We ran into an issue recently regarding grounding of a delta, and had quite the heated argument regarding center-grounding of a delta connection. The switchboard was 3W delta, which is unusual for us. Motors and distribution transformers clearly don't care if the delta drifts, but the issue was that TVSS measures voltage from the lines to ground, as does the static switch of the delta-fed UPS on the switchboard, and both could malfunction if the delta became unbalanced and any of the phases drifted high or low with relation to ground. The generator was wired in WYE, so it was easy to ground the neutral tap to center the delta (no neutral connected, just the grounding jumper), but doing that causes some other issues...
