Solid "B" Phase Delta Corner Grounding

These are older systems that you usually don't see any more. They are used as a three wire three phase system that powered older manufacturing sites. What you initially describe is exactly correct in the design considerations. If you want more information you may want to take a look at the Electrical Engineers Handbook.

There not a lot of new publications put out on this because of its age, most newer facilities are designed differently and these older sites will eventually be phased out.

always something new: i think it goes back when transformer were less reliable, if one transformer were to go bad you would still have 3 phase voltage, with less power, till a replacement was found. also you could think of this as a single phase wiring method, a 2 pole fusible disconnect, 3 conductors, 1 grounded, 2 @ line voltage above ground. perry