AP-23 (loss vital DC bus)

Question 1

AP-23 (loss vital dc)

What is the “most” important feature/consequence of losing a vital DC bus?

Answer 1

• loss of vital DC bus (SD-11, 12, 13 or 14 ) will lose control power to associated AC bus
• when you lose the AC bus it will not transfer to SU
• now you have lost AC and DC …….and therefore also lost the PY

Question 2

AP-23 (loss vital DC)

If you lose a vital DC bus and Rx trips as a result, while you are traversing through E-0 you also have a loss of vital AC bus, DO you refer to ECA-0.3?

Why or why not?

Answer 2

No, if loss of a vital AC bus was due to the loss of the vital DC bus do not refer to ECA-0.3.

ECA-0.3 assumes you have DC power

Question 3

AP-23 (loss of vital DC bus)

Give major indications for loss of ….

SD 11

SD 12

SD 13

Answer 3

SD 11

• bus F control power (4kv, 480 kv bkr lights)
• Rx will trip on lo-lo L _s/g, TRN A, feed to SG 1 & 2 will be 0

SD 12

• bus G control power (4kv, 480 kv bkr lights)
• Rx will trip on lo-lo L _s/g, TRN B, feed to SG 3 & 4 will be 0

SD 13

• bus H control power (4kv, 480 kv bkr lights)
• Rx will NOT trip on its own (must be manually tripped by AP-23)