Actually, the Grounded Conductor [Center Tapped "Neutral" in 1 phase 3 wire, or Common in 3 phase 4 wire Wyes] always has Voltage on it. On a 120/240 VAC 1 Phase 3 wire system, the Grounded Neutral Conductor is 120 VAC [there is 120 VAC between it and one of the two Ungrounded Conductors].
If the Center Tap or Common was not Grounded at the Transformer + Service, this will not make the system Dangerous - just Ungrounded.
Take the 3 wire Delta for example:
If the system is "Corner Grounded", one "Phase" is Grounded at the Transformer + Service and the system has a Grounded Conductor. This system will draw high currents on either Ground Faults or L-L / L-L-L Faults. The Voltage to Ground is stabilized on this system.
If the system is Ungrounded, there is no Grounded Conductor or bond between the system and the Metallic Raceways, or the Earth it's self.
A Ground fault will draw very low current levels. L-L / L-L-L faults will draw large current levels.
The Voltage to ground is not stable, as it would be on a solidly Grounded system.
This means that the Voltage from a given Conductor and at different points in the system can vary when applied across Impedances above 1K ohm.
This will kill a person, but not even come close to tripping an OCPD.
Just wanted to mention this.
Scott SET
