Steel Wire Armoured Cable

What is Steel Wire Armoured Cable?

Steel Wire Armoured Cable, also known as SWA cable, is a type of electrical cable commonly used in power distribution networks. It is designed to provide robust protection to the inner cabling, allowing it to be used safely in various environments and applications.

Definition of Steel Wire Armoured Cable

Steel Wire Armoured Cable consists of a set of electrical conductors, typically made of copper or aluminum, which are insulated and then protected by a layer of steel wire armor. The armor is designed to provide mechanical protection to the cable, while also offering some level of resistance to moisture, corrosive liquids, and other environmental hazards.

Components of Steel Wire Armoured Cable

The main components of an SWA cable include the electrical conductors, the insulation material used to insulate them, and the steel wire armoring used to protect the assembly. The wires are typically twisted together to form a tight bundle, which is then wrapped in multiple layers of insulation material. The steel wire armoring is then applied, providing a tough outer layer that helps to protect the cable against various hazards.

Advantages of Steel Wire Armoured Cable

One of the main advantages of an SWA cable is its ruggedness and durability. It is able to withstand a range of environmental conditions, including exposure to moisture, dust, dirt, and extreme temperatures. Moreover, because it is armored, it can withstand damage from impacts and compression. Another benefit of SWA cable is its ease of installation, as it can be run in much the same way as other electrical cables.

Disadvantages of Steel Wire Armoured Cable

On the downside, SWA cable tends to be more expensive than other types of electrical cabling due to the additional materials and manufacturing processes involved. This can make it a less cost-effective solution for some applications. Additionally, the armored construction can also make it more difficult to bend and shape the cable in certain configurations, which may limit its use in some situations.

Applications of Steel Wire Armoured Cable

SWA cables find use in a variety of applications, including outdoor power distribution systems, where they are routinely buried or exposed to harsh weather conditions. They are also used in hazardous or corrosive environments, such as chemical plants, oil refineries, and mines, where the cable needs to be protected against exposure to corrosive materials. Additionally, SWA cables are often used in heavy industry and infrastructure projects, where they can provide reliable and long-lasting performance.

How is Steel Wire Armoured Cable Constructed?

Overview of Steel Wire Armoured Cable Construction

SWA consists of four main components – steel wire armour, copper or aluminum conductor, insulation materials, and PVC sheath. The cable’s construction process involves the assembly of these components into a robust, flexible, and durable cable that can withstand harsh environmental conditions. The steel wire armour provides mechanical protection, while the insulation materials and PVC sheath provide electrical insulation and protection against various external factors such as moisture, UV radiation, and temperature variations. The copper or aluminum conductors are responsible for conducting the electrical power, making SWA an essential component in power distribution systems.

Steel Wire Armour

The steel wire armour is a critical component of SWA, providing robust mechanical protection to the cable. It consists of a steel wire helix that is wrapped around the cable’s core, forming a protective layer. The steel wire helix is made up of galvanized or tinned steel wires, which provide superior protection against physical damage, including crushing, impact, and abrasion. The thickness of the steel wire armour varies depending on the cable’s application, with thicker armor used where more severe mechanical protection is required.

Copper or Aluminum Conductor

The copper or aluminum conductor is a critical component that carries the electrical power through the cable. The choice between copper or aluminum depends on several factors, including the cable’s application, budget, and environmental conditions. Copper conductors are preferred because they offer lower resistance, higher conductivity, and better heat dissipation. However, aluminum is a more cost-effective alternative that can be used in situations where conductivity is not critical, and budget is a concern.

Insulation Materials

Insulation materials are used to prevent electrical current from leaking out of the cable and coming into contact with people or objects. The insulation material used varies depending on the cable’s application and the required electrical parameters. SWA cables often use cross-linked polyethylene (XLPE) or ethylene-propylene rubber (EPR) for insulation. These materials offer excellent electrical insulation properties and can withstand extreme temperatures, making them suitable for use in harsh environments.

PVC Sheath

The PVC sheath is the outermost layer of the SWA cable, providing additional protection against mechanical stress and environmental factors such as sunlight, water, and chemical exposure. PVC is a highly flexible material that conforms to the shape of the cable, making it easy to install. Additionally, PVC provides excellent resistance to chemicals, abrasion, and moisture, making it the go-to choice for outdoor applications.

What are the Core Configurations of Steel Wire Armoured Cable?

Single Core Steel Wire Armoured Cable

Single core steel wire armoured cable consists of a single conductor that is surrounded by insulation, steel wire armour, and a sheath. This type of cable has only one phase and is used for power transmission over long distances. Single core steel wire armoured cable is also suitable for underground installations where moisture or physical damage could be a concern.

Multi-Core Steel Wire Armoured Cable

Multi-core steel wire armoured cable is a type of cable that contains more than one conductor. Each conductor is surrounded by insulation, and all the conductors are encased in a single sheath. The cable may have two, three, or four cores and is used for power distribution in commercial and residential buildings. Multi-core steel wire armoured cable can carry multiple phases of electricity, making it an ideal choice for a broad range of applications.

Dual Steel Wire Armoured Cable

Dual steel wire armoured cable is a type of cable that consists of two single-core cables, each one covered with steel wire, in a single sheath. This type of cable provides additional protection against physical damage and is suitable for underground installations where moisture or extreme temperatures can be an issue. Dual steel wire armoured cables are commonly used in industrial applications requiring high reliability.

Three-Core Steel Wire Armoured Cable

Three-core steel wire armoured cable consists of three conductors, each surrounded by insulation, steel wire armour, and a sheath. This type of cable is used for power distribution in three-phase systems and is suitable for use in residential, commercial, and industrial applications. Three-core steel wire armoured cable is designed to withstand harsh weather conditions and mechanical stress.

Four-Core Steel Wire Armoured Cable

Four-core steel wire armoured cable is a type of cable that contains four conductors. Each conductor is surrounded by insulation, and all the conductors are encased in a single sheath, which also contains steel wire armour. This type of cable is used for power transmission and distribution in high-voltage systems. Four-core steel wire armoured cable has high levels of durability and is capable of carrying immense amounts of power.

How is Steel Wire Armoured Cable Used in Electrical Installations?

Installation Methods of Steel Wire Armoured Cable

Two primary methods of installing Steel Wire Armoured Cable are direct burial and cable ducting. Direct burial involves laying the cable directly into the ground without adding any additional protection. This method is ideal for installations that do not require significant cable depth or where there are not many external factors that could damage the cable. On the other hand, Cable ducting is an alternative approach that involves laying the SWA cable inside a protective conduit. This method provides additional protection against environmental damage such as soil erosion and offers flexibility when adding cables in future.

Direct Burial of Steel Wire Armoured Cable

To bury an SWA cable directly, it is essential to ensure that the ground is excavated to a suitable depth. The minimum cable depth varies by country and installation type. However, it is essential to ensure that the cable is planted deep enough to protect against accidental cuts during excavation or environmental damage. Direct burial installation requires proper cable routing, individual conductors exposed to 5mm without damaging the insulation, and adequate connections between the conductors.

Use of Steel Wire Armoured Cable in Cable Ducting

Cable ducting is an excellent installation method for SWA cables that require an extra layer of protection. The ducting approach entails laying the SWA cable inside a conduit with an additional layer of protection. Before starting, it is crucial to clear all obstructions from the site, such as stones or roots, as they could damage the conduit during installation. Cable ducting is slightly more expensive than direct burial of SWA cables, but it is increasingly preferred due to its added layer of protection and its easy to maintain.

Electrical Cable Calculator for Steel Wire Armoured Cable

The electrical cable calculator for Steel Wire Armoured Cables is a tool that allows electrical engineers to determine the size and calculated weight of SWA cables. The tool is essential for ensuring the cable sizes are appropriately matched for the required power load. The calculators are readily available online and allow engineers to calculate the size and weight of SWA cables for any length or power capacity per meter for their electrical installation projects.

Dealing with Steel Wire Armoured Cable in Power Networks

Safety should be a top priority while dealing with Steel Wire Armoured Cables in power networks. Electrical engineers should follow the safety guidelines recommended by their countries as well as the manufacturer of the SWA cables being installed. In case of cable damage or overloading, the engineer should power off the affected areas, wear protective gear, and promptly address the issue.  It is also essential to adhere to local regulations for disposing of old and unused cable to prevent environmental degradation.

What are the Specifications and Standards for Steel Wire Armoured Cable?

BS 6724: Specification for Steel Wire Armoured Cable

BS 6724 is a British standard that specifies SWA cables for power distribution in low voltage applications between 600/1000V to 19000/33000V. It outlines the different types of SWA cable constructions, such as multicore and single-core, and their electrical and mechanical requirements. This standard also covers the cable’s insulation, sheathing, and armouring materials, including their fire performance, resistance to water penetration, and temperature rating.

Steel Wire Armoured Cable for Low Voltage Applications

SWA cables for low voltage applications typically use XLPE (cross-linked polyethylene) insulation and PVC (polyvinyl chloride) or LSZH (low smoke zero halogen) sheathing. These cables are ideal for internal and external use in fixed installations, such as buildings, industrial plants, and power stations. They offer excellent resistance to electrical interference, abrasion, and water penetration while complying with the BS 6724 standard.

Steel Wire Armoured Cable for High Voltage Applications

SWA cables for high voltage applications require different materials and designs to meet the stringent safety and performance requirements of transmission and distribution networks. These cables can operate at voltages between 33kV to 400kV, and they use ethylene propylene rubber (EPR) or paper insulation and PE (polyethylene) or PVC sheathing. They feature thicker conductors, higher copper content, and advanced armouring for mechanical protection and resistance to environmental stress.

Steel Wire Armoured Cable with LSZH Sheath

Steel wire armoured cables with LSZH (low smoke zero halogen) sheathing are environmentally friendly and offer better fire resistance than PVC sheathed cables. LSZH cables emit low levels of smoke and toxic gases, making them ideal for indoor installations where people are present, such as public buildings, hospitals, and schools. They also meet the international standard IEC 60332-3 for fire performance.

Steel Wire Armoured Cable for Direct Burial

SWA cables for direct burial have a robust and durable construction that allows them to endure harsh underground environments. They feature heavy-duty steel wire armouring and polyethylene or PVC sheathing for high mechanical protection and durability. They are ideal for outdoor installations such as power distribution lines, street lighting, and oil and gas pipelines.

What are the Advantages of Steel Wire Armoured Cable?

Mechanical Protection Provided by Steel Wire Armour

One of the primary advantages of using steel wire armoured cables is the mechanical protection provided by the steel wire armor. The armor is designed to protect the cables from stress and external damage, such as impact, twisting, bending, and compression. It also ensures that the cables can withstand harsh environmental conditions, including moisture, chemicals, and UV radiation. The armor is made from galvanized steel wires, which are tightly wound around the cable, providing a robust and durable shield against external elements. The mechanical protection provided by steel wire armor makes these cables ideal for use in applications that require high levels of mechanical strength and durability, such as outdoor lighting and power distribution.

Resistance to Stress and External Damage

The high stress resistance and durability of steel wire armoured cables make them an excellent choice for projects that require long-lasting performance. These cables can handle high levels of stress, making them suitable for use in underground applications, where they may be subjected to high levels of pressure. Additionally, the armor provides protection against cuts, abrasions, and impacts, preventing damage to the cables and preserving their performance over time. The resistance to stress and external damage gives steel wire armoured cables a long lifespan, reducing the need for frequent maintenance and replacements.

Enhanced Fire Performance with LSZH Sheath

Another significant advantage of steel wire armoured cables is the enhanced fire performance provided by the low smoke zero halogen (LSZH) sheath. LSZH cables are designed with materials that emit low levels of smoke and do not release harmful halogens in the event of a fire. This reduces the risk of toxic smoke inhalation and fire spread, preserving the integrity of the cables and minimizing potential damage. The LSZH sheath also conforms to industry standards, including IEC and BS EN, making them suitable for use in buildings where fire safety regulations must be met.

Long Lifespan and Durability

Steel wire armoured cables have a long lifespan due to their robust construction and resistance to external damage. The armor protects the cables, preventing damage and preserving performance over time. Additionally, the cables are built with materials that can withstand harsh environmental conditions, including moisture, chemicals, and UV radiation. This ensures that the cables maintain their performance properties, reducing the need for replacement and maintenance. The long lifespan and durability of steel wire armoured cables make them a reliable and cost-effective solution for various projects.

Protection against Electromagnetic Interference

Steel wire armoured cables provide protection against electromagnetic interference (EMI), preventing the cables from being affected by surrounding electrical equipment. EMI can cause electrical interference, and potentially compromise the signals carried by the cables, leading to data loss and performance issues. The armor provides a physical barrier to shield the cables from EMI, ensuring reliable signal transmission. This makes steel wire armoured cables ideal for use in applications with high levels of EMI, such as power transmission and industrial automation.