4160v

Question 1

STATE the function of the 4.16 kV distribution system

Answer 1

Supply power to various vital and non-vital 4.16 kV station auxiliaries

Question 2

DRAW and LABEL a simplified diagram of the 4.16 kV distribution system showing the power sources, transformers, and interconnecting breakers

Answer 2

Question 3

STATE the physical location of the 4.16 kV buses

Answer 3

• buses 3 & 4 non-safety related (located in non-essential switchgear room, 21’6” level)
• E5/E6 are safety related buses (located in essential switchgear room, 21’6” level)

Question 4

DESCRIBE the actions that have to be taken to manually transfer the 4.16 kV bus power supplies from the UATs to the RATs, and back to the UATs

Answer 4

Energize Synchronization system for RAT breaker to be closed, verify Synchronized Close RAT supply breaker Verify UAT breaker tripped, green flag breaker switch verify amber light out De-energize Synchronization system

Question 5

DESCRIBE the function of the remote safe shutdown (RSS) disabling switches located in the diesel generator room for the 4.16 kV bus 5 and bus 6 UAT and RAT incoming supply breakers

Answer 5

• RSS Disabling Panel switch a. isolation of closing circuit from control power b. used during fire conditions to prevent inadvertent shutting from fire induced circuit failures

Question 6

DESCRIBE the impact on 4.16 kV bus 5 and bus 6 RAT incoming supply breaker automatic shutting when the associated local-remote selector switch is in local

Answer 6

If in Local no Auto Transfer Available

Question 7

DESCRIBE the automatic actions that occur as a result of an extended undervoltage condition on 4.16 kV bus 3 or 4.

Answer 7

• No UV tripping of bus incoming supply breakers – without UAT going open no auto transfer – Trip (94 relays, large loads) • Condensate pump • Heater Drain pump • Blocks RAT auto transfer

Question 8

DESCRIBE the following line-ups of the 4.16 kV system: • 100% Power • 0% Power • Loss of AC (offsite)

Answer 8

• 100% Power - from generator through UATS to Buses • 0% Power - from offsite through UATS to buses • Loss of AC (offsite) - from the EDGs to bus 5 and 6 only

Question 9

Given a list of the 4.16 kV motor loads, IDENTIFY their correct bus power supply system

Answer 9

Bus 3 and 4 Loads • Typical Loads – Condensate Pumps – Heater Drain Pumps • Bus 4 – Start-up Feedpump (shutdown/startups -02DCR019) – Centac Service Air Compressor – LC-3 Bus 5 and 6 Loads • Safety related equipment • SW (pumps/fans), EFW (bus 6), CC – Emergency core cooling systems • RH, SI, CS pumps – Physically and electrically separated – Remote safe shutdown equipment

Question 10

Regarding SEN-282, HB Robinson Electrical Fault, DISCUSS the adverse effects of the inappropriate operator actions regarding the reset of the 86 device

Answer 10

operators used a normal operating procedure in an adverse condition and caused a larger casualty, that resulted in damage to the electric plant.