ECN Forum Forums General Topics of the Trade General Discussion Area 480 Open Delta voltage readings

The POCO said there was a problem with the voltage readings on a 480 open delta service. the readings were around 480V phase to phase. the readings from phase to ground were 486,410 and 87. The POCO said the phases should be within 5% when reading to ground. They said the low reading on one of the legs indicated a ground fault. They said this low voltage reading was an early warning and that if another leg went to ground it would be a direct short. I found an electrical engineers forum in which one of the members posted that the line to ground voltages were of no significance. I was wondering if anyone has any experience with this and could maybe submit an explanatory diagram showing a short situation as mentioned so it is easy to understand.