SBO Electrical

Question 1

What powers the SBO during normal conditions?

Answer 1

Bus 11 from high side of Bus 16

Question 2

What feeds the U2 125vdc Alt Battery?

Answer 2

MCC 65-1 under normal conditions. IF LINED UP TO U2, MCC 29-2 will feed MCC 65-1 (safety related bus feeding MCC 65-1)
All loads will shed from MCC65-1 prior to setting this lineup

Question 3

What happens to the SBO on a loss of 138kV Bus 3 or TR 12?

What actions must be taken upon this condition?

Answer 3

SBO will lose power.

Power must be restored to SBO within one hour of loss of power or else SBO must be declared NON-FUNCTIONAL due to loss of battery charger

Question 4

What is the purpose of the crosstie between Bus 61 and 71?

Answer 4

for maintenance purposes or loss of Bus 11 ONLY.

Not to cross tie busses under ACCIDENT condition

Question 5

What causes a trip of the a trip of the breakers from Bus 11 to 61/71?
How are they reset?

Answer 5

Trip on Bus 11 undervoltage.

Must be manually reset

Question 6

How are the Bus 61/71 4kv breakers field indication of proper operation?

Answer 6

2 white lights indicate continuity through trip and close fuese

Question 7

What power sources are available to the SBO?

Answer 7

AC during normal operation - Bus 61
DC - each SBO has dedicated 125vdc system to provide electrical power to for startup and operation, 4kv breaker operation, SBO lube oil circ pump operation during event, and various functions

Question 8

What is the deisng basis of the SBO 125vdc batter?

Answer 8

they can do their design function for 1 hour following a loss of battery charger. Therefore, after one hour without a charger, the batteries must be considered not available for SBO system and system declared INOP

Question 9

What consists of the SBO DC systems?

Answer 9

125vdc batter 6A (7A)
Normal battery charger powered from 65-1/75-1
125vdc switchboard 6A(7A and distribution panel 6A-1(7A-1)

Question 10

What is the purpose of the maintenance charger and it’s power supply?

Answer 10

Located on U3 side and powered from 75-1. available to supply power source to U2 or 3 SBO battery though a maintenance switch

Question 11

What interlock exists for the SBO DC Maintenance charger?

Answer 11

Interlock so that it can supply the SBO battery for U2 or U3, but not both simultaneously.

Question 12

How is the SBO UPS configured?

Answer 12

Normal power from 125 vdc dist panel via inverter
If inverter fail or loss of 125vdc dist panel, the static switch (normal seek w/ 30 sec. TD) will transfer over to MCC 65-1 via isolimiter

Question 13

What provides normal power to SBO UPS?

Answer 13

125vdc dist panel via inverter 6B (7B) and manual bypass switch

Question 14

What happens on an SBO UPS INverter failure?

Answer 14

On an internal fault, the static switch would automatically swap to align the UPS dist panel to MCC via specially metered transformer called an isolimeter

Question 15

What is the SBO UPS Static Switch?

Answer 15

Auto transfers to supply manual bypass switch from either 125vdc or isolimeter.
Auto transfers back to inverter 30 sec after inverter conditions return to normal, provided auto retransfer logic toggle switch is in ON position.

Question 16

How can the SBO UPS be transferred to the Isolimeter?

Answer 16

Automatically or Manually via Manual Bypass Switch

Question 17

What is the purpose of the SBO Isolimiter?

Answer 17

Rectified AC powered from MCC 65-1 (75-1) and is alternate feed to SBO UPS

Question 18

What condition is the SBO in when MCC/Isolimeter is powering the SBO UPS?

Answer 18

Must be declared INOP

Question 19

How does the Airstart tran swap and overcrank logic work for the SBO?

Answer 19

The selector Switch chooses which bank to start on
Starts and attempts to roll the engine. If it doesn’t reach 80 rpm in 4 seconds, it will attempt using the other train.
If engine fails to reach 200rpm in 10 seconds of start signal, OVERCRANK lockout will prevent future starts until reset.

Question 20

What happens at 450rpm during SBO Startup?

Answer 20

At 450 rpm, DG will pause momentarily while bearing oil pressure is below 20# until it reaches 20# in BOTH engines, then rolls DIRECTLY to 900rpm

Question 21

Which Engine trips are NOT bypassed?

Answer 21

Overspeed,
Generator Ground
Generator Differential

Question 22

What stops SBO from going over 450rpm with oil <20#?

Answer 22

PLC

Question 23

What happens on a PLC or DCS Failure?

Answer 23

Complications with startup but not prevented. PLC taken to bypass w/local switch

Question 24

Which PLC bypassed what is the only allowed way to start the SBO?

Answer 24

Local Emergency Start

Question 25

How is an emergency shutdown performed for SBO?

Answer 25

press e-stop button and hold down until full stop
Take overspeed trip level upward until it trips
Take Fuel Rack level to minimum position and hold until complete stop
Close fuel cut-off valve

Question 26

During a Normal SBO Startup, what are the milestones ?

Answer 26

0 rpm - start signal received - airstart system initiates
80-200 rpm - engine begins firing and air start solenoids de-energize at 200
200 - radiator fans start, air start solenoids de-energize, immersion heater de-energize, ventilation starts, sumps lockout
200rpm +30 sec - lo-lo lube oil pressure trip enabled
450rpm - DG runs here unloaded for 5 minutes
750 rpm - AC fuel oil backup pump autostart
750rpm +45 sec - lo jacket water pressure trip enabled
900rpm - FULL SPEED

Question 27

During a normal SBO Startup - What happens at 450rpm?

Answer 27

DG Runs with no acceleration and unloaded for 5 minutes

Question 28

With PLC in bypass, how is SBO started?

Answer 28

Local Emergency Start ONLY

Question 29

What happens to SBO w/ CS initiation?

Answer 29

If SBO is in “NORMAL”, the SBO output breaker at Bus 23 or 24 is tripped to prevent confusing the ECCS load shed function

If in “SBO” Mode, Breaker trip logic for UV and ECCS is bypassed.