4160V

Question 1

State what 13.8 bus duct fault causes

Answer 1

Opens:

• Associated 345kV Breakers
• MGB for UAT bus duct fault
• 13.8 kV incoming Line breaker
• 4160 V incoming line breaker

Question 2

List causes of UAT incoming Supply Breaker trip

Answer 2

UAT/ Bus duct faults
345 bus 6/ 25kV Isophase bus fault
Switchgear enclosure fault
Breaker failure (11,12, MGB)
GSU fault

Question 3

List causes of RAT incoming Supply Breaker trip

Answer 3

RAT/ bus duct faults
345 kV Bus 5 fault
Switchgear enclosure fault
Breaker failure (345 kV 52, 695)

Question 4

List bus 3 and 4 UV auto actions

Answer 4

Trips large loads (94 relays)
-CO pumps first
-HD pumps next
Block RAT auto-transfer

Question 5

List bus 3 and 4 RAT Breaker Auto-Transfer

Answer 5

Sync exits or
existed within the last 1 second
Bus Voltage <17% and
UAT breaker begins to open - remote only
Available for 2.0 sec

Question 6

List Bus 5 and 6 Breaker Auto-transfer

Answer 6

Sync exits or
existed within the last 1 second
Bus Voltage <25% and
UAT breaker begins to open - remote only
Available for 1.2 sec

Question 7

List first and second level undervoltage

Answer 7

1st level:
- <70% voltage for > 1.2 seconds with RAT available
- <70% voltage w/o RAT
2nd level
- <95% rated voltage with an SI signal for >6 seconds

Question 8

List Bus 5 and 6 UV Auto actions

Answer 8

Trips large loads (94 relays)
Block RAT auto-transfer
UAT and RAT blocked open by RMO for Diesel to power bus