Delta might be impedance grounded or perhaps not grounded at all?
so could wye, and they say "SOLIDLY GROUNDED wye", not just solidly grounded
i did run across a study that suggested grounded wye secondary configuration faults have higher fault current, but i think that would make the grounded wye having less of a need for GFPE because the GFPE in my mind is for lower current fault or pulsing, the higher available current should be more likely to open the OCPD under ground fault conditions
