Can a spot voltage set diagnose the cause?

No. It records one calculation from one measurement set. Cause review needs location, loading, instrument and project context.

Can I mix line-to-line and phase-to-neutral readings?

No. Use one comparable set only, either line-to-line or phase-to-neutral readings from the same record.

Voltage unbalance workflow

Measurement purpose

Voltage unbalance work should begin with a clean measurement set. The calculator uses three comparable voltage readings to show average voltage, maximum deviation and unbalance percentage.

The result is a measurement record, not a diagnosis.

Workflow

Record the measurement location.
Confirm whether the set is line-to-line or phase-to-neutral.
Record instrument, date, time and operating condition.
Enter the three comparable voltage readings and threshold basis.
Use the result to decide what project review is needed next.

Record table

Voltage unbalance record fields
Field	Record	Review concern
Measurement set	Vab/Vbc/Vca or Van/Vbn/Vcn	Do not mix modes
Location	Board, equipment or generator point	Cause can change by location
Instrument setup	Meter or analyser context	Setup affects confidence
Operating condition	Load, generator, inverter or time context	Readings need context
Threshold basis	Project, DNSP or equipment source	Not supplied by the page

Boundaries

Do not diagnose cause from unbalance percentage alone.
Do not mix readings from different times.
Do not treat a clean result as proof that no issue exists.
Do not hide the threshold source.