Who May Perform Live HV Work?
Live HV working is the highest-risk activity on electric vehicles. DGUV 209-093 restricts it to a specific qualification tier – standard FHV qualification is not sufficient:
Level 3S
Live Working – Series Vehicles
Diagnostics and fault-finding under active HV voltage on production/series vehicles. Builds on Level 2S.
Level 3E
Live Working – Development
As Level 3S, additionally covering prototypes, test rigs and pre-production vehicles. Builds on Level 2E.
What Does Live HV Work Include?
Live HV work is defined by working in the immediate vicinity of energised conductors or components without insulation between the worker and the live parts. Typical activities include:
- Voltage measurements and diagnostics on active HV circuits
- Fault-finding under live conditions (e.g. oscilloscope measurements on HV components)
- Insulation resistance testing with the system partially energised
- Functional checks of HV contactors, BMS and cooling circuits under load
- Work on test benches where full de-energisation is not practicable
Mandatory PPE for Live HV Work
The employer must provide and maintain all PPE. Employees must inspect PPE before each use. Using damaged or expired PPE is prohibited.
- Class 1 insulating gloves (EN 60903) – rated to 7,500 V; must be tested annually and visually inspected before each use
- Face shield or arc-flash visor – protection against arc flash and flying particles
- CAT III/IV multimeter – measurement category matched to system voltage
- Insulated tools to EN 60900 – 1,000 V rated; never use standard tools near live HV
- Arc-rated protective clothing – where arc-flash risk assessment identifies a residual risk
Live Working vs. Voltage-Free Work
| Criterion |
Voltage-Free (Level 2S/2E) |
Live Working (Level 3S/3E) |
| HV system state | De-energised and locked | Energised |
| Min. qualification | Level 2S or 2E | Level 3S or 3E |
| Insulating gloves | Class 0 (≤1,000 V) | Class 1 (≤7,500 V) |
| Written risk assessment | Required (general) | Required (task-specific) |
| Face shield | Situational | Mandatory |
Does every workshop need live HV capability?
No. Most routine HV repair and service work – including replacing batteries, inverters and charging components – is performed in the voltage-free state after proper de-energisation (Level 2S). Live HV capability (Level 3S) is required for advanced diagnostics and development work where de-energisation would interfere with the measurement.
Can a Level 2S specialist supervise live HV work?
No. Both the person performing and the person supervising live HV work must hold Level 3S or 3E qualification. Level 2S authorises only voltage-free work and does not confer any supervisory rights for live HV activities.