Corner-grounded delta service
A corner-grounded delta is a three-phase delta system with one phase conductor, usually the B-phase, tied to ground to hold all voltages to ground steady. The voltages from each phase to ground are not equal, so this arrangement does not suit single-phase loads. Because one phase conductor is grounded, it can be mistaken for an ungrounded phase. Clear phase identification is needed to avoid shock. Like other solidly grounded systems, a ground fault draws a large fault current, and that fault has to be cleared quickly. This arrangement is no longer common and is found in only a few existing facilities. Better options are available for new installations. On 480 V delta commercial services, co-located loads that cause repeated line-to-ground faults can turn the service into a corner-grounded delta in effect. In that case the PV system has to be isolated from the fault source to protect the inverters from excessive line-to-ground voltage. Some residential inverters list 208 V, 220 V and 240 V corner-grounded delta among their selectable grid configurations.
<!-- review notes
- sentence 1: support check: partial - Passages say one phase is grounded to stabilize voltages to ground and the B-phase is grounded in the figure, but "usually the B-phase" is not stated (only B-phase in that example).
- sentence 3: support check: partial - Passage says without proper phase identification there is shock risk since the grounded B-phase could be mis-identified, but it does not say it is mistaken for an ungrounded phase specifically.
- sentence 7: support check: partial - The passage lists 208, 220 and 240 V Delta Corner Grounded options, but nothing says they are residential inverters or selectable grid configurations.
- sentence 7: review: partial - The Fronius passage lists 208, 220 and 240 V Delta Corner Grounded options, but it does not say the inverters are residential or that these are selectable grid configurations. -->