Complex Power Question, when to use current conjugate

I was hoping someone could help me out with explaining when you use these two particular forumulas.

Solving for 3 phase power:
1) S = sqrt 3 * V line to line * I line to line
2) S = 3 * V line to neutral * I' line to neutral
where I' is the conjugate of I


I've seen equations #1 and #2 but I have not seen the equation
3) S = sqrt 3 * V line to line * I' line to line

Does equation #3 exist or is it incorrect?

Thank in advance.

I can't quite understand the concept of

I line to line

Current is what flows in a wire, or line. If a meter is being used to measure current, only one line is connected to.

Voltage is measured from line to line, so

V line to line

or

V line to neutral

makes sense.