Voltage quality, flicker and sags

Distinguish an internal circuit/neutral/load problem from a grid event before replacing appliances or adding sensitive equipment.

VERT / GREEN

Log time, duration, affected circuits and large loads starting when lights vary.

JAUNE / YELLOW

Repeated flicker can be linked to rapid voltage variations or a local load; the source must be located.

ROUGE / RED

Burning smell, suspected neutral fault, severe abnormal voltage, arcing or multiple circuits affected: shut down/get service as appropriate.

Guided triage

Variation when motor startsDocument load/circuit and check starting voltage drop.Multiple circuits vary togetherCheck main supply/neutral and contact utility when indicated.Sensitive electronicsAssess supply quality/protection instead of random surge strips.Event logLog events to correlate grid, weather and loads.

Tools / data

Meter/logger by qualified person
Load event log
Affected circuits

What the professional checks

Separate utility/internal cause
Test voltage/neutral/connections
Assess equipment protection

Official sources

Hydro-Québec — caractéristiques basse/moyenne tension

Source check / vérification: 2026-08-22. Triage et planification seulement; les travaux réglementés restent aux professionnels requis.