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Power Quality Utility

Harmonic Distortion Calculator

Harmonic Distortion Calculator supports engineering calculations with transparent assumptions, practical result interpretation, and links to next-step technical resources.

Core Formulas

THD = sqrt(sum(Ih^2)) / I1 x 100%

TDD = sqrt(sum(Ih^2)) / IL x 100% (current only)

K-factor = sum(h^2 x (Ih / I1)^2) + 1

Enter RMS magnitudes for each harmonic order. The spectrum and summary metrics update in real time.

Harmonic Spectrum (% of Fundamental)

THD Result

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Dominant Harmonic

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Compliance Check

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Inputs & Outputs

Fundamental Voltage (V1)

Fundamental Frequency

THD Compliance Limit

Switch to Current THD mode to calculate TDD and K-factor metrics.

Total Harmonic RMS

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Total RMS

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Distortion Factor

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Harmonic Energy Share

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TDD

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K-factor

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Harmonic Input Table (Orders 2-15)

Order	% of Fundamental	Contribution
H2	—	—
H3	—	—
H4	—	—
H5	—	—
H6	—	—
H7	—	—
H8	—	—
H9	—	—
H10	—	—
H11	—	—
H12	—	—
H13	—	—
H14	—	—
H15	—	—

Harmonic Distortion Fundamentals

Harmonic distortion is a waveform-quality issue that directly affects transformer heating, neutral loading, protective-device behavior, and control-system reliability.

THD vs TDD

THD is normalized to fundamental amplitude. TDD is normalized to maximum demand current and is often preferred for current-distortion compliance discussions.

Dominant Order Identification

Pinpointing the strongest harmonic order helps you decide between source reactors, passive filters, active filtering, or distribution-level mitigation.

Equation Reference

Reference equations used by this calculator for distortion metrics and quick thermal screening.

Topic	Equation	Meaning
Total harmonic distortion (THD)	THD (%) = sqrt(sum(Ih^2)) / I1 x 100	Compares total RMS harmonic content to the fundamental component.
Total demand distortion (TDD)	TDD (%) = sqrt(sum(Ih^2)) / IL x 100	Current-only metric referenced to maximum demand current instead of fundamental current.
Distortion factor	DF = I1 / Irms = 1 / sqrt(1 + THD^2)	Indicates how much of total RMS remains in the fundamental component.
Transformer K-factor (screening)	K = 1 + sum(h^2 x (Ih / I1)^2)	Weights higher-order harmonic currents more heavily for thermal stress indication.

Measurement Workflow Matrix

Use this matrix to connect harmonic distortion outputs to mitigation and upgrade decisions.

Scenario	Objective	Recommendation	Critical Checks
Drive-heavy panel commissioning	Identify dominant harmonic orders from multiple VFD-fed motor branches	Enter measured harmonic RMS current by order and compare THD/TDD against plant quality targets before tuning line reactors or passive filters.	PCC location, demand-current reference, meter bandwidth class
Voltage quality screening	Confirm bus voltage waveform quality for sensitive automation devices	Use Voltage THD mode and monitor dominant orders to determine whether distortion is source-side or load-side coupled.	Instrument transformer ratio, grounding quality, sampling interval
Transformer thermal review	Evaluate harmonic-related transformer stress trend	Use Current THD mode and K-factor result as a fast pre-check to decide if detailed thermal loading analysis is required.	Transformer nameplate K-rating, ambient temperature, duty cycle