Delta ground is derived from the primary side of the xfmr at each substation in the plant. I know how it works and my boss found out the hard way when he got zapped by the L2 on a control circuit.
Actually a funny story, him and two other guys were troubleshooting a starter, one had a the L2 in his hand (?), leaned on another guy and then he leaned on the foreman who was in contact with the side of the box. Don't know how they did it, but needless to say they all got a buzz.
