and Fast Bus Transfer is blocked
  • Ensures adequate voltage to ESF equipment.
• Offsite circuit inoperable:
  
  • Not connected to a PB bus.
  • Unavailable to commence auto load sequencing for a DBA
  • If available for sequencing, but a DBA could cause PB DV relays to actuate, enter Condition G for U1 PBA only (not A/C)
  • Reduced capability and/or low SWYD voltage could impact Conditions A and C.
• Required Capability:
  
  • Offsite circuit’s ability to maintain rated frequency and voltage while accepting loads during an accident.
  • Under conditions where these voltage changes would result in inadequate voltage to ESF equipment or tripping of degraded voltage relays, the affected offsite circuit(s) do NOT meet their required capability.
• Minimum SWYD voltage is 518 kV (higher voltage required based on electrical line-up, up to 528.5 kV)
• If two or more units are on line, SWYD voltage will not change significantly following trip of one unit.
• Last unit on-line:
  
  • Must have MVAR output ≤ 0 (not supporting grid voltage) or block FBT to ensure adequate post-trip grid voltage.
  • If outgoing MVARs (> 0), post-trip SWYD voltage could lower. Adequate voltage to the Class 1E buses is assured by blocking fast bus transfer. Minimizes loading and voltage drop on SU XFMRs.
• Minimum voltage and required capability prevent a double sequencing event during a DBA. (DV relay actuation)
• No LCO limit on high SWYD voltage (Max voltage ≤ 535.5 kV. If exceeded, offsite circuits remain operable)
• No Hz limit for operability (controlled by APS EEC, unit trip would have minimal effect)
• Fuel Oil Day Tank (550 gallons (2.75’ or 55%) – minimum Tech Spec level (SR 3.8.1.4)
  
  • Exceeds the 60 minute fuel supply requirement with 10% margin (438 gallons)

Question 16

What Happens on the following Alarm?…

• 4.16KV IE TR A(B) SPLY BKR LKO TRIP

Answer 16

• Alarms:
• 4.16KV IE TR A(B) SPLY BKR LKO TRIP
  • Lockout actuation on the supply breaker.
  • DG will start BUT not tie on. (No SP pump – emergency stop DG)