Just for educational purposes, this is out of my "Electric Machinery Fundamentals" textbook:
1. If the primary voltage is positive at the dotted end of the winding with respect to the undotted end, then the secondary voltage will be positive at the dotted end also. Voltage polariites are the same with respect to the dots on each side of the core.
2. If the primary current of the transformer flows into the dotted end of the primary winding, the secondary current will flow out of the dotted end of the secondary winding.
From another section of the same textbook:
...the dots help determine the polarity of the voltages and currents in the core without having physically to examine its windings. The physical significance of the dot convention is that a current flowing into the dotted end of a winding produces a positive magnetomotive force, while a current flowing into the undotted end of a winding produces a negative magnetomotive force. Therefore, two currents flowing into the dotted ends of their respective windings produce magnetomotive forces that add. If one current flows into a dotted end of a winding and one flows out of a dotted end, then the magnetomotive forces will subtract from each other.
Now, a lot of that doesn't apply here since there is only one black dot on each transformer. Looks to me like they just want to make sure you get all three CTs wired with the same polarity so they are additive. Terminals I11, I21, and I31 should be connected to the line side of each phase, respectively.
iwire said:
How is power factor determined in that case? Average?
As you know, the power factor is a ratio of real power to apparent power. If you were combining two circuits into one set of readings, the power factor will be the the real/apparent ratio for the combination of the two feeders. It would be a completely different value than the power factor for either of the two feeders themselves.
As long as it took me to type all of that, someone else has probably already responded with a much more informative and helpful post in the meantime...(edit: I was wrong!)