Measurement mode
Record whether V1, V2 and V3 are comparable line-to-line or phase-to-neutral values.
mode = line-to-line or phase-to-neutral
Input basis
Comparable V1, V2 and V3 measurements from one instrument time window.
Output unit
measurement basis
Use when
Use when V1, V2 and V3 are comparable measurements from the same mode and time window.
Boundary
Measurements need instrument, load state and time window context.
Not for
Site diagnosis, pass/fail threshold claim or equipment suitability decision.
Average voltage
Find the mean of the three comparable voltages.
Vavg = (V1 + V2 + V3) / 3
Input basis
Comparable V1, V2 and V3 measurements from one instrument time window.
Output unit
V
Use when
Use when V1, V2 and V3 are comparable measurements from the same mode and time window.
Boundary
Use one same-time instrument measurement set for review.
Not for
Site diagnosis, pass/fail threshold claim or equipment suitability decision.
Deviation
Find each voltage deviation from the average.
Vdev = abs(V1 - Vavg), abs(V2 - Vavg), abs(V3 - Vavg)
Input basis
Comparable V1, V2 and V3 measurements from one instrument time window.
Output unit
V
Use when
Use when V1, V2 and V3 are comparable measurements from the same mode and time window.
Boundary
Use the same measurement mode source for V1, V2 and V3.
Not for
Site diagnosis, pass/fail threshold claim or equipment suitability decision.
Maximum deviation
Identify the largest difference.
VdevMax = max(abs(V1 - Vavg), abs(V2 - Vavg), abs(V3 - Vavg))
Input basis
Comparable V1, V2 and V3 measurements from one instrument time window.
Output unit
V
Use when
Use when V1, V2 and V3 are comparable measurements from the same mode and time window.
Boundary
Does not diagnose project cause by itself.
Not for
Site diagnosis, pass/fail threshold claim or equipment suitability decision.
Percent unbalance
Display the unbalance percentage.
Unbalance% = VdevMax / Vavg x 100
Input basis
Comparable V1, V2 and V3 measurements from one instrument time window.
Output unit
%
Use when
Use when V1, V2 and V3 are comparable measurements from the same mode and time window.
Boundary
Threshold source and optional margin must be entered or governed separately.
Not for
Site diagnosis, pass/fail threshold claim or equipment suitability decision.

Average-deviation voltage-unbalance arithmetic.
Show voltage-unbalance measurement formulas without interpreting a site power-quality issue by itself.
Power-quality measurement context, National Electricity Rules context and project requirements govern interpretation.
Record V1, V2 and V3 as one same-time measurement set, including line-to-line or phase-to-neutral basis, instrument and time window; National Electricity Rules context may matter.

Voltage unbalance formulas
Relationship	Formula	Use	Boundary
Measurement mode	mode = line-to-line or phase-to-neutral	Record whether V1, V2 and V3 are comparable line-to-line or phase-to-neutral values.	Measurements need instrument, load state and time window context.
Average voltage	Vavg = (V1 + V2 + V3) / 3	Find the mean of the three comparable voltages.	Use one same-time instrument measurement set for review.
Deviation	Vdev = abs(V1 - Vavg), abs(V2 - Vavg), abs(V3 - Vavg)	Find each voltage deviation from the average.	Use the same measurement mode source for V1, V2 and V3.
Maximum deviation	VdevMax = max(abs(V1 - Vavg), abs(V2 - Vavg), abs(V3 - Vavg))	Identify the largest difference.	Does not diagnose project cause by itself.
Percent unbalance	Unbalance% = VdevMax / Vavg x 100	Display the unbalance percentage.	Threshold source and optional margin must be entered or governed separately.

This chart explains the measurement arithmetic.
The calculator owns entered threshold comparison.

Formula variables
Variable	Meaning	Unit	Use
V1	First measured line-to-line or phase-to-neutral voltage.	V
V2	Second measured line-to-line or phase-to-neutral voltage.	V
V3	Third measured line-to-line or phase-to-neutral voltage.	V
mode	Measurement mode.		Record line-to-line or phase-to-neutral consistently.
Vavg	Average voltage for the same measurement set.	V
Vdev	Maximum deviation from average.	V
VdevMax	Largest deviation in the measured voltage set.	V
threshold	Entered review threshold.	%	Record whether the threshold came from equipment, DNSP, project or standards context.
time window	Measurement time context.		Keep the load state and instrument record with the result.

V1: 404 V
V2: 397 V
V3: 401 V
Measurement mode: line-to-linesame instrument time window

Average the setVavg = (404 + 397 + 401) / 3 = 400.7 V.
Find maximum deviationThe largest deviation from average is about 3.7 V.
Calculate percentUnbalance% = 3.7 / 400.7 x 100 = 0.9%.

Voltage-unbalance estimateabout 0.9%

The value needs the measurement mode, load state, instrument record and threshold source beside it.

Use this as a measurement review record, not a site diagnosis or universal pass/fail threshold.

V1, V2 and V3 are comparable line-to-line values from the same time window.
Threshold source is recorded separately.

Limits of formula-only measurement review
Item	Value
Purpose	Show voltage-unbalance measurement formulas without interpreting a site power-quality issue by itself.
How to use the source	Average-deviation voltage-unbalance arithmetic.
Standards and project context	Power-quality measurement context, National Electricity Rules context and project requirements govern interpretation.
Where judgement is still needed	Use this chart to understand the relationship behind a calculation; do not treat it as a substitute for entered project values.
Before relying on it	Confirm current standards, local authority requirements, DNSP conditions, project documents and manufacturer data before relying on a decision.

Voltage unbalance formulas standards and project context
Context	Applies to	Public boundary
Measurement-set context	V1, V2, V3 line-to-line or phase-to-neutral voltage records	Use comparable measurements from the same instrument, load state and time window.
Threshold source	Entered review threshold and optional margin	Record whether the threshold comes from equipment, DNSP, project documents, National Electricity Rules context or another source.
Project review boundary	Voltage unbalance formulas chart	Confirm current Australian standards, local authority requirements, DNSP conditions, project documents and manufacturer data before relying on a decision.

Voltage unbalance formulas source basis
Item	Value
Source	AUWiring voltage-unbalance calculator formula notes.
Source type	Measurement record with standards context
Derivation basis	Derived from AUWiring calculator logic and user-entered measured voltages.
Last checked	2026-07-13
Review interval	Annual or when power-quality calculator formulas or measurement wording changes.
Review trigger	Formula change, measurement-record change, DNSP context change or project feedback.
Version used	R38-2026-07-13
Australian application	Australia; instrument setup, DNSP, equipment and project requirements govern formal interpretation.

Voltage unbalance formulas

Voltage-unbalance measurements from one record set

Measurement mode

Average voltage

Deviation

Maximum deviation

Percent unbalance

Average-deviation rows for voltage-unbalance records

Formula variables

Worked relationship example

Three-voltage unbalance reading

Where the voltage-unbalance chart belongs

Measurement basis for voltage unbalance

Use a calculator for project values

Voltage unbalance