In ,
Tom Horne wrote:

On May 29, 3:41*pm, (Don Klipstein) wrote:
In article , George wrote:

way from completely wrong with only a meter if you only had access to
the phase legs. Since a "Y" connection neutral is always bonded to
ground I could still get the same readings I described by placing one of
the meter probes on ground.

* It sounds easy enough for a 440V delta circuit to have all 3 legs
measure 277 volts from ground. *One way for that to happen is if there is
significant and equal stray capacitance from each leg to ground. *Another
is if someone connects a "Y" load to the circuit, and connects the load's
center point to ground.

*- Don Klipstein )

Don
If the load had a "center point," i.e. if it is star configured, It
would create a ground fault that would either trip the ground detector
if present or just sit there until a fault occurred on another phase
were upon the completely different voltage will probably damage that
load.

It surely appears to me that many old buildings lack ground fault
interruptors.

Thankfully, many, probably most buildings with 480V 3-phase are fed by
"Y" / "star" connected transformer secondaries. In which case, proper
neutrals are run (or at least are supposed to be). There is a common star
load in many of these buildings, often loading the 3 phases unequally:
277V lighting circuits.

--
- Don Klipstein )