High-Voltage Safety, PPE and Emergency Response
What this domain covers
High-voltage safety is a pass/fail area: hazard recognition, PPE, lockout/tagout, verification of de-energisation and emergency response.
Core rules and concepts
- HV threshold: treat systems above 60 V DC or 30 V AC as hazardous; EV packs are commonly 300–800 V.
- Hazards: electric shock, arc flash, fire, thermal runaway, electrolyte burns, stranded energy and unexpected restart.
- PPE: Class 0 insulating gloves rated to 1,000 V, leather overgloves, face shield, arc-rated clothing, insulated tools and a CAT III meter.
- Isolation: follow the manufacturer's procedure, switch off, remove the service disconnect or open the HV breaker, lock and tag, wait the stated time, then measure for absence of voltage.
- Emergency: stop work, warn others, isolate if safe, use a suitable extinguisher or evacuate, and treat damaged batteries as a fire risk.
- Documentation: record the isolation, test values, PPE check and person responsible.
Worked example
A pack is rated 400 V. After removing the service disconnect, do you open the pack immediately? No. Wait the manufacturer's time, often 5–10 minutes, for capacitors to discharge. Then measure between HV+ and HV− and between each HV terminal and chassis. Only when readings are below the safe threshold is the circuit verified dead.
Traps that cost marks
Do not rely on gloves alone. Do not use AC-rated gloves for DC HV work. Do not cut an orange cable to check it. Do not assume switching off the ignition de-energises the pack. Do not re-energise while a colleague is working. Do not use water on a live electrical fire.