Don,
Are you referring to Fig. 1-1: Multigrounded Common Neutral Drawing?
If so, I'm not sure if the system would be best described as 3 wire or 4 wire.
The Common Star point for the Wye connected Secondary Coils (AKA "X0") is driven to ground and a Grounded Conductor is brought out from the Star point.
The Grounded Conductor is bonded to the Center Tapped Grounded Conductor used on the 120/240 VAC 1 phase 3 wire Secondaries.
Also, one end of the Primary Coil on the 1 phase Transformers is connected to the same Common Grounded Conductor.
Looking at the Medium Voltage Feeders leaving the Delta / Wye Transformer, the system looks like a 4 wire Wye.
Looking at the rest of the system, it seems to be 3 wire - except where the side of the Primary coils are terminating to the Common G.C., then it leans back towards 4 wire again.
I'm unsure if it would be best classified as 4 wire since the Grounded Common Conductor is also Common to the low Voltage Secondaries.
Anyone have an answer???
Thanks for bringing this up for discussion.
Scott S.E.T.
