Standard cables provide powerful electrical connections, but it’s crucial to reinforce all your wiring in locations with high electromagnetic interference. For offices, retail spaces and industrial buildings, you must invest in cable shielding. 

Cable shielding is a great way of ensuring a powerful electrical connection without interruptions. These cables are designed to bypass any technical interference and improve signal integrity. If you plan to switch to shielded cables, here are some essential things to remember. 

What Is A Shielded Cable?

Cable shielding or screening protects your wiring from electromagnetic interference in a specific environment. EMI activity typically happens in the form of noise. 

Some common sources of EM interference include fluorescent lighting, generators, lift motors, air conditioners, compressors and photocopiers. 

Regular insulating conductors are placed in a standard conductive layer in every shielded cable. On top of this component, a special protective shield is added to give it the screening ability. 

This shielded layer is what sets it apart from other variants. The shielded elements are typically made from three different materials. These include:

• Braided or strands of copper
• Conducting polymers
• Spiral copper tape

Why Is Cable Shielding Important?

Industrial environments such as factory floors and assembly rooms are generally electrically noisy areas. Electrical noise, either through electromagnetic interference or radiation, can severely disrupt signals and break down equipment operations.

While insulation is excellent at protecting wires from abrasion, scraps, moisture and other physical damage, it’s ineffective against EMI. Shielding is required to bypass the effects of EMI through leakage and interference.        

Apart from surrounding equipment, cables are also a primary transfer source for EMI. If the cable is a source, it conducts noise to other equipment or acts as an antenna that dispels noise. 

The cable is a receiver; it can pick up EMI radiated from other equipment. Shielding repels electric noise in both ways for an uninterrupted connection.     

How Does Cable Shielding Work?

The best way to get rid of EMI in cables is through shielding. The shield surrounds the inner conductors or signals and protects your wiring in two ways. 

First, it can reflect the noise causing interference. Alternatively, it can pick up the energy and conduct it into the ground. Either way, the shield takes the EMI from the conductors without disrupting any signal connections inside the cable. 

Shielded cables come in various screening levels, offering a wide range of effectiveness. The amount of shielding your cable needs depends on multiple factors, including the electrical environment the cable is placed in, the cost of the cabling, its weight, diameter and flexibility. 

Shielded cables are important for reducing and insulating current from electrical noise or ambient EMI typically found in engineering, industrial or manufacturing locations.       

In general, you must use shielded cables in environments with high electrical power levels subject to electronic interference. 

What Is Electromagnetic Interference (EMI)?

EM interference refers to electrical voltages and currents commonly occurring in any environment. EMI disrupts signals outside cable networks in televisions, cell phones or AM radios. This can be either natural, artificial or inherent.

Natural EMI 

This type of electrical noise is caused by lightning and thunderstorms. Other causes include rain particles, snow storms and solar radiation. Naturally occurring EMI causes fewer problems with modern electrical equipment than their older counterparts. 

Manmade EMI

Unnatural or manmade EMI is caused by various types of electronic and electrical equipment. These include motors, transmitters, vehicle ignitions, power lines, generators, mobile phones, different light systems, etc. In conclusion, artificial devices are the central cause of this type of EMI, which can degrade power and data processing systems. 

Inherent EMI

Inherent EMI refers to the electric noise created inside electrical equipment. In some systems, the thermal movement of electrons flowing through a circuit makes white noise, which is electromagnetic interference. Even some cables produce this type of noise, disrupting signals without shielding.

What Are The Two Different Types of Cable Shielding?

There are two common ways to shield cables, each of these methods having benefits. The two methods include foiling and braiding. Here’s a closer look at how they work.

Foil Shielding in Cables

In foil-shielded cables, a thin layer of aluminium, commonly attached to a polyester carrier, adds strength and durability to the equipment. This metal provides complete coverage of the surrounding conductors, making it an excellent option for screening. 

However, the thinness makes it challenging to work with, especially in locations that need a connector. In this scenario, you can use a drain to ground the shield. Foil shield cables are great for busy office and commercial environments.         

Braided Shielding in Cables

A woven mesh of tinned or bare copper wiring is used in braided shielding. The braiding provides low resistance when grounding the cable and is much easier to terminate through soldering or crimping when you attach a connector. 

However, braided shielding doesn’t provide complete coverage because it creates small gaps in coverage. Typically, the effectiveness of this style depends on the tightness of the weaving. 

Braided shielding generally provides between 70% to 95% coverage. If the cable is stationary, 70% is sufficient enough to do the job. In fact, a higher percentage of covering doesn’t always guarantee more shielding effectiveness. 

Since braiding uses copper, it's a much better choice for cable shielding. Copper has a higher conductivity rate than aluminium, making it far more effective at intercepting EMI. 

However, this can add cost and size to the cable, so consider this factor with braided shielding. Due to their higher effectiveness, braided-shielding cables are better suited for an industrial environment. 

Multiple Shielding Cables

For extremely noisy areas, it’s recommended that you use multi-shielded cables. This means using cables with both foil and braid shielding. 

Individual strands are sometimes shielded with foil in multiconductor cabling to protect pairs. The overall cable is then shielded with a braid, foil or both. 

Protective Covering for Shielded Cables

Special protective coverings are installed on the ends to ensure that shielded cables work well without any damage. Hoods are the protective casing that houses the connectors and pinning in a cable. These are either made of metal or plastic. 

Metal hoods offer protection against EMI and radio-frequency interference at the termination site on the cable connector. Plastic hoods are commonly used with unshielded cable, so always look for a metal component. 

Shielded vs. Unshielded Cables

As mentioned before, cables can come with or without shielding. Aside from the physical difference between the two, shielded and unshielded cables differ in their installation and how they work within a system. In some locations, you can only use shielded cables. 

While some unshielded cables have a set of twisted wires to remove low-level EMI, they are unsuitable for industrial environments where a lot of power is used. Unshielded wiring is commonly used in:

• Domestic properties
• Indoor areas with local network systems.
• Local cable systems in small to medium-sized offices. 
• Controlled industrial regions where cables are placed in metal conduits. 

Using Shielded Cables

On the other hand, shielded cables protect data and power paths from EMI degradation. They do so without any external component. 

Electrical noise and EMI disrupt electrical circuits through electrostatic coupling, induction or conduction. This disturbance interferes with a circuit’s performance and sometimes stops it from functioning completely. 

EMI can cause error messages in data computing machines or completely lose the data. Shielded cables remove the volume and intensity of electrical interference and any adverse effect on transmissions and signals. 

Shielded cables should be used in areas like:

• Heavy industrial settings and manufacturing plants
• Large data centres
• Airports
• Radio stations  

Important Guidelines for Cable Shielding

Shielded cables do a great job of removing any EMI, but there are several ways to maximise their efficiency. Here are some important guidelines to best use shielded cables.

• Make sure that the cable you choose has enough shielding for an application’s needs. A foiled cable may be adequate for installation in areas with moderate EMI. Only use braised or multi-shielded cables in heavily noisy environments. 
• Use a cable compatible with the equipment. Cables requiring excess flexibility or repeatedly wrapped around an object work well with braided shielding. Avoid using foil shielding here, as the continuous flexing can cause a tear in the foil. 
• Ensure the equipment that the cable is connected to is properly grounded. Use an earth-ground cable when needed and check the connection between the grounding point and the appliances. The noise level elimination depends on a low resistance path to the ground.
• Always ground the cable at one end because this removes the potential for noise-inducing ground loops.
• Some shielded cables have unnecessary design materials that do more harm than good. Opt for connector materials like cast zinc, metal-coated plastic or aluminium for better efficiency. 

Cable Shielding With Conduits

If you opt for an unshielded cable, you can still maintain signal integrity with electrical cable conduits. Cable or electrical conduits are plastic or metal tube structures holding essential electrical wires and cabling. These systems are often called trunking as well. 

The conduit’s structure can be rigid or flexible depending on where it’s installed. The purpose of a conduit is to protect wires from any hazards. You can also use them in unfinished or exposed indoor and outdoor settings. 

To fit various installations and demands, cable conduits come in various sizes, shapes, materials and styles. The most common material for the conduit is a metallic style. But you can also find conduits in plastic, fibre and fired clay. 

These structures are best for protection as they have a thick outer layer that protects your wiring. Here are three common types of conduits that are great at shielding cables.  

Electrical Metal Conduits

An electrical metal conduit is your best option for installing a rigid conduit system. This component has a thin wall structure of galvanised steel, commonly used as a non-flexible option. 

Even though this conduit comes under the rigid category, you can bend its shape with a conduit bender tool to fit any installation. The lightweight material is malleable enough to contort into any desired shape. 

Due to its manufacturing, electrical steel conduits can be applied in many locations. However, if an area experiences several physical damages, you should not use this material as it will get damaged easily and ruin your wiring system. 

You can use EMT conduits as an exposed or concealed wall installation. You can also use them on floors and ceilings. The metal material allows them to be embedded into concrete or buried in the ground. 

EMTs are ideal for indoor residential and light commercial installation. If installing them outdoors, you must assemble them with watertight fittings. 

Electrical metal conduits are connected with clamp-style fittings that slide onto the tubing. This configuration is secured with a set screw and locked into your desired area.      

Electrical Non-Metallic Conduit (ENT)

The electrical non-metallic conduit is great if you want a more flexible option. This conduit is made from pliable plastic tubing designed for placement in residential walls and concrete structures.

The ENT provides excellent protection against fire and moisture to keep all your wiring space. Despite these qualities, they are unsuitable for installation in exposed locations or any outdoor space where they might experience other elements. If you’re placing these conduits, use glued fittings. 

Flexible Metal Conduit (FMT)

FMT conduits have a spiral shape, making it easy to bend the conduit and simplifying installation. With this shape, you can add FMTs to walls and other structures. 

Flexible metal tubing is commonly used in exposed areas with a short run. For example, you would usually place them in water heaters. These conduits are often called liquid-tight metal conduits, depending on the outer sheath. 

The liquid-tight version has a plastic outer sheath, which makes it watertight. LFMCs are best used for outdoor wiring, air conditioning units, and other equipment.