Everything you need to know about outdoor power cable
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Installing cable outside? Discover which outdoor power cables are suitable for external use in our latest blog.
As the world adapts to a new normal, those working from home are increasing their use of their electrical facilities. Because of this, it may be necessary to set up remote buildings to use as workshops or home offices. This would require electrical professionals to assess the requirements needed to power the outbuilding, new building or separate building, such as, what is the load, what installation method is best, and how to plan the cable route.
For this to happen, outdoor electrical cable will need to be installed in order to power the building’s electrical services. So, what outdoor power cable should be used?
Cables designed for external use should be able to withstand the adverse conditions of the outdoors. The outer layer of the cable needs to be durable enough to protect the cable from mechanical damage, water, extreme variations of temperature, insect and rodent attacks, as well as UV exposure from sunlight. The electrical cable should also be protected during handling and installation. Cables for external use are heavy and unsuitable cable is likely to get damaged if they are mishandled or dragged around.
What is Steel Wire Armoured cable?
Steel Wire Armoured (SWA) cable is a power and auxiliary control cable, specially designed for use in mains supply electricity. It is used to distribute power in numerous outdoor and indoor applications such as underground systems, direct burial, cable networks, power networks, clipped direct and cable ducting. The steel wires are also galvanised to prevent failure due to rusting.
SWA Cable is sometimes referred to as Booklet Armoured Cable or more commonly as Mains or Power Cable.
These cables are often used for external applications because it features mechanical protection. Its armour is used to reduce the risk of damage to the cable while being installed and also by third parties after installation. SWA cables are rigid and heavy, which makes them very difficult to bend but also very robust and only increases their suitability for use underground or fixed to outdoor walls using cable cleats.
Depending on the application or purpose, the number of cores within the SWA cable can vary. Usually, SWA cables are constructed with class 2 stranded plain annealed copper wire conductors to comply with BS EN 60228. These are covered by an extruded layer of cross-linked polyethylene insulation. The insulated conductors are then ‘laid-up’ or helically wrapped together and a bedding layer extruded on top.
The electrical cable is then enclosed in a layer of armour to provide mechanical protection and completed with a PVC outer sheath which provides additional protection from daylight UV rays and water. For protection against artificial UV sources such as science projects, an additional barrier is needed. It is important to note that UV protection is an additional feature in SWA cables and is not a requirement in the BS 5467, BS 6724 or BS 7846.
SWA cables are commonly buried in the ground. Although the minimum depth is not stated in BS 7671, it is generally acknowledged that it should be buried at 600mm. SWA cables need to be buried at a sufficient depth to prevent disturbance in the ground.
What is the difference between SWA and AWA cables?
Steel wire armour is only used on multi core cables. So, when we talk about multi core SWA cable, we mean a cable with two or more cores.
Aluminium wire armour is used instead of steel when a cable has only one core because aluminium is non-magnetic. A magnetic field is produced when an alternating electric current passes through a cable. The higher the current, the bigger the electric field, and this field will induce an alternating electric current in nearby metallic elements such as the steel wire, which could cause overheating and significantly affect the current carrying capacity of the cable.
Prysmian SWA cables
What makes Prysmian SWA cables stand out? Our XLPE insulated, PVC sheathed SWA and AWA cables are manufactured in accordance with BS 5467.
Prysmian BS 5467 is a low voltage armoured power cable with XLPE insulation and mechanical protection provided by galvanised steel wire armour. The range comprises 1, 2, 3, 4, 5, 7,12, 19, 27, and 37 cores and is well suited to areas at risk of mechanical damage. BS 5467 3 core cables can be installed for outdoor applications and laid into cable ducts or underground cable trenches using the right cable pulling and laying equipment.
It can also be used indoors using cable cleats or appropriate cable ties in a variety of installations including LV industrial wiring, mains distribution and auxiliary control.
BS 5467 is currently the most calculated cable in our cable calculator tool CableApp where electrical professionals can select the best type of cables that are required for each type of project and installation, including outdoor cables. Learn more about CableApp here.
Prysmian LSOH armoured Cable is manufactured to BS 6724. The BS 6724 range can be used as a direct replacement for PVC sheathed standard BS 5467 armoured cables for applications where low smoke, zero halogen performance and reduced flame propagation is required.
Single core armoured cables require AWA, but since aluminium melts at 660 °C, and fire resistance tests are two hours at a temperature over 800°C, they are unsuitable for life safety systems and fire fighting systems. FP600s is not available as AWA for this reason so alternative methods are needed.
FP600s is our ultimate fire resistant, armoured cable for power and control of life safety and fire fighting systems used in buildings, available in two, three, four and five-core versions. The cable features conductors wrapped in mica-glass fire resistant tape in addition to XLPE insulation to maintain circuit integrity and operation during a fire. Discover more about FP600s here.
Power Cables that Deliver
The electrical industry has counted on us for over a century to deliver products that perform. Our heritage and dedication give you the tools and assurance to get the job done. We are Prysmian – the leaders who assure the stability, safety and supply of our industry.