Just to clarify, in a 240V 3 phase delta system, you must have ground fault monitoring, OR you must have a grounded phase, a.k.a. "corner grounded", in which case one of the phases will measure zero V to ground, the other two will measure 240V to ground and all 3 will measure 240V phase to phase. A 3 phase delta system without one or the other is a code violation.