ECN Forum Forums Code Related Discussion NEC & other Code issues Overhead Three Phase 13.8 & 4160 Delta

You ground / bond to the case of the transformer.

The OCPD trips only after the SECOND line faults to ground. That's why phase monitors are required.

Non-NEC compliant solution: Slap the foolishness out of this customer- there's no reason to preserve an ungrounded delta.