In order to transmit power reliably and safely to residences, companies, and industrial locations, underground cable installations are an essential part of today’s electrical infrastructure. The selection of conductor and protective wrapping is of utmost importance when burying electrical lines. Steel Wire Armoured (SWA) cable provides unparalleled mechanical protection, electrical performance, and longevity compared to other cable types, making it the clear choice for almost all subterranean applications. Subterranean electrical service installations should always use SWA cable, and this paper will explore the compelling reasons why.
Strong Underground Security is a Must
Electrical conductors face inherent challenges in the underground environment. There are several possible stresses that cables buried below ground may experience, such as mechanical damage from later excavation work, pressure from soil and underlying structures, and hazards posed by rocks, rats, or shifting earth. System failure, short circuits, and serious safety risks result from insulation and conductor integrity being quickly eroded in the absence of proper protection. In this regard, the SWA cable truly shines.
The galvanised steel strands that encase the inner core of SWA cable are its distinguishing characteristic. This armouring is like a fortress, protecting the wearer from crushing forces and impact harm with its imposing physical barrier. In the event that the cable is accidentally struck by a spade or during a drilling operation, the steel wires are engineered to absorb the impact, shielding the live conductors underneath. When it comes to subterranean deployment, the SWA cable stands out as the sole practical option thanks to its unmatched mechanical protection.
Protection from Earth Faults and Safety using SWA Cable
Subterranean applications require SWA cable’s built-in safety features in addition to its physical resistance. As per the UK wiring rules, the SWA cable’s armouring is expressly meant to be used as the earth, or Circuit Protective Conductor (CPC). A huge benefit is the fact that it serves as mechanical protection and an earthing path simultaneously.
The low resistance of the steel wires guarantees a strong short circuit and earth fault current channel in the event that the cable sustains damage and a phase conductor comes into touch with the steel armour. The supply-end protection device (such as a fuse or circuit breaker) is nearly immediately triggered by this rapid and high-current flow, isolating the problem and restoring system safety. The SWA cable is inherently safer than its unarmed counterparts because it relies on the armour as the earth path, which greatly improves the subterranean installation’s safety profile. This degree of safety should be given precedence in any underground installation, making the use of SWA cable an absolute must.
Resilience and Lifespan in Extreme Environments
The life and dependability of a power source are directly proportional to the strength of the electrical cable. A buried electrical wire should continue to provide power for decades or perhaps centuries without any further attention. This rigorous standard is precisely met by the SWA cable. A Polyvinyl Chloride (PVC) or Low Smoke Halogen Free (LSHF) outer sheath protects the internal components from moisture, chemicals, and ultraviolet light (UV), which is less of an issue below ground, but the sheath is still used during installation and storage.
Galvanisation prevents corrosion on the steel wire armouring that sits beneath this outer layer. No matter how wet or dirty the soil gets, the insulation and conductors will stay dry thanks to the three levels of protection: the outside sheath, the steel wires, and the interior bedding layer. Without the SWA cable’s superior mechanical and chemical durability, regular unprotected cables would burst sooner, causing greater damage and more disruption during excavation and repair. The only reasonable option for long-term performance and peace of mind is to specify SWA cable.
Compliance and Practical Considerations for Installation
The electrical contracting sector has long-established and simplified procedures for handling and installing SWA cable, which is a practical consideration. Termination and glanding techniques for SWA cable are standard practice for electricians. Specialised glands are used to secure the armouring, provide an earth connection and preserve the enclosure’s IP rating. You can always count on a safe, compliant, and electrically sound termination when you follow this standardised approach.
On top of that, using SWA cable for direct burial is frequently implied or stated as a requirement of UK wiring standards. Alternative approaches, such as encasing unprotected cables inside ducting, are theoretically feasible but come with extra complexity, expense, and the risk of mechanical protection being compromised by the ducting itself. The most basic, reliable, and economical way to meet the safety and mechanical protection standards for underground circuits is to bury the SWA cable directly. The installation process is made easier with the SWA cable due to its inherent protection and simplicity, which also ensures the highest safety standards.
Considering the Economy and the Environment
Although SWA cable may have a somewhat higher upfront cost compared to an identical unarmoured cable, the long-term economic benefits more than make up for this little difference. You can save a tonne of time and money if you can prevent even one cable issue from necessitating excavation, fault investigation, repair, and re-laying of ground surfaces. Over the course of the installation’s lifetime, the total cost of ownership is drastically lowered because to the SWA cable’s remarkable longevity and reduced failure risk.
A more sustainable infrastructure is the result of an installation employing SWA cable, which has a longer life and requires less maintenance. A decrease in the frequency of replacements reduces the demand for raw materials, the amount of trash produced by discarded cables, and the amount of energy needed for repairs and maintenance. After careful consideration, it is clear that SWA cable is the best option, both from an engineering standpoint and from a financial and ecological standpoint.
Finally: Your Only Option
To sum up, a fundamental tenet of good electrical engineering practice is the decision to use SWA cable for subterranean installations. Unlike other types of cables, this one has strong steel wire armouring that protects it mechanically against crushing and impact. The installation’s safety profile is greatly enhanced by the armor’s built-in capability to function as the Circuit Protective Conductor, which guarantees the safe and immediate isolation of earth faults. With its exceptional resistance to moisture and chemical intrusion, the SWA cable provides years of dependable performance without the need for maintenance. When it comes to commissioning an underground electrical circuit, the choice is crystal apparent for any electrician, engineer, or property owner: SWA cable is the way to go for the system’s lifespan, dependability, and safety.