WATERSPARKFALLS;Here are a couple Queries, per the Tanning Salon scenario:
1.: Was the 140VAC reading made with a High Input Impedance Voltmeter? (typical DVM).
In addition, was the L-G Voltage measurement similar to the L-N Voltage measurement?
Have you tried measuring the Voltage at the Receptacle(s), while the Circuit is "Loaded"?
Try measuring Voltage with an additional Load connected - such as a Large Incandescent Lamp, or a running Vacuum Cleaner.
See if this Test procedure stabilizes the L-N and L-G Voltage.
2.: As previously described by
TESLA, could the Receptacle(s) measuring 140VAC be fed from a 4 Wire Wye Voltage Boosting Autotransformer Setup?
Reference Schematics for assistance (from ECN Tech. Reference Section):
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Fig. 1a: Four Wire Wye Voltage Boosting Autotransformer Connection - Single Line Diagrammed View.
(3) 120/240V x 12/24V Isolated Transformers;
Primary Windings connected in Parallel (for 120V),
Secondary Windings connected in Series (for 24V).
Input: 208Y/120V 3ph. 4 Wire.
Output: 249Y/144V 3ph. 4 Wire.
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Fig. 1b: Four Wire Wye Voltage Boosting Autotransformer Connection - Standard Schematic View.
(3) 120/240V x 12/24V Isolated Transformers;
Primary Windings connected in Parallel (for 120V),
Secondary Windings connected in Series (for 24V).
Input: 208Y/120V 3ph. 4 Wire.
Output: 249Y/144V 3ph. 4 Wire.
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Another version of the 4 Wire Wye Voltage Boosting Autotransformer which might be used at the Salon would consist of (3) 120/240V x 16/32V Isolated transformers, with the Primary Windings connected in Parallel (120V), and the Secondary Windings also connected in Parallel (16V); which will result in an output of apx. 235Y/136V 3ph. 4 Wire.
Reference Single Line Drawing below:......................
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Fig. 2a: Four-Wire Wye Autotransformer; Voltage Boosting.
Parallel-Connected Primary Windings,
Parallel-Connected Secondary Windings.
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Measuring Voltage at an Outlet fed from one of these setups would result in an L-N reading of >136VAC, and be completely normal.
3.: There is mention of (2) Panelboards being driven by 208V-240V Transformers.
Are these Transformers "Reverse-Connected 240V 3ph. 3W Delta x 208Y/120V 3ph. 4 Wire"?
Verify there are no connections to the X0 on the 208 Wye side.
If the 240V Delta output is ungrounded, that could show odd L-G Voltages.
If these Transformers are 208V Input x 240V Delta Output, they could be either Center-Tap Grounded, Corner Grounded, or Ungrounded.
If there are L-N Loads being fed from these Transformers, they need to be Center Tap Grounded - with System Grounded Neutral Conductors Terminated to the Center Tap as well.
4.: Lastly, the >136V L-N reading might be a result of that particular Phase having no Load connected to it at the time of the Voltage Test, and the remaining Two Phases have moderate Loads connected.
Please reply with some additional information, per the Systems at this location.
--Scott (EE)