Three-phase voltage unbalance
Compare three simultaneous line-to-line RMS readings. This magnitude calculation does not determine relay settings or negative-sequence voltage.
Enable JavaScript for live calculations. Read the method and default example below.
Method and assumptions
- Unbalance (%) = 100 × maximum absolute deviation from the average / average.
- Use line-to-line readings taken under the same operating condition.
Before using the result
- No pass/fail limit or trip delay is selected. Check equipment limits and investigate supply conditions with a qualified engineer.
- This method uses voltage magnitudes only; it is not an IEC negative-sequence calculation.
Worked example
Illustrative default inputs. Enter your project values above.
- L1–L2 voltage
- 415 V
- L2–L3 voltage
- 410 V
- L3–L1 voltage
- 420 V
Default results
- Average line voltage
- 415 V
- Maximum deviation
- 5 V
- Voltage unbalance
- 1.2 %
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Technical references
These references support planning. The exact model documentation and a project-specific engineering review govern the final specification.