Power Quality Symptom Chart

Use this worksheet after the calculator result to record symptom lane, voltage sag or swell, frequency deviation, THD, flicker, interruption class, event timing, affected equipment, and measurement follow-up.

Open calculator

Quick reference table

A power quality symptom chart is a calculator-led planning screen, not a diagnosis by itself. It connects the result type with measured voltage, frequency, THD, flicker, interruption, event time, and affected equipment so the next step can be monitoring, utility review, equipment manufacturer review, or harmonic analysis.

Power quality symptom worksheet

Power quality symptom worksheet
Symptom lane	Record from calculator	Follow-up note
Voltage sag or swell	Deviation percent and classification	Confirm measurement point, duration, and affected load
Frequency variation	Hz deviation and quality label	Check generator, UPS, utility, or source condition
Harmonics	THD and dominant harmonic order	Use harmonic worksheet for detailed distortion review
Flicker	Pst, fluctuation, or severity result	Correlate with switching, starting, or welding loads
Interruption	Duration, time, and severity label	Document event time and equipment response

Symptom-to-field-review routing

Symptom-to-field-review routing
Observed issue	Record before escalation	Likely next review
Lights flicker when a motor starts	Event time, starter type, voltage dip, affected panel	Motor starting and voltage-sag monitoring
VFDs or UPS alarms recur	Alarm time, THD, voltage, load state, firmware or manual limit	Equipment manufacturer and harmonic review
Controls reset randomly	Sag or interruption duration, branch circuit, control power source	Time-stamped monitoring at the affected equipment
Utility service complaints	Meter point, event log, demand interval, affected loads	Utility contact and facility measurement record

Formula basis

Voltage deviation percent = (measured voltage - nominal voltage) / nominal voltage x 100.

Nominal voltage is the reference voltage entered in the calculator.
Measured voltage is the field or instrument value being screened.
THD is total harmonic distortion entered or calculated for the selected analysis path.
Event classification is the calculator label that guides follow-up measurement and equipment review.

Worked examples

Voltage sag follow-up recordRecord nominal voltage, measured voltage, deviation percent, event time, motor or load starting state, affected equipment, and whether utility or equipment review is needed.

Flicker complaint worksheetFor a lighting flicker complaint, keep switching time, measured fluctuation, panel location, nearby large load, and repeat-measurement plan beside the calculator result.

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

The worksheet assumes calculator inputs come from measured values or clearly labeled planning assumptions.
A single calculator result does not replace time-stamped monitoring, instrument-class review, utility investigation, or equipment manufacturer guidance.
Power quality symptoms can come from facility loads, utility events, equipment settings, grounding issues, or normal equipment sensitivity, so the worksheet preserves the evidence path.

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

Use this chart as a field record; verify IEEE power quality practices, utility requirements, equipment manufacturer limits, instrument data, adopted NEC requirements where applicable, and AHJ or facility requirements before corrective action.

How to use this chart

1Choose the symptom laneStart with the calculator analysis type so voltage, frequency, harmonic, flicker, and interruption results do not get mixed.

2Record event contextWrite where, when, and how the measured values were captured, including the affected equipment and operating state.

3Route the follow-upUse the worksheet to decide whether the next step is repeat monitoring, harmonic review, utility contact, or equipment manufacturer support.

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

Capture inputsDocument nominal voltage, measured voltage, frequency, THD, harmonic current, flicker severity, interruption duration, and event time as applicable.
Capture result labelRecord the calculator classification or severity label without turning it into a standalone diagnosis.
Capture evidence needsList the measurement interval, instrument, affected load, utility point, equipment documentation, and facility contact needed for follow-up.

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

Treating one calculator classification as a power quality diagnosis without time-stamped measurement context.
Mixing voltage sag, harmonic distortion, flicker, and interruption symptoms without documenting which calculator mode produced each result.
Blaming the utility or the load before recording the measurement point, event duration, affected equipment, and repeated-event pattern.

Frequently asked questions

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

Can one voltage reading diagnose a power quality problem?

No. A single reading can start the worksheet, but recurring or sensitive-load problems usually need time-stamped measurements and review of the affected equipment.

Why connect symptoms to calculator modes?

Voltage, frequency, harmonic, flicker, and interruption results use different inputs, so the worksheet preserves which screen produced the label.