What is an Armoured Cable? Classification of Armoured Cables

What is Armoured Cable?

• An Armoured cable will with an extra protective layer which will isolate the core from unwanted cuts or damage.
• The armoured cable consists of an additional protective sheath that helps to protect the cable core.
• The armoured cable increases the life span of the cable to improve the performance, reliability, and safety of the cable core.
• The cable with extra sheath at an outside layer of protection provides tensile strength during the cable laying operation and protects while resting underground.
• The term Armour means protection or sheath
• Generally, in electrical power distribution, the armoured cable is a steel wire armoured cable designed for the main supply of 11KV to 33KV.

When to use Armoured Cable?

• Armoured cable is used when we require mechanical protection if there is damage to the cable. 
• It is used for underground cables through ducts.
• The selection of the right cable is very essential to ensure a safe long-lasting electrical installation.

Where to Use Armoured Cable?

Armoured Cable is used

• In a place where there may be accidental damage due to mechanical stress.
• When the cable requires to be buried underground directly for outdoor installation or in tunnels.
• In applications exposing physical damage,
• For earthing for equipment supplied by the cable.
• During installation, special care must be taken for the cables so that they should not be bent to a radius less than the minimum specified by the manufacturer.

What is a Single-Phase Armoured Cable?

• The Single Phase Steel Wire Armoured Cable is a type of electrical mains supply cable with different cores with Brown, Blue, & Green or Yellow colour cores, instead of the standard Brown, Black, & Grey.
• The steel wire armour under or below the sheath protects the core to make it ideal for extreme setting applications for industrial needs.
• This Single-Phase Armoured Cable can also be buried underground. 0fb578

• Core colours of Single Phase Steel Wire Armoured Cable are:
• Brown for the Live connection
• Blue for the Neutral
• Green and Yellow for the earth connection

What is Three Core Armoured Cable?

• Generally, in electricity transmission, this three-core armoured cable refers to steel wire armoured (SWA) cable.
• Three Core Armoured Cable is a hard-wearing power cable utilized to deliver the main supply to houses, and outdoor structures such as sheds and open yards. 
• This cable is composed of a set of insulated twisted brown, blue, green, and yellow copper wires in a black protective sheath.
• The most popularly used cable size is a 6mm

What is Four Core Armoured Cable?

• Four-core armoured cable is another type of electrical power cable to convey both low voltage and low current signals in single-phase systems.
• The four-core armoured cable includes three coloured insulated copper wires that are Brown, Blue or Green, & Yellow along with un-insulated wire of the same colours functioning as the protective armour.
• Four-core armoured cable is a multi-core polyvinyl chloride cable with steel wire armour SWA.
• This cable is used for wide applications, such as
• Underground power networks,
• Indoor and outdoor installations,
• The 4 core cable can also be used in three-phase circuits.
• Low voltage lighting
• Solar panels for both ground & roof mounting
• Low-transmission installations like extractor fans that are controlled by humidity detectors.

Classification of Armoured Cables

Wire-Braid Armoured Cable

• Wire braid armoured cable or basket-weave armour is used for light and flexible protection.
• Wire braid is manufactured in a similar to fibrous braid.
• The metal is directly combined over the cable as the outer covering.
• Generally, galvanized steel, copper, bronze, or aluminium are used to make the braid.

Steel Wire Armoured Cable

• Steel Wire Armour cable is shorted as SWA cable.
• It is suitable for high-drop areas.
• It resists external mechanical forces and extensive tension.
• Multiple core cable uses Steel wire armour to resist high pull loads.

Steel Tape Armoured Cable

• Steel Tape armour cable is shorted as STA cable 
• It is suitable for buried laying
• It resists external mechanical forces
• But this STA cable is not suitable for large tensile forces.

Aluminium Wire Armoured Cable

• Aluminium Wire Armoured Cable is shorted as AWA cable. 
• The nature of aluminium is non-magnetic there are no induced current signals in the armour due to the currents flowing in the main conductor
• Aluminium Wire armour is used in
• Electrical power networks
• Underground installations
• Outdoor and indoor applications
• Power  and control cables for cable ducts

Why are Armoured Cables used?

• Armoured cables are used in a variety of applications where the cable needs to be protected from mechanical damage.
• The armour on the cable helps to protect it from damage that might be caused by impact, crushing, or penetration.
• The armour also helps to protect the cable from moisture and other environmental factors that can cause it to degrade over time.
• In addition, armoured cables are often used in areas where there is a risk of electrical interference, as the armour can provide additional protection against interference.

Construction of Armoured Cable

Generally, the construction of an aluminium wire armoured cable or steel wire armoured cable consists of six portions.

1. Conductor (Stranded Copper)

• Class II stranded plain annealed copper conductor functions as a conductive material to convey electrical signals.
• A conductor such as copper is a good conductive element of electricity, and aluminium is a bad conductive element of electricity because it is weaker.

2. Insulation (Color Coded Cable)

• For high insulation, this cross-linked polyethene (XLPE) is recommended over polyvinyl chloride (PVC)
• Cross-linked polyethene (XLP or XLPE) is one type of insulation material with high insulation resistance, high dielectric strength with low dielectric constant.
• XLPE or PVC-XLPE is very soft and expensive with a better coating to provide high-temperature resistance and better water resistance,

3. Armour

• Steel or aluminium armour provides good mechanical protection
• It allows the cable to resist exposed mechanical stresses.
• Hence, the protection cable is not subjected to damage from external mechanical forces.

4. Bedding (Inner Sheath)

• The bedding is a protective layer to create a barrier between the insulation and the armour.

5. Sheath (Outer Jacket)

• The sheath provides a higher protection level to elemental parts of the cable held together.
• Cable sheath material degrades soon due to several reasons such as chemicals, excessive heat, or cold and ultra-violet radiation emitted by sunlight.
• But the black sheaths offer maximum UV resistance.
• Low Smoke Zero Halogen (LSZH) sheath is would be recommended in tunnels or in public areas.
• Some manufacturers include UV stabilizers and anti-termite additives in cable sheath material.

6. Voltage

• Voltage ratings of 600/1000V, 6.35/11kV, and 19/33kV.

Differentiate Steel Wire Armoured (SWA) Cable and Steel Tape Armoured Cable (STA).

Typically, steel is used as encapsulating material for cable; it may be in wire form or tape form.

Another material such as aluminium is also used for armouring, but steel is the most commonly used and is highly recommended.

Steel Wire Armoured cables

• Has the capability to resist general longitudinal tension.
• These cables are well suited for network cable, control systems, outdoor, and indoor applications, and cable ducting.
• Steel Wire Armoured cables are made by winding solid steel wires around the bedded cable in a spiral form.
• Its diameter ranges between 0.9mm to 3.0 mm.
• Steel Wire Armoured cables are more expensive than Steel Tape Armoured Cables
• Highly difficult to bend
• Steel Wire Armoured Cable has good mechanical protection and can be used for external use.
• It is a power and auxiliary control cable, designed for electrical mains supply

Steel Tape Armoured Cable

• can be buried directly or pipe laying, in common ground, tunnel, etc.
• Steel tape armouring uses 2 helically wound galvanised steel tapes, both wounded in the same direction.
• Easy to manufacture
• Cheaper than Steel Wire armoured cables
• It is a popular method for protecting fibre optic cables.
• The steel tape armouring method increases both strength and flexibility.
• It can be used in a corrugated fashion or interlocking fashion.

Cable Armour as an Earthing Function

• The metallic armouring provides good cable strength and high protective covering.
• Cable Armour can be a circuit protection conductor (CPC) and main protective bonding conductor.

Use of Armour for Earthing

The primary function of an armoured cable is that it provides overall strength

Armour can be used as a

1. Circuit Protective Conductor (CPC),
2. Main Protective Bonding Conductor, and
3. Earthing Conductor.

Use in Telecommunications

• In submarine communications, armoured cables are used for protection against damage by fishing vessels and wild aquatic lives
• In the olden days iron wire armouring is used to carry telegraphs, but now this iron wire is switched to steel

Some Useful Questions related to Armoured Cable

What is Armoured Cable?

The armoured cable is a common electrical cable with an extra protective layer to keep it away from unwanted cuts or damage.

What is an armoured cable used for?

Generally, armoured cables are used for power and auxiliary control cable and are known as Steel wire armoured cable.

• Mains supply electricity
• Cable and power networks
• Underground systems
• Outdoor and indoor applications
• Cable ducting

Difference between Shielded Cable and Armoured Cable

Shielding

• It is a metal layer between cables that conveys electricity.
• It is also known as the conductor.
• It is prepared from copper, aluminium, steel, or other conductive materials.
• It protects the cable from an invisible signal and current interference called electrostatic interference
• Shielding allows the cable to work with uninterrupted signals
• It works as noise insulation for the conductor

Armour

• The armour provides physical cable protection.
• Copper & Aluminium are used to make this metal layer
• Armour is strong and sturdy and it can be used in harsh environments.
• armour prevents the cable from being crushed to avoid physical damage.