Drivers fail on one phase, lights flicker on others.
Learning Track · Module 7: Failure library · Step 49 of 101
| Symptom | Sudden high voltage on one phase and low voltage on another. Many drivers on the high phase fail at once. |
|---|---|
| Cause | A broken or loose neutral at the cabinet, in a cable joint, or in the supply. |
| Check | Measure phase-to-neutral voltage on each phase. Measure neutral current. Check neutral terminals and joints. |
| Fix | Repair the neutral. Replace damaged drivers. Check the full circuit before you restore it. |
| Prevent | Alarm on voltage outside limits. Tighten neutral terminals at each visit. Balance the load across phases. |
Warning
Treat as Critical. A lost neutral can also make exposed metal live.
Sources
- IEC 60364-6 Verification of low-voltage installations
- IEC 61643-11 Surge protective devices
- IEC 60598-2-3 Luminaires for road and street lighting
- Maker installation and maintenance instructions
Changes: 30 October 2026: First publication: guides for Europe, the Middle East, South Asia, and the USA; failure library; tender clause library; comparisons; tools; downloads. See the changelog. Found a mistake? Report it.