Utility vs. Customer Phase Rotation - Level III Test Question (Recent 7/16)

[BRAD2121]

Thoughts on this?

A utility defines their horizontal bus at the customer point as ABC left to right facing the customer with ABC rotation. The customer defines their buses as ABC left to right facing the utility but with CBA rotation. For a first time connection the customer has to:

A: Swap A & B phases and leave phase sequence alone
B: Swap B & C phases and leave phase sequence alone
C: Leave phasing alone and change phase sequence to ABC
D: leave phasing and phase sequence alone.

I guessed D because and don't know if I'm right. Is there a proper procedure here? Explain if possible.

[marvinray]

I would also choose D. Utility is Rotating A-B-C left to right, so if customer is wired C-B-A then the rotation would naturally be C-B-A left to right. What gets confusing is which side of the line you are looking at. They try to trick you by saying "facing the utility" or "facing the customer". It's easier if you draw it out and flip it around.

A-B-C (Utility)
--------
C-B-A (Customer)

[mike37311]

I took the exam last Friday 1-27-17 and answered this question with D also.

[stevenl569]

Thoughts on this?

A utility defines their horizontal bus at the customer point as ABC left to right facing the customer with ABC rotation. The customer defines their buses as ABC left to right facing the utility but with CBA rotation. For a first time connection the customer has to:

A: Swap A & B phases and leave phase sequence alone
B: Swap B & C phases and leave phase sequence alone
C: Leave phasing alone and change phase sequence to ABC
D: leave phasing and phase sequence alone.

I guessed D because and don't know if I'm right. Is there a proper procedure here? Explain if possible.

D is the correct answer. If you read through A,B, and C choices they are all having the same effect on the sequence/phasing. Basically they are all the same answer with different means of getting there.

[jrm5116]

Heres another way to look at it visually as well that helps see the rotation swap.