Hello, u2slow;
I have dealt with many Dual Metered Services, such as the ones you are describing.
One Gear Section (w/ KWH Meter) for
120/240 VAC 1Ø 3W "LIGHTING",
and another Gear Section + KWH Meter for
240 VAC 3Ø 3W "POWER".
Most likely, the PoCo's Transformer bank is a 4 Wire Delta - could be an Open Delta, or a Closed Delta configuration used - I have seen them both used, depending on the location.
I have seen a few locations with 3Ø 3W "Power" as a 3 Wire Closed Delta arrangement, and the 1Ø 3W "Lighting" from a single phase Transformer, for Customers with dual Services.
These were in areas which were primarily Commercial / Light Industrial, whereas the 4 Wire Deltas were in Commercial / Residential type areas, but seen plenty of 4 Wire Deltas in Commercial / Light Industrial areas too.
The 4 Wire Deltas were Pole Mounted Configurations, consisting of:
<OL TYPE=A>
[*] On Open Deltas: very large 1Ø Transformer, with all secondary taps used, and a smaller 1Ø Transformer used to create the 3Ø "C" leg,
[*] On Closed Deltas: Center Xformer used for 1Ø 3W is maybe 200% + the size of one of the two Outer Xformers.
</OL>
The 130-140 VAC reading may be either from the type of Meter used, or simply what is being delivered from the PoCo at that time - like at a low usage time, or maybe the P.F. is Leading (Capacitive Reactance).
The 140 VAC is reaching the "Excessive" limits, but should not be too concerning unless there is Equipment which does not like that high of Voltage - and this is also measured at the Equipment during operation.
Let us know what you find after the next visit.
Scott35
