De-energised work under NEN 3140: the five safety rules

De-energised work means working on an installation that carries no voltage, after you have taken the measures to make it so. Under NEN 3140, this is the basis of every job on an installation. The five rules come from the European standard NEN-EN 50110-1, on which NEN 3140 is based. The law requires this in article 3.5, paragraph 3, of the Arbobesluit (Dutch Working Conditions Decree) : work on or near an installation may only be carried out when it is de-energised. Who may work is set out on the VP and VOP page. VP is a competent person (vakbekwaam persoon), and VOP is an adequately instructed person (voldoende onderricht persoon).

This page covers de-energised work. Live working falls outside its scope. According to NEN , in practice this is almost always a breach of the Arbobesluit. Article 3.5, paragraph 5, makes an exception for low voltage only when urgent need has been demonstrated, work has been expressly ordered and the installation is suitable.

The five safety rules

Work through the rules in this order. Do not skip any.

Number	Rule	What you do in practice
1	Isolate	Disconnect all sources that can supply the installation, including any back-up supply
2	Secure against re-energising	Lock the switch, hang up a sign or remove the fuse
3	Verify that there is no voltage	Measure with a suitable measuring device, and test the device on a known source first
4	Earth and short-circuit	Connect the parts you will touch to earth and to each other, where the situation requires it
5	Shield nearby live parts	Cover the live parts that are still nearby

The wording in the table is a simplified version. The exact text is in NEN-EN 50110-1 and NEN 3140, which you have to buy. Take the wording from the standard into your own working method.

The rules are the same for everyone. What differs is who carries them out, a VP or a VOP within their instructions, and who has recorded the working method.

Example: replacing a group in a distribution board

This is a fictional example. A technician replaces a circuit breaker in an office distribution board. He works as follows:

He tells the work responsible person what he is going to do and where.
He switches off the main switch and checks that there is no back-up supply.
He locks the main switch and hangs up a sign with his name and the date.
He measures with a voltage tester to confirm the group is de-energised, and he tests the tester on a known source first.
He does not earth and short-circuit. His working method states that this is not needed for this low-voltage group, because no source can re-energise it.
He covers the adjacent groups with an insulating sheet.
He replaces the switch and checks the connection.
He only switches the main switch back on once the work responsible person has released the board.

He records each step on the work form. That form is the proof that the working method was followed.

Common mistakes

Switching off only the main switch and not locking it. Someone can switch it back on.
Not measuring, and trusting a colleague’s word instead.
Forgetting a back-up supply, for example an emergency generator or a second connection.
Not testing the tester before you use it.
Not recording the working method, so you cannot later show how the work was done.

What does an auditor or inspector want to see?

A recorded working method that lists the five rules in order.
Designations for the people who carry out the work, see designating VP and VOP.
A role for the work responsible person and the installation responsible person, see IV and WV.
A link to your RI&E (risk inventory and evaluation), so that electrical work is recorded as a risk.

Frequently asked questions

May a VOP work de-energised?

That depends on their designation. A VOP works within the instructions of the VP or the work responsible person. If the task is not in the instructions, they may not do it.

Must I always use a work permit?

The standard requires a recorded working method. The form that takes, whether it is a form, a sign or an agreement made verbally, is up to your own procedure. Make sure that procedure is part of your designation or working method.

What is the difference from live working?

With de-energised work, you isolate the installation. With live working, the installation stays in operation. Under article 3.5, paragraph 5, of the Arbobesluit, that is allowed only in exceptional cases with extra measures. That falls outside this page.

Is this the same as inspecting the installation?

No. An inspection checks whether the installation is safe. This page is about how you work safely on the installation. See NEN 3140 inspection.

Checklist before you start

Is the work recorded in your working method or designation?
Is the work responsible person informed, and have they released the work?
Have you found all the sources that can supply the installation?
Do you have a suitable measuring device and a suitable tester with you?
Are the live parts nearby shielded?
Does everyone on the shop floor know that work is being done on the installation?

A yes to all six questions is the minimum. If you are unsure about any one of these points, do not start.