I'm having trouble understanding how a pole mounted transformer is wired. I am astounded at how little information is online about one of the most common devices on the grid. The typical single phase transformer has a single wire connection from one high voltage power line. To have a complete circuit on the primary side of the transformer, there must be another wire to which it's connected. Am I correct in assuming that the other connection is to the multi grounded neutral? If so, does the multi-grounded neutral carry current for all 3 phases of the high voltage lines? Does this MGN wire originate from the substation transformer? It appears that the the secondary, neutral tap from the transformer is also connected to the MGN, which also seems confusing.