Complete Guide to Harmonic Distortion
The Harmonic Distortion Calculator computes THD (%) for voltage and current. Ensures IEEE 519 compliance.
What is THD?
THD = √(Σ H₂²…Hₙ²) / H₁ × 100%. Our Harmonic Distortion Calculator supports up to 50th order.
Why Control Harmonics?
Causes:
- Overheating: Transformers, cables.
- Tripped Breakers: False trips.
- Neutral Overload: 3rd harmonics.
- Equipment Damage: Motors, drives.
Use with Neutral Current and Transformer Size.
IEEE 519 Limits
| Parameter | Limit |
|---|---|
| V-THD | ≤ 5% |
| I-THD (ISC/IL < 20) | ≤ 5% |
| I-THD (20–50) | ≤ 8% |
| I-THD (>1000) | ≤ 15% |
Common Sources
| Load | Typical THD |
|---|---|
| PCs | 70–100% |
| LED Lights | 15–40% |
| VFDs | 30–50% |
| UPS | 5–15% |
Calculation Formula
THD = √(V₂² + V₃² + … + V₅₀²) / V₁ × 100
Example: Office Panel
V1 = 480V, V3 = 12V, V5 = 8V, V7 = 5V.
- Σ H² = 12² + 8² + 5² = 233
- √233 = 15.26
- THD = 15.26 / 480 × 100 = 3.18% → PASS
Mitigation
- Filters: Passive/active.
- K-Rated Transformers: Handle heat.
- Phase Shifting: Cancel 5th/7th.
- Line Reactors: Reduce I-THD.
Measurement
- True-RMS Meter: With FFT.
- Power Analyzer: Fluke 435.
- Up to 50th: IEEE requirement.
Practical Tips
- Separate Neutrals: Per phase.
- Oversize Neutral: 200% if >50% nonlinear.
- Monitor PCC: Point of common coupling.
- Derate Transformers: K-factor.
Common Mistakes
- Average Meter: Wrong THD.
- Ignore 3rd: Neutral burn.
- No ISC/IL: Wrong I-THD limit.
- Single Phase: Miss triplen.
Advanced
- TDD: Total Demand Distortion.
- K-Factor: Transformer rating.
- Crest Factor: Peak/RMS.
- Interharmonics: Non-integer.
Conclusion
Harmonics degrade power quality. Our Harmonic Distortion Calculator ensures IEEE 519 compliance. Pair with Neutral Current and Construction tools. Stay efficient with 1000 Calculators.