NEN 3140 vs. NEN 3840 — where does low voltage stop?

Every designation, every exam, and every guide on this site deals with low voltage (LV) — that is the scope of NEN 3140. As soon as an installation or a work activity exceeds the LV boundary, a different standard applies: NEN 3840. Confusion on this point leads in practice to a dangerous assumption: that a VP or VOP designation valid for low voltage would also be valid for high-voltage work. That is not the case.

The voltage boundary

Standard	Scope
NEN 3140	Operation of electrical installations and equipment up to and including 1000 V AC / 1500 V DC.
NEN 3840	Operation of electrical installations and equipment above 1000 V AC / 1500 V DC.

This boundary matches the international IEC definition of high voltage (above 1000 V AC / 1500 V DC) and is the same boundary used by the Dutch Working Conditions Act (Arbowet) and NEN-EN-IEC 60364 (NEN 1010) for "low voltage".

What does this mean for VP/VOP designations?

A VP or VOP designation under NEN 3140 is valid only for work activities within the LV scope.
For work on or near high-voltage installations (e.g. MV/HV switchgear, own transformer substations, HV cables), a separate designation under NEN 3840 is required — with its own training, its own exam, and its own competence. This does not follow automatically from a NEN 3140 designation, regardless of how much experience someone has with low-voltage work.
Employers who manage both LV and HV installations often have combined NEN 3140/3840 training tracks — but these remain two separate designations on the designation document, not one combined competence.

Practical trigger points

Situations in which an installation or a part of it falls under NEN 3840 instead of (or alongside) NEN 3140:

An on-site medium-voltage transformer or switching station (common in larger industrial or agricultural businesses — see also the greenhouse installation examples in the §705 guide). From the point where the MV side begins (before the transformer), NEN 3840 applies; the LV side after the transformer again falls under NEN 3140. The transformer itself and the MV switchgear are NEN 3840 territory.
HV cable routes crossing a site, even if the end user only operates LV equipment.
Work near (not necessarily on) an HV installation — the approach-zone rules are stricter than for LV (see the guide on danger/approach zones).

Why this matters for VP/VOPs

A VP who holds only a NEN 3140 designation may not provide a risk inventory, inspection, or designation for HV installations — that requires a separate NEN 3840 VP. Recognizing this boundary is therefore not merely a formality: it determines whether someone is qualified (and insured) to carry out a given task.

Common mistakes

Assuming "a lot of LV experience" replaces HV competence — the two standards require separate, specific training and examination.
Treating the MV side of an on-site transformer substation as "just part of the installation" — everything before the transformer (on the MV side) falls under NEN 3840, not under the building manager's NEN 3140 designation.
Applying NEN 3140 approach distances to HV work — the safety distances and zoning for high voltage are larger and structured differently than for low voltage.