Electricity is invisible and can kill. Before you touch an installation, it must be made safe according to the five safety rules — and if it cannot, the strict L-AUS rules apply. Here is the life-critical basic discipline: the five rules, the voltage test, personal protective equipment, arc flash and first aid.
Introduction
The most dangerous thing about the electrical trade is that the danger cannot be seen. A bare cable looks the same whether it is de-energised or at 400 V. Therefore, personal safety is not an addition to the trade — it is a fixed working method that you follow every single time. The basic principle of DS/EN 50110-1 (operation of electrical installations) is that a risk assessment of electrical hazards MUST ALWAYS be carried out before a work task is started.
Three work situations
DS/EN 50110-1 distinguishes between three basic situations, and each has its own set of rules. By far most tasks should — and can — be performed in the first.
- 01Working without voltage — the system is made de-energised according to the five safety rules. This is the main rule and always first choice.
- 02Work on live (L-AUS) — work on or so close to live parts that there is risk of contact. Only permitted under stricter requirements and only when necessary.
- 03Work in the vicinity of live parts — where one works close to, but not directly on, electrical equipment (e.g. another installation beside it). Requires distance, shielding or supervision.
The five safety rules
If a system is to be made de-energised, it is done according to the five safety rules — and the sequence is mandatory. If you skip a step, the entire method loses its value.
- 011. Disconnect — isolate the system on ALL poles so it is galvanically disconnected from the supply. Not just switch off but break the connection (remove fuses, open breaker).
- 022. Secure against reclosure — lock the switch in the disconnected position, put up a warning sign and, if possible, take the fuses with you. A colleague must never be able to reconnect while you have your fingers in it.
- 033. Verify that the system is de-energised — measure all conductors with an approved voltage tester that itself is tested immediately before AND after against a known voltage source.
- 044. Work earth and short circuit — where required (especially high voltage and larger systems), the disconnected conductors are bonded to earth, so any reclosure or induced voltage is discharged.
- 055. Shield or cordon off nearby live parts — everything you cannot disconnect from but might touch is covered or marked.
The voltage tester — test before and after
Rule 3 rests on one tool: the voltage tester. But an instrument that is broken always shows "no voltage" — even on a live circuit. Therefore the method is always threefold: test the tester against a known voltage source (e.g. a live circuit or a built-in test source), measure on the circuit you want to work on, and test the tester again afterwards. If it still shows correctly, you can rely on the measurement. Use a two-pole voltage tester according to DS/EN 61243-3 — not a simple phase tester/screwdriver lamp, which only sees one conductor and easily gives false confidence.
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