What is NEN 3140?
NEN 3140 is the Dutch standard for the safe operation of low-voltage electrical installations and electrical work equipment, meaning systems up to and including 1000 V AC or 1500 V DC. It describes how an organisation safely operates, inspects, maintains and modifies existing installations, who is authorised to do so and how the work is organised. NEN 3140 is the Dutch supplement to the European standard NEN-EN 50110-1 and, in practice, is how employers meet the duty of care under the Dutch Working Conditions Act for electrical work.
Whereas NEN 1010 covers the design and installation of an electrical system, NEN 3140 focuses on the safe use and management of that installation throughout its entire service life.
🧱 Which installations and activities does NEN 3140 cover?
NEN 3140 applies to all work on, with or near low-voltage electrical installations. The standard uses the concept of operation (bedrijfsvoering), which amendment A2 of 2018 broadened: it covers not only operating, switching and maintaining, but also installing, inspecting and documenting.
As a result, nearly all electrical engineering in a factory falls within its scope:
- Fixed installations - main distribution boards, sub-distribution boards, MCCs, lighting, wall sockets and fixed wiring
- Machines and controls - control cabinets, PLC panels, electric drives and variable frequency drives, power supplies and emergency stop circuits
- Electrical work equipment - hand tools, cable reels, extension leads and measuring instruments
Above 1000 V AC or 1500 V DC, for example on the medium-voltage side of a site’s own transformer substation, the sister standard NEN 3840 applies. A designation under NEN 3140 gives no authority there.
🔄 How does NEN 3140 relate to other standards?
NEN 3140 does not stand alone. It is part of a chain of standards that together cover the life cycle of an electrical installation.
| Standard | Subject | Phase |
|---|---|---|
| NEN 1010 | Design, installation and initial verification of low-voltage installations (Dutch implementation of IEC 60364) | Design and installation |
| IEC 60204-1 | Electrical equipment of machines | Machine building |
| IEC 61439 | Low-voltage switchgear and controlgear assemblies | Panel building |
| NEN-EN 50110-1 | European base standard for the operation of electrical installations, including the five safety rules | Use and management |
| NEN 3140 | Dutch supplement to NEN-EN 50110-1 for low voltage | Use, inspection and maintenance |
| NEN 3840 | Dutch supplement for high voltage | Use and management above 1000 V AC |
| NEN-EN 50699 | Recurrent testing of electrical equipment | Use |
The version used in practice is the consolidated NEN 3140:2011+A3:2019. After a piece of work equipment has been repaired, NEN-EN 50678 applies to verifying its protective measures.
👷 Which roles and authorisations does NEN 3140 define?
The core of NEN 3140 is that everyone who works with electricity holds an appropriate written designation (aanwijzing) from the employer. That designation is based on training, experience and knowledge of the specific installation.
| Role | Dutch abbreviation | Responsibility |
|---|---|---|
| Person responsible for the installation | IV | Ultimately responsible for the safe operation of an installation; sets inspection frequencies and work procedures, among other things |
| Person responsible for the work | WV | Holds direct responsibility for safety at the work site during a specific job |
| Skilled person | VP | Has sufficient training and experience to assess risks independently and carry out electrical work |
| Instructed person | VOP | Has been instructed to carry out defined tasks safely, such as simple measurements or resetting a protective device |
| Ordinary person | – | Holds no electrical designation; works only under supervision or operates simple, safely enclosed parts |
Since amendment A2, splitting the role of the person responsible for the installation across several people must be justified by necessity and documented. That keeps it clear at all times who is accountable for an installation.
🔧 How do you work safely under NEN 3140?
NEN 3140 distinguishes three working methods: dead working, working in the vicinity of live parts and live working. Dead working is always preferred, and it follows the five safety rules from NEN-EN 50110-1:
- Disconnect completely - isolate the installation from all sources of supply
- Secure against reconnection - with a lock and tag in line with Lock-out Tag-out
- Verify the absence of voltage - with a tested voltage detector on all poles
- Earth and short-circuit - where required, especially with back-feed or stored energy; see Earthing
- Protect against adjacent live parts - shield or fence off anything that remains energised
Around this sits a fixed organisation: a work permit for high-risk jobs, an LMRA just before starting, suitable personal protective equipment such as arc-rated clothing and face protection, and reporting incidents and near misses through incident management. Live working requires a specific designation and suitable insulated tools.
🏭 What does NEN 3140 mean for OT environments?
In OT environments, automation engineers, PLC programmers and technicians work in energised cabinets every day. A few practical points:
- Opening a cabinet is electrical work - anyone who opens a control cabinet containing live parts to replace a PLC module or patch a network cable is working in the vicinity of live parts. As a rule this requires at least a VOP designation, even if the task itself looks like “IT”.
- Residual voltage - variable frequency drives keep dangerous voltage on their DC-link capacitors for minutes after switch-off; the manufacturer specifies the waiting time.
- Multiple supplies - control voltage, UPS units and external 24 V supplies can still be live while the main switch is off.
- Remote restarts - with remote maintenance a supplier could start a machine while someone is working on it. Lockout and clear arrangements in the work permit prevent that.
- ATEX zones - in potentially explosive atmospheres, the requirements of ATEX and IEC 60079 come on top of NEN 3140.
🔍 How does a periodic NEN 3140 inspection work?
A periodic inspection demonstrates that an installation is still safe. A typical approach:
- Risk assessment - the person responsible for the installation sets the inspection frequency based on a documented risk assessment and the RI&E. In industry the interval often lies between one and five years, shorter where moisture, dust or vibration are present.
- Check documentation - up-to-date drawings, schematics and the installation logbook.
- Visual inspection - damaged cables, missing covers, overheating, labelling and accessibility of cabinets.
- Measurements - including insulation resistance, continuity of protective conductors, earth fault loop impedance and the operation of residual current devices.
- Reporting and repair - defects are classified, repaired and re-checked; recording them in the CMMS helps with follow-up.
| SCIOS scope | Subject | Basis |
|---|---|---|
| Scope 8 | Electrical installations | NEN 3140 |
| Scope 9 | Electrical work equipment | NEN 3140 |
| Scope 10 | Electrical equipment, fire risk | NTA 8220 |
| Scope 12 | Solar power installations | Various applicable standards |
An inspection by a SCIOS-certified company is a generally accepted way to show that the employer meets its duty of care. Many insurers have also written the Scope 10 inspection into their fire insurance policy conditions; NTA 8220 was developed together with the electrical engineering sector and the insurance industry.
🔐 How does NEN 3140 fit with safety policy and audits?
NEN 3140 is about the electrical safety of people, not about information security. In an integrated security and safety policy the two do sit side by side: the same cabinets contain PLCs and network switches that also fall under the cybersecurity policy, and physical access control to switchgear serves both goals. During an audit or a visit from the Netherlands Labour Authority, inspectors look at designations, inspection reports, work permits and the follow-up of defects. This fits with ISO 45001 for organisations with a certified occupational health and safety management system.
❓ Frequently asked questions
Is NEN 3140 a legal requirement?
NEN 3140 is not literally prescribed by law. The Dutch Working Conditions Decree (articles 3.4 and 3.5) does require safe electrical installations and safe work on them, and NEN 3140 is the accepted way to demonstrate that. Anyone who chooses a different method must be able to prove that it is at least as safe.
How often must an installation be inspected under NEN 3140?
NEN 3140 does not prescribe a fixed period: the person responsible for the installation sets the interval based on a risk assessment. In industrial environments this is usually between one and five years. After changes to or damage of the installation, an additional inspection is advisable.
What is the difference between a VP and a VOP?
A skilled person (VP) has the training and experience to assess electrical risks independently and to carry out electrical work. An instructed person (VOP) has been instructed for defined tasks and works within the limits of the designation. Both designations under NEN 3140 apply to low voltage only.
What is the difference between NEN 3140 and NEN 1010?
NEN 1010 contains the requirements for the design and installation of a low-voltage installation, including the initial verification at handover. NEN 3140 then governs safe use, periodic inspection and work on that installation. Together they cover the whole life cycle.
Who issues a NEN 3140 designation?
The employer designates employees in writing, usually on the advice of the person responsible for the installation. The designation states for which installations and activities someone is authorised and is based on training, experience and knowledge of the installation. When someone changes role or installation, the designation must be reassessed.
Does NEN 3140 also apply to tools and extension leads?
Yes, NEN 3140 also covers electrical work equipment such as hand tools, cable reels and measuring instruments. For recurrent testing of that equipment, NEN-EN 50699 is used alongside it. After a repair, NEN-EN 50678 applies to verifying the protective measures.
📌 In summary
NEN 3140 is the Dutch standard for the safe operation of low-voltage installations and work equipment: it defines who is authorised, how work is done safely and how often an installation is inspected.
Where NEN 1010 governs installation, NEN 3140 safeguards safety during use. For OT teams that means a designation before you open a cabinet, the five safety rules for every job, and a risk-based inspection whose findings are demonstrably followed up.