L-AUS and AUS — work under voltage

Among the certificates you typically need to have in place before you can work independently as a supply operator are L-AUS and AUS. Both are about something that sounds like a contradiction: working on a facility while it is still live. Here you get the explanation for why it is sometimes necessary and what it requires.

§What does L-AUS mean?

L-AUS stands for low-voltage work under tension. This is work where there is direct contact with live parts in low-voltage systems while the system is still connected. Historically, one distinguished between AUS on the high-voltage side and L-AUS specifically on the low-voltage side — today both parts of the syllabus are already included in the second part of the basic course together with first aid.

§Why work under tension at all?

The short answer is: to avoid unnecessary operational shutdowns. Some facilities supply critical functions or many customers at the same time, and a disconnection would hit broadly even though the task itself is small. In those cases it can — under strict conditions and with proper training — be more appropriate to perform a limited task while the facility is still in operation than to shut down supply for many customers.

• 01The person must be at least 18 years old
• 02The person must be sufficiently qualified for that specific task
• 03Insulated tools and correct tested protective equipment must be used
• 04Work must be planned so risk is minimized before it starts

§Who oversees the rules?

Safety when working on and near electrical systems is regulated by the electricity safety law with associated regulations which the Safety Authority administers and oversees. The rules build on the European standard EN 50110-1 on the operation of electrical installations which describes the basic principles for safe work with and near live electricity.

§From historical watershed to common standard

Previously, the regulations made a sharper distinction between AUS work on the high-voltage part of a system and L-AUS work on the low-voltage part. Today, the regulations are collected under the common European standard EN 50110-1, but the division into the concepts continues in everyday language use because the tasks and concrete requirements for protective equipment and tools still differ depending on whether work is being done at low or high voltage.

For you as a student it means you will already in the second part of the basic course be introduced to the concepts together with first aid and basic fire fighting — the three skills that together cover the most serious risks in the trade. Later in the main course you build on this basic understanding as you work with increasingly higher voltage levels from 10-20 kV in main course 1 to 60 kV in main course 2.

§Preparation is half the work

In practice, preparation often takes more time than actual execution when a task involves work under voltage. Before the task begins, it must be clarified what the actual task is, which protective equipment and which tool it requires, and who has overall responsibility for the system while the work is going on. This systematisation is not bureaucracy for bureaucracy's sake — it is the very reason why work under voltage can be carried out safely, year after year, without serious accidents.

As an apprentice you will experience that this particular part of the trade takes up a lot in the teaching long before you yourself stand with the task in hand. It is intentional: the more thoroughly the preparation is ingrained as a habit already while you are learning it the less likely it is that you will later in your career skip a step because a task feels routine.

“To work under voltage is not a matter of courage — it is a matter of training preparation and knowing your own limits.”