What’s important (A3)?
- Current edition: NEN 3140:2011+A3:2019 (current at NEN).
- A3 clarifies arc-flash topics: procedures, PPE and determining incident energy at the workplace.
- Ensure risk-based approach: task risk assessment, permits to work, lock-out/tag-out and isolation; roles WV/Skilled/Instructed.
- Alignment with NEN-EN 50110-1 remains key; record inspection intervals in the management plan.
Safe work & authorisations
- Roles: Person in control (WV), Skilled Person (VP) and Instructed Person (VOP).
- Procedures: de-energised work, lock-out/tag-out, PPE, barriers and signage.
- Task/risk assessment (TRA/JSA), permit to work and release for service.
Management & periodic inspections
- Management plan with risk-based inspection intervals (environment, use, history).
- Measurements/tests appropriate to operations (e.g. RCD test, impedance; thermography where useful).
- Register findings, priorities and corrective actions.
Documentation & training
Maintain up-to-date schematics, component data, authorisations and work instructions; ensure training for staff and contractors.
Frequently asked questions
What is NEN 3140 about?
Safe operation of existing low-voltage installations: authorisations, procedures, management and periodic inspections.
How does it differ from NEN 1010?
NEN 1010: design/erection/initial inspection. NEN 3140: safe use and periodic inspections during operation.
Who may work on LV installations?
Staff with proper authorisation/competence (e.g. Skilled or Instructed Person) under company procedures.
How often to inspect?
Risk-based frequency defined in the management plan (depending on use/environment).