Harmonic Distortion Chart

Use this worksheet after the calculator result to record harmonic percentages, THD, true RMS values, true power factor, dominant harmonic order, PCC notes, resonance flags, and follow-up review items.

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Quick reference table

A harmonic distortion chart is a calculator-led planning record, not a harmonic study substitute. It keeps fundamental voltage, fundamental current, individual harmonic orders, THD, true RMS values, dominant harmonic, PCC context, resonance flags, and power factor impact together before IEEE, utility, manufacturer, or equipment review.

Harmonic distortion worksheet

Harmonic distortion worksheet
Checkpoint	Record from calculator	Review note
System basis	System type, voltage, current, 60 Hz basis	Confirm measurement point, load state, and PCC context
Harmonic content	3rd, 5th, 7th, 11th, 13th values	Identify dominant harmonic order and load source
Distortion result	Voltage THD and current THD	Compare with applicable project or utility limits
RMS impact	True RMS voltage and current	Review heating, neutral current, and equipment loading
Power factor impact	True power factor and distortion factor	Coordinate with capacitor correction review

Harmonic follow-up routing

Harmonic follow-up routing
Finding	Record before action	Likely next review
High 3rd harmonic	Neutral current, phase balance, single-phase nonlinear loads	Neutral loading and panel measurement
High 5th or 7th harmonic	VFD, rectifier, UPS, or charger load group	Manufacturer filter or reactor review
Capacitor bank present	Capacitor kVAR, switching state, resonance flag	Resonance and filter application review
Voltage THD concern	PCC location, utility point, affected equipment	Utility and facility power-quality review

Formula basis

THD percent = sqrt(sum of individual harmonic percent values squared). True RMS = fundamental RMS x sqrt(1 + (THD / 100)^2).

Fundamental RMS is the 60 Hz voltage or current basis used by the calculator.
Individual harmonic percent is the harmonic order value relative to the fundamental.
THD is the root-sum-square distortion value.
True power factor combines displacement power factor and distortion factor in the calculator workflow.

Worked examples

VFD harmonic screenRecord load type, fundamental current, 5th and 7th harmonic content, current THD, true RMS current, and whether filter or manufacturer review is needed.

Capacitor resonance flagWhen a capacitor bank is already installed, keep capacitor kVAR, dominant harmonic, switching state, and resonance notes beside the THD result before adding correction equipment.

Assumptions. Balanced load and line-to-line voltage assumptions behind this chart.

The worksheet assumes harmonic percentages are measured values or intentionally selected planning values.
Filter design, resonance review, capacitor application, and utility point-of-common-coupling review require deeper analysis than this worksheet.
THD at one panel does not describe the whole facility unless the measurement point, load state, and monitoring interval are documented.

Code and standard notes. Planning limits that should be checked before final equipment selection.

Use this chart as a calculator-led planning record; verify IEEE harmonic practices, utility requirements, equipment manufacturer limits, measured data, adopted NEC requirements where applicable, and AHJ or facility requirements before mitigation.

How to use this chart

1Start with the harmonic setCopy each harmonic order value and the fundamental voltage and current basis from the calculator result.

2Identify the controlling resultRecord whether voltage THD, current THD, true RMS current, dominant harmonic order, or true power factor is driving the follow-up.

3Route mitigation reviewUse the worksheet to list measurement, utility, filter, capacitor, VFD, UPS, or equipment manufacturer review items.

Worksheet checklist. Record source basis, review gaps, and assumptions before using the chart result.

Capture measurement basisDocument system type, measurement point, PCC context, fundamental values, load type, and power factor basis.
Capture distortion valuesRecord individual harmonic percentages, voltage THD, current THD, dominant harmonic, true RMS voltage, and true RMS current.
Capture action notesList whether the result points to monitoring, filtering, equipment derating, capacitor review, utility coordination, or manufacturer support.

Common mistakes to avoid. Review these before turning chart current into an equipment decision.

Using typical harmonic values as if they were measured data without labeling the assumption.
Adding capacitors for power factor correction before checking whether harmonics or resonance may affect the equipment.
Reporting THD without the measurement point, load state, dominant harmonic order, and whether the value is voltage THD or current THD.

Frequently asked questions

These answers explain how to use the chart without turning a quick reference into a final design decision.

Is THD enough to choose a harmonic filter?

No. THD helps screen the condition, but filter work also needs system impedance, resonance review, load profile, equipment data, and manufacturer guidance.

Why does harmonic distortion affect power factor?

Distortion can lower true power factor even when displacement power factor looks acceptable, so power factor correction should be reviewed with harmonics in mind.