To effectively damp phase-to-ground overvoltage in an ungrounded system (with complete equipment grounding and bonding in place) the capacitance between phases and ground must be damped by a resistor connected from neutral-to-ground.
â€śCharging currentâ€ť for 480V systems is roughly 1 Ampere/1,000kVA of system capacity. [In the case of delta systems, the neutral has to be derived from zig-zag or wye-primaryâ€”delta-secondary transformers.]
Here is my favorite story
about the very serious problems that can occur with low-voltage ungrounded distribution.
[This message has been edited by Bjarney (edited 09-30-2004).]