Steel Wire Armoured Cable: Everything You Need to Know

Tue 20th Oct 2020

Steel Wire Armoured (SWA) Cable is a hard-wearing power cable designed for the supply of mains power. A staple of modern power distribution, it combines strength and durability, with engineers designing it to protect conductors in demanding environments where mechanical stress, impact and exposure are everyday realities. From infrastructure and construction projects to industrial facilities and utility work, SWA Cable plays a critical role in delivering safe, reliable mains power. Or, as most electricians put it… a pain in the ar… neck! Its tough protective layers are excellent for performance, but they can make stripping, dressing and gland preparation slow, awkward and physically demanding on-site. For installers, engineers and project teams working to tight deadlines, inefficient preparation isn’t just frustrating. It costs time and money! This blog shows you how to work more efficiently with SWA Cable, covering practical handling tips, preparation best practices and smarter tooling that makes your life so much easier. And SPOILER ALERT, there’s a purpose-built SWA Stripping Tool for electricians, engineers, contractors, construction managers and project managers waiting at the end.

What is SWA Cable?

Steel Wire Armoured (SWA) Cable is a power and auxiliary control cable designed for the mains supply of electricity. It serves as one of several heavy-duty protected electrical links in power distribution, alongside medium- and high-voltage options such as 11 kV and 33 kV cables.

Built with mechanical protection in mind, SWA Cable is a popular choice for outdoor and underground applications where durability is critical. Its steel wire armour helps prevent pinching and accidental damage, while the protective construction shields the inner cores from impact and environmental stress.

That protection comes at a cost, though. SWA cables are heavy and extremely difficult to bend, making handling and routing more demanding on-site. Installers most commonly use them for underground runs or for securing power cables to external walls using cable cleats.

You might also hear SWA referred to as Mains Cable, Armoured Cable, Booklet Armoured Cable or simply Power Cable. The term Power Cable, however, is broader and covers many cable types, including 6381Y, 6491X, NYCY and NYY-J.

And a quick note for our American audience: This article uses the British English spelling “Armoured” rather than the American English “Armored”.

SWA Cable Applications / Industries

You’ll find SWA Armoured Cables across a wide range of sectors, from transmission and power distribution to the renewable energy industry. They’re also essential in oil, gas, and petrochemical operations, as well as water treatment facilities and various transport systems.

In railway infrastructure, engineers typically use SWA Cables to deliver power to non-trackside areas. Meanwhile, 33 kV and 11 kV cables handle distribution between substations, with 33 kV cables preferred for longer-distance runs. Beyond railways, SWA Cables are trusted for both indoor and outdoor applications. This includes control systems, cable networks, underground installations, ducting setups, and general power distribution projects.

Using Steel Wire Armoured Cable as Earthing

Using the armour of SWA Cable to provide earthing or grounding for connected equipment is a topic of ongoing debate within the electrical industry. Technicians commonly refer to this function as the Circuit Protective Conductor, or CPC.

In practice, the CPC is usually provided in one of two ways:

Additional core within the cable – For example, using a three-core cable instead of a two-core (line and neutral) cable, with the armouring acting as the CPC
External earth wire – Running alongside the cable to provide the protective conductor function

The main considerations when using the armouring as a CPC are its conductivity relative to the cores, which drops as cable size increases. Reliability and Health & Safety issues are also important factors to consider. According to recent research and guidance from authoritative sources, a detailed analysis has concluded that, in most cases, the armouring is suitable to serve as the CPC under UK Wiring Regulations.

What is Earthing?

SWA Cable Components

The typical construction of a Steel Wire Armoured Cable includes:

Conductor: Class 2 Plain Stranded Copper (Cu) Conductor, complying with BS EN 60228:2005.
Insulation: Cross-Linked Polyethylene (XLPE) is widely used as insulation in power cables, offering excellent electrical performance and water resistance. It also keeps conductors and other metal components safely separated, preventing unwanted contact.
Bedding: Polyvinyl Chloride (PVC) is used as bedding to provide a protective layer between the cable’s inner and outer components.
Armouring: Steel Wire Armour (SWA) provides mechanical protection, allowing the cable to withstand higher stresses and making it suitable for direct burial and external or underground installations. The armouring is typically connected to earth and can also serve as the CPC, as mentioned above.
Sheath: The Polyvinyl Chloride (PVC) sheath binds all the cable components together while providing extra protection against external damage.

Steel Wire Armoured Cable (SWA) - Components

The construction of a Steel Wire Armoured (SWA) Cable varies depending on its intended application. For installations in highly populated or enclosed public areas, a Low Smoke Zero Halogen (LSZH) variant — known as SWA BS 6724 Cable — is required. This cable features LSZH bedding and a black LSZH sheath to minimise smoke and toxic gas in the event of a fire. Following the King’s Cross fire in London in 1987, which resulted in fatalities from smoke and toxic gas inhalation, authorities now mandate LSZH sheathing for all London Underground cables.

What Do BS5467 and BS6724 Stand For?

When it comes to protecting mains electrical connections in demanding environments, using reliable SWA Cables is essential. In the UK, choosing SWA Cables with BASEC certification to the BS5467 Standard ensures rigorous testing and quality checks for the product. The British Approvals Service for Cables (BASEC) grants this certification to cables that fully meet its exacting standards.

BS5467 covers low-voltage SWA Cables with EPR or XLPE insulation and a PVC sheath, confirming they comply with British construction and testing requirements. Electricians widely use these cables in general low-voltage applications where mechanical protection and reliability are priorities.

BS6724, on the other hand, specifies low-voltage armoured power supply cables with XLPE, EPR, or thermosetting polyolefin insulation and a Low Smoke Zero Halogen (LSZH) sheath. These cables are designed for use in public areas where reducing smoke and harmful fumes in the event of a fire is critical. Compared to BS5467 Cables, BS6724 Cables produce lower levels of smoke and corrosive gas when exposed to fire.

Mechanically, single-core BS6724 Cables are protected with Aluminium Wire Armour (AWA), which is non-magnetic and prevents magnetic currents inside the cable, while multi-core variants use Steel Wire Armour (SWA). The robust armouring makes these cables suitable for direct burial installations where there is a risk of mechanical damage. Additionally, BS6724 Cables must comply with the Construction Products Regulation (CPR) when used in fixed installations in buildings and other constructions.

Because cable standards can vary between countries, it’s always important to verify that you’re selecting the correct armoured cable specification for your particular project.

Cores

Multi-Core

Steel Wire Armour is used exclusively on Multi-Core Cables, which contain two or more cores:

2-Core SWA Armoured Cable carries live and neutral conductors for Class II and Double-Insulated appliances that do not require an earth connection.
3-Core SWA Armoured Cables include live, neutral and earth conductors, unlike 2-core cables. Three-core cables are designed for Class I or Single-Insulated appliances, which require an earth connection.
4-Core SWA Armoured Cable is ideal for low-voltage or low-current signal applications. It consists of four individually colour-coded copper conductors, which is why it’s called a four-core cable.
5-Core SWA Armoured Cable is most commonly used for low-voltage transmissions and typically features a three-phase line along with a one zero line for the power supply.
7-Core The primary purpose of SWA Armoured Cable is for low-voltage connections, typically up to a maximum of 50V DC. Each core consists of copper conductors enclosed within the steel armouring.

Single-Core (Aluminium Wire Armoured)

Steel Wire Armour (SWA) is suitable only for Multi-Core Cables. For Single-Core Cables, Aluminium Wire Armour (AWA) is the preferred choice. Electricians should avoid using Single-Core Cables armoured with Steel Wire or Steel Tape in AC circuits. This is because aluminium is non-magnetic, whereas steel wire or steel tape acts as a ferromagnetic enclosure, which can interfere with the circuit. For Single-Core armoured installations, Aluminium Armour is the recommended solution.

SWA Cable vs AWA Cable – Comparison Table

Feature	Multi Core Cable (Steel Wire Armoured)	Single Core Cable (Aluminium Wire Armoured)
Armour Type	Steel Wire Armour (SWA) used exclusively	Aluminium Wire Armour (AWA) preferred over steel for single core
Number of Cores	Two or more cores (2-core, 3-core, 4-core, 5-core, 7-core, etc.)	Single core
Typical Applications	– 2-Core: Live and neutral for Class II/double-insulated appliances – 3-Core: Live, neutral, earth for Class I/single-insulated appliances – 4-Core: Low-voltage/low current signals – 5+ Core: Low-voltage transmission, often 3-phase + neutral – 7-Core: Low-voltage connections up to 50V DC	Used for AC circuits where single-core conductors are required
Earth/Protective Conductor	Included in 3-core and higher versions	Not applicable in armour; earth connection handled differently
Magnetic Properties of Armour	Steel wire armour is ferromagnetic	Aluminium armour is non-magnetic, which is important for AC circuits
Usage Note	Suitable for use in AC circuits with multiple cores	Steel wire armour on single-core cables is not recommended for AC due to magnetic effects

Major Challenges of Cutting and Stripping SWA Cable

Cutting and stripping Steel Wire Armoured (SWA) Cable can be challenging. The tough steel armour requires specialised SWA Stripping Tools to avoid damaging the inner conductors, and the process can be both time-consuming and potentially hazardous. Improper handling may lead to injury or compromise the integrity of the cable. Removing the armour cleanly without deforming the cable, while also maintaining a reliable earth connection, is a critical but tricky step. Using the right techniques and purpose-built SWA Stripping Tools is essential to ensure both safety and efficiency on-site.

How to Install and Lay SWA Cable with Confidence

When installing armoured cable underground, it’s essential to bury it deep enough to prevent damage or disruption. If the ideal depth isn’t achievable, you should either increase the burial depth or provide additional protective measures to safeguard the cable.

While BS7671 does not set a fixed minimum depth, best practice recommends installing cables at least 450 mm below ground level to avoid common disturbances. In areas with a higher risk of interference, you should extend this burial depth to 600 mm.

For direct burial, surrounding the cable with sharp sand creates a protective layer that shields the sheath and insulation from damage. Placing an electrical warning tape above the sand also alerts anyone digging that a cable lies beneath. When running cables through conduit, always fully seal the pipe to keep out moisture.

Proper earthing of the SWA Cable is equally important, whether or not the armouring itself serves as the protective conductor. This is essential to comply with Automation Disconnection of Supply (ADS) Standards while preventing potentially hazardous faults.

Finally, electricians should always perform thorough testing after installation. Only qualified personnel should carry out comprehensive safety and compliance checks to ensure a secure and reliable connection.

Master SWA Cable Cutting and Stripping with the SACS Tool

The rising number of injuries among electricians handling SWA Cable, combined with tighter Health and Safety regulations, led most major contractors to ban blades and cable knives on-site. This created a clear need for a safer, more efficient stripping solution. Enter the SACS Tool (SWA Cable Stripper) instead! This welcome innovation addresses the issue while eliminating the drawbacks of previous cutting and stripping methods.

SACS Tool: A Quick 5-Step Guide

Invented by Martin Barrett, an electrician with 30 years’ experience, the SACS Tool makes stripping SWA Cable safe and easy. Just follow these 5 simple steps below:

	STEP 1 Position the tool on the cable at the gland point and advance the cutting wheel into the outer insulation. Rotate the tool around the cable to cut fully through the insulation, then continue advancing the cutting wheel into the steel strands to the required depth. Repeat the insulation-only cut approximately 2 inches further along the cable.
	STEP 2 Rotate the tool 90 degrees to the cable at the first cut point and advance the cutting wheel into the insulation. Guide the tool along the length of the cable, maintaining the correct cut depth, and adjust the cutting wheel as needed to ensure a clean cut through the insulation.
	STEP 3 Split and remove the outer insulation sheath. Unwind the steel strands and break them at the cut point using fingertip pressure. Then remove the remaining insulation and carefully splay the strands.
	STEP 4 Position the tool on the cable where the secondary insulation needs to be removed. Advance the cutting wheel and make a rotary cut to the required depth. Take care not to overcut, as this could damage the conductors.
	STEP 5 Rotate the tool 90 degrees to the cable and advance the cutting wheel into the insulation. Guide the tool along the length of the cable to achieve the correct cut depth. Then split the secondary insulation layer and remove it to expose the conductors.

Check Out the SACS Tool!

Frequently Asked Questions

Where are SWA Cables typically used?

They’re common in underground power, outdoor systems, industrial sites, and railways needing tough cable protection.

What are the main components of an SWA Cable?

SWA Cables consist of copper conductors, XLPE insulation, PVC bedding, armour (steel or aluminium), and a PVC sheath for protection and durability.

How do SWA and AWA Cables differ?

Multi-Core Cables use Steel Wire Armour (SWA), while Single-Core Cables use Aluminium Wire Armour (AWA) to minimise magnetic interference.

Can single-core cables use Steel Wire Armour?

No. Single-core cables should use Aluminium Wire Armour (AWA) to prevent magnetic interference in AC circuits.

Can electricians use the Steel Armour as the Earth Conductor?

In some cases, electricians use the Steel Armour as the Earth Conductor. However, you often need a separate earth core or wire to meet safety standards.

When should I use BS6724 LSZH SWA Cable?

Use BS6724 LSZH cables in public or enclosed areas to reduce smoke and toxic fumes in a fire. BS5467 is suitable for standard low-voltage applications.

What is the recommended burial depth for SWA Cables?

Best practice is to bury SWA Cables at least 450 mm underground. In high-risk areas, increase the depth or add extra protective measures.

Why is cutting and stripping SWA Cables challenging?

The tough steel armour makes SWA Cables harder to strip than regular cables, and specialised tools are needed to prevent damage and injury. Using a modern SWA Stripping Tool, such as the SACS Tool, makes the process both safer and more efficient.

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