Série 101 : Cordons de raccordement multibrins vs cordons de raccordement solides

Série 21 août 2019 / 101

You’ve likely heard copper patch cords referred to as being constructed of either “stranded” or “solid” cable, but do you know the difference and which to choose when? 

Just like the name implies, stranded four-pair cables are cables where each of the eight conductors of the four-pair cable are constructed of multiple “strands” of wires wrapped around each other, while solid cables are constructed with just one solid copper wire per conductor.

In a stranded cable, the wires that form the conductor are typically very thin wires that are wound concentrically in a helix to form the conductor (think of this like a rope). The construction of stranded cable is specified as two numbers – the number of strands as the first number and the gauge of the strand as the second number. Par exemple, un 7X32 (parfois écrit sous la forme 7/32) indique qu’il y a 7 brins de 32 fil AWG constituant le conducteur. In contrast, solid cable will just include one gauge number to indicate the size of the conductor.

But aren’t stranded and solid cables of the same category type the same gauge size? Yes, indeed they are. That’s because the final conductor size, regardless of whether it is made up of multiple strands or one solid conductor, are the same. En d’autres termes, un câble 24 AWG reste toujours un câble 24 AWG.

How Do they Differ?

The key physical difference between a stranded cable and a solid cable is flexibility. Stranded cables are much more flexible and can withstand more bending compare to rigid solid conductors that can fail if flexed too many times. And the more strands a conductor has, the greater the flexibility. Strand count can also impact cost – the more strands that make up a wire, the greater the cost. To keep costs down, stranded twisted-pair cable uses a high enough strand count to maintain proper flexibility but not so many that it creates a dramatic price difference. In other words, it’s a careful balance between cost and flexibility.

The construction of the cable also impacts termination. IDCs on jacks, patch panels and connecting blocks are made for solid cable. The individual conductors of a solid cable will hold their shape and properly seat in the IDC, while stranded conductors will typically break and can come loose over time. Solid wire is also considered more rugged and less susceptible to corrosion since it has less surface area than a stranded wire.

Another key difference is electrical performance. Solid cables are better electrical conductors and provide superior, stable electrical characteristics over a wider range of frequencies, offering lower susceptibility to high-frequency effects and lower DC resistance than stranded cables. That’s precisely why TIA standards allow a 20% increase in attenuation for stranded construction.

Which do I Choose?

When it comes to horizontal cable runs, there is no choice. Solid cable is the standard due to its better electrical performance and ability to punch down to IDCs . Where you do have a choice is with patch cords since most manufacturers offer both.

Because stranded cables are more flexible and can withstand bending, they make excellent patch cords for equipment connections and cross-connects where cables are frequently bent and manipulated. Patch cords are also shorter in length, so the higher resistance of the stranded construction is not typically a concern.

There is however a primary application in today’s LANs that warrants the use of solid patch cords – power over Ethernet. Lorsque le PoE est délivré sur des câbles cuivre à paire torsadée, une partie de la puissance se dissipe sous la forme de chaleur. Lorsque cela se produit, la température du câble peut augmenter. With their higher DC resistance, stranded patch cords are more likely to exhibit degraded transmission performance at elevated temperatures.

Bien que ce ne soit généralement pas un problème dans les espaces à environnement contrôlé comme le TR, une fois que vous commencez à brancher des appareils au plafond (pensez aux points d'accès sans fil, aux caméras de sécurité et aux lumières LED), les cordons de raccordement multibrins peuvent poser problème. A good rule of thumb is that if the environment is not temperature controlled and there’s not a lot of manipulation going on, choose a solid patch cord. If you do use stranded patch cords in uncontrolled environments, you’re better off keeping them short (about 5 meters or less). And if you’re skeptical, check it out yourself. Fluke Network’s DSX Series Patch Cord Test Adapters can be used to test copper patch cords or you can see the difference in channel testing.

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