Why are power lines twisted

Soldering cables - why it is better not to do this with stranded wires

by your electrician

Working with electrical systems, even in the low voltage range, is dangerous. Therefore, many safety standards apply to professional electricians, which also serve to ensure the compatibility of products and systems.
But also do-it-yourselfers and those who want to become one should adhere to the applicable regulations in order to minimize the risk. A literally hot topic here is connecting wires and cables with plugs, because improper work here not only leads to short circuits, but often also to fires.
Almost every third fire in Germany is caused by electricity. This is probably why the German Institute for Standardization (DIN) has banned the soldering of cable ends, among other things.
But what exactly is DIN saying here and how should you work instead?


Solder the cable or not? - The rule

The exact title of the relevant standard is VDE 0100-520. The directive to avoid soldered stranded connections is hidden deep in its subsections.
In order to explain: A strand is the term used to describe the conductors in a cable, which consist of a strand of many fine copper wires - this keeps the cable flexible. When connecting a cable with a plug, for example, the jacket and insulation are removed and the bare strands are connected to terminals. Soldering these strands causes the conductor cross-section to change, which also affects the flow of current. Individual wires can also come loose and stick out to the side. This can lead to short circuits in neighboring contacts.
Even without soldering, bare strands should not be pressed into a screw terminal (exception: elevator, spring-loaded or cage terminals).
Twisting the wires for easier insertion into the terminal is also inadvisable, since the conductor cross-section is also changed here.


Solder the cable or not? - So how do you work properly?


Regardless of whether you are a professional or a beginner, they are the right solution for connecting cable ends End sleeves.
These are small metal sleeves with everted collars that are pushed over the bare strand. Then it is crimped with pliers, that is, squeezed, until a solid conductor is created, if possible without empty spaces between the wires, because heat can build up here.
Here, too, the wires should not be twisted / twisted beforehand! Instead, you should pay attention to the correct fit of the ferrule.

The resulting, usually square conductor can then be simply clamped on without soldering. Wire end sleeves are available from RS Components, for example.

Having the right tools is also important when working with wire joints. The mentioned crimping pliers ideally have different sized squeezing chambers so that the sleeve holds firmly and airtight.
While a cutter knife is sufficient to remove the cable jacket, suitable wire stripping pliers are recommended for stripping, because a knife quickly cuts off individual wires from the strand and thus impairs its conductivity.
As always, safety comes first when working with electrical systems, therefore never work with cables that are live and, if in doubt, ask the specialist!

Filed Under: BasicsTagged With: soldering cables

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