Not sure if this is an specific symbol or just trying to match a phasing arrangement.
The concept of transposition is relevant for HV overhead lines to balance the voltage between phases. For lower voltage usually line transposition is not required
The primary voltage on the auxiliary transformer unit no. 1 is 14.4kv with a secondary voltage of 2400V. I'm thinking this might be an iso phase bus where it is going to a conduit. Perhaps the notation for the phase changes is just to notify field personnel to test the lines and make sure the proper phases are connected on the other end. This symbol has been used for a low voltage as well, where it was going from a 480V control center to a 480V control center emergency section.
You usually want the phases ordered A-B-C from top to bottom or from left to right.
The "symbol" is not an actual symbol, it's just three lines crossing each other.
I attached an alternative to how to draw the circuit.
The diagram shows electrical topology, which may or may not have much to do with actual physical bus arrangements. The drawing shooterbooter provided is clearer.
We have shown similar phase crossings where we connected a utility with reverse phase rotation to a generator to indicate that the phases have to be rotated.
The drawing is meant to show the physical arrangement of the equipment and conductors when viewed from above. Shooter's alternative requires reconnecting the X bushings within the transformer and relabeling them on the outside. Probably easier to roll the conductors as shown.
It would be interesting to know what happens further to the right.
