Harmonic THD
Harmonic THD meaning in Australian power-quality measurement records.
Meaning in harmonic measurement records
Harmonic THD means total harmonic distortion. It is a power-quality measurement value calculated from a fundamental magnitude and harmonic magnitudes, usually in a 50 Hz Australian low-voltage context.
The term should stay attached to the measurement point, voltage or current type, analyser/report context and operating condition. Without those fields, a THD value is too easy to misread.
Fundamental, harmonic orders and RMS basis
Harmonic THD records need to show what was measured and how the entered values relate to the fundamental. Keep the formula relationship visible, but do not treat the page as a universal harmonic-limit source.
| Record context | Keep visible | Why it matters |
|---|---|---|
| Measurement point | board, equipment or supply location | Shows where the distortion value belongs |
| Quantity type | voltage THD or current THD | Prevents different measurement types being mixed |
| Harmonic data | fundamental RMS, harmonic RMS rows and analyser condition | Keeps the calculation traceable |
Voltage THD and current THD are separate
Voltage THD and current THD are related power-quality terms but they are not the same record. A report should identify which quantity is being measured before a threshold or guide is considered.
THD also does not diagnose the source of distortion by itself. Utility, equipment, loading condition, instrument data and project thresholds remain separate sources for interpretation.
Using THD measurements
Use the harmonic THD calculator for entered values and the formula chart to understand the relationship. Use the power-quality measurement table when the record needs the measurement point, analyser context and threshold basis kept visible.
Source and review
Check the terminology source, review timing and Australian application before carrying this term into a project record.
| Item | Value |
|---|---|
| Source | AUWiring harmonic THD calculator wording, THD formula chart and power-quality measurement record table. |
| Source type | Australian terminology |
| Derivation basis | AUWiring Australian glossary term; no utility limits are reproduced as universal pass criteria. |
| Last checked | 2026-07-13 |
| Review interval | Annual terminology review or sooner if harmonic THD calculator wording changes. |
| Review trigger | Update when THD calculator, formula chart or measurement table fields change. |
| Version used | T42-2026-07-13 |
| Australian application | Australia; Australian English power-quality terminology. |