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Working with electricity

Most accidents with electricity happen due to the incorrect design of installations, working on installations with inadequate material or because the persons concerned do not have the necessary knowledge, training or experience. On this page pay attention to managing risks involved when working with electricity.

What do I need to look out for with electricity?

Protect yourself from electrical risks by obeying the following rules.

  • Modifications to electrical installations (and equipment) may only be performed by authorised personnel (qualified persons, QP).
  • Every object should be constructed in such a way that contact with live voltage is impossible (cables, plugs, casing).
  • If working with 'open' conducting parts is unavoidable (for example, during a repair) then you must consult a qualified expert. The risk of electrocution must be effectively limited by cordoning off the area and using warning signs/signals.
  • If you have any doubts then check that the electrical equipment concerned is properly fused.
  • Never install heavy-duty safety fuses yourself. Always let a qualified person do this.
  • Use only approved tools (according to NEN 3140). In cases of doubt ask your supervisor or a qualified person.
  • Switches, plugs and multiple socket outlets that feel warm could be making poor contact or are overloaded; let a qualified person replace these.
  • The linking of extension leads is strictly prohibited.
  • Extension leads, et cetera may not lay on the ground due to the risk of somebody tripping over them and the potential risk in the event of leakages.
  • Leads and plugs must not be damaged.

Earthing, what do I need to look out for?

Attaching an earth wire can prevent external parts from becoming charged.

  • Each new experimental object must be checked for electrical safety by a qualified person.
  • Experimental objects, metal parts (frames, cable conduits, laser tables, gas pipes, etc.) must be visibly earthed.
  • Earth wires are either in a yellow/green sheath or are made of unprotected copper wire.
  • Water, gas and central heating pipes may not be used for earthing purposes.
  • In rooms with increased humidity all exposed metal parts must be visibly earthed.
  • Special measures must be taken for measuring equipment where earthing is difficult (due to 'earth loops'). These measures may only be effected by a qualified person.

How do I disconnect items from the power supply?

You may not work on a set-up or equipment without first disconnecting from the power supply. Therefore switch off the power first or get somebody else to do this.

Low voltage (to 24 volts)
Disconnect the cable attached to the chassis.

Mains voltage (230/400 volts)
You can disconnect from the power supply by pulling the plug out, switching off the isolating switch or removing the safety fuses (and taking these with you). Always leave a warning behind that this part must remain disconnected due to work being performed.

High voltage

  • Alternating current: > 1000 V effectively between two phases or > 600 V between one phase and the earth
  • Direct current: > 1500 V between two poles or > 900 V between one of the poles and the earth

In the case of high voltage the work is always entrusted to a qualified person. The power supply is disconnected in the same way as for ‘mains power’. However, switching off a piece of equipment does not guarantee that there are no live parts. The qualified person will discharge live components by applying a clearly visible earthing with an earth stick.


Installations and equipment must regularly be subjected to an electrical safety test.

The Inspections methods are described in the NEN 3140 standard. This standard focuses on safety (e.g. earthing) and limiting the fire hazard (due to poor contacts).
Experimental objects must also satisfy the NEN 3140 standard.
Wall sockets and extension leads must be checked regularly. The same applies to tools.

Confidental Infomation