Hello,
I understand that systems being fed by delta - delta transformers can either be corner grounded, center tap grounded, or ungrounded. Corner ground systems I understand that the phase to phase voltage is say 480V in a 480V system. For Phase to ground on 2 of the phases would be 480V. On the third one it would be 0V. For the corner grounded delta system I can see how 240.85 requires full voltage rated breakers and not allow slash rated since the 480V will be over the 277V rating. However, for ungrounded systems, why would the same be required? Is there actually a voltage reference from phase to ground? (I understand there will be some capacitive coupling)
I understand that systems being fed by delta - delta transformers can either be corner grounded, center tap grounded, or ungrounded. Corner ground systems I understand that the phase to phase voltage is say 480V in a 480V system. For Phase to ground on 2 of the phases would be 480V. On the third one it would be 0V. For the corner grounded delta system I can see how 240.85 requires full voltage rated breakers and not allow slash rated since the 480V will be over the 277V rating. However, for ungrounded systems, why would the same be required? Is there actually a voltage reference from phase to ground? (I understand there will be some capacitive coupling)
