Understanding The Purpose Of Drain Wire In Shielded Cables

If you’ve ever bought a shielded ethernet cable, you’ll see that there’s another piece you may not be familiar with. This extra strand sticking out of the cable is known as a drain wire. Drain wires work a particular purpose in shielded cable, and it’s essential to understand what they are.

A drain wire is the uncovered, stranded wire you find interleaved with the covering foil inside of shielded cables. This cable is an important element in facilitating the cable’s operation. Drain wires are employed in cables in combination with a metallic shield to secure adequate grounding. The drain wire helps to complete an electrical circuit from the shield and transport unwanted electrical noise to the ground away from the circuit. The drain wire is connected to the ground and is in contact throughout its length with the metallic side of the protecting tape. It would be complicated to connect the tape with an earth terminal without making use of a drain wire.

Understanding The Purpose Of Drain Wire In Shielded Cables

The drain wires are typically tinned copper conductors. The small coating allows preventing dissimilar metal reactions between the copper conductor and an aluminum screen. Instrumentation wires needing electromagnetic protection or for use in intrinsically safe circuits are examples of wires with drain wire in their structure.

Let’s take a look at how the drain wire helps in the performance and functioning of shielded cables:

Purpose of Drain Wire in Shielded Cables

  1. Allowing for Effective Grounding: The drain wire allows a continuous, low-resistance connection to the cable’s metallic protection, ending in very effective grounding.

The wire remains in contact with the metallic side of the shielding tape all through the body of the cable. That puts the drain wire in an excellent position to connect a shielded cable to its ground terminal.

What this means for the cable is that it is adequately protected against electrical surges that unavoidably happen from time to time. Any excessive electricity finds a pathway through the drain wire into the ground without causing harm to the machines connected to the wire.

  1. Removing Unwanted Electrical Noise: The metallic protection of the cable can only be genuinely efficient if there is a way to complete its circuit within the cable. The drain wire is an essential part of creating this circuit, which subsequently enables for undesired electrical noise to be redirected to the ground.

This kind of electrical noise can create considerable damage to electrical devices if allowed to continue unchecked. Video images are damaged by the noise, showing up as blurry or with stripes all over the screen. Audio can incorporate buzzing and humming noises. Complete digital networks can be affected and forced into a shutdown. Electrical measuring instruments can show the wrong reading.

For all these reasons previously mentioned, it is imperative to cancel electrical noise as completely as possible, and this is accomplished in shielded cables with the help of drain wires.

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Jessica Cardona

  1. Preventing Metal Reactions: Tinned copper conductors are regularly utilized to build drain wires. This kind of tin coating blocks reactions from happening between the copper conductor of the cable and the aluminum screen next to it.

The lack of such a reaction means that shielded cables can be used for a much longer time. Usually, when two reactive materials are placed next to each other inside a wire, the combination of heat and electricity inside the wire can produce a chemical reaction that destroys the wire’s insides and reduces its life cycle.