What are Armoured Cables? What are they used for?
In the field of electrical power distribution, armoured cables are referred to as steel wire armoured cable (SWA). It is a power cable of hard-wearing which is designed for the supply of mains electricity. Aluminium is used for the purpose of Armouring, previously iron was used for this purpose. It is also used and applied to submarine communications cable. SWA (Steel Wire Armoured ) cable is basically used only on multicore versions of the cable. The multicore cable is the one where a number of different cores are present. In case, if the cable has only one core, AWA (Aluminium Wire Armour) is used in place of steel wire. There is the production of magnetic fields too by the current-carrying single
core cable resulting in induction of electric current in the steel wire which can then lead to overheating.
It also includes medium voltage and low voltage SWA steel wire armour 3 core cable and all of the sizes of the mentioned categories are used armoured cables have a current rating up to 33KV. As mentioned, in the case of single-core cables, AWA is used for preventing the induced current present in the armour.
Armoured power cables are available for both copper and aluminium conductors as per the requirement. In addition to this, Armour cables also provide additional protection where mechanical stress can cause potential damage to the cable, such as outdoors, underground or direct burial. Armour also enables the cable to withstand situations such as higher pulling loads. But yes, it must be noted that armour provides no protection towards unfavourable conditions. Armoured cables are also known as SWA cable, steel wire armoured cables, mains power cable, single-core power cable and multicore booklet armoured cable.
There are various advantages of which come along the Armoured cables:
- Temperature Resistance:
Steel has a melting point of about 15000C which is very high in comparison to aluminium and copper. For these, the melting point is about 6000C and 10000C respectively. This simply shows that for protection steel goes a long way out. It is able to protect the electrical current-carrying conductors against very high temperatures. Therefore, the durability of the transmissions via cable components are armoured with steel. It actually makes armoured cables a good solution for industries. These cables are manufactured as they are exposed to and are able to withstand variant temperatures.
- Advanced Mechanical Properties of Armoured Power Cable:
Cables that are of use in large industrial applications have a lot of challenges and issues at the time of transmission. Both the cables electrical and network are used for over long distances which directly exposes them to a lot of mechanical threats. These cables are placed overhead or underground as per the requirement. But whatever the case is these are exposed to direct mechanical damage.
Armoured cables are capable of protecting the inner components of the cable being used. Actual transmission can also be used from getting damaged by several external factors and thus hindering the transmission. It provides a surety that both power and network are available for the desired applications and thereby also making armoured cables a reliable way of transmission.
We now have cables that are particularly used for the mains grid, it is important that interference from the fellow cables are in the path of the transmission line. Only because of the amount of high power which is transmitted, use of armoured cables helps in providing insulation of transmission components from emitting the interference. It also protects from being affected by interferences caused by neighbouring cables and also appliances.
Armoured cables are better to be used in fixing conduit pipes as they are able to support by transporting large volumes of water over large distances.
Wiring done at places that pose a great danger to cables is a matter of concern and also their components such as locations with extreme weather conditions are likely to cause interference to the cables presently used.
What is an SWA? What are its uses?
It is an auxiliary control and power cable which is mainly designed for use in the mains supply. SWA (Steel Wire Armoured ) cables are designed in order to give mechanical protection and this is the reason that cable is used for external purposes since Armour reduces the risk of any physical damage including being pinched or damaged; steel is generally used for protection of Armoured cable. Since cables are heavy with respect to the weight which makes them very difficult to bend, these are suitable for use outdoors.
Construction of SWA Cables:
Construction of SWA can be broken:
- Conductor: Plain Stranded Copper (Cu) Conductor of Class 2
- Insulation: XLPE (Cross-Linked Polyethylene) is used as insulation.
- Bedding: PVC (Polyvinyl Chloride) is used for protection.
- Armouring: SWA
- Sheath: PVC
Using SWA for Earthing
Armour cable is used for grounding and is also subject to controversy in the electrical installation industry. This functionality is referred to as CPC (Circuit Protective Conductor). In usual, an additional core within the cable is categorized as the CPC. For instance: If a 3 core cable is used in place of 2 core cable for neutral and line and CPC which also runs along with the cable which serves as CPC.
The two major concerns are:
- Relative conductivity of armoured cable as compared to the cores (which decreases with increasing size of cable)
- Reliability and Safety and Health issues.
There were many pieces of research which took place and the results came that in most of the cases armouring cable must be used to serve as CPC under regulations.
Ease of SWA Cable while Cutting & Stripping:
As per the analysis, there was an increased number of electricians getting injured while working with SWA cable and that too with updated safety and health regulations which forced many contractors to ban blades and knives for use. It led to the development of a new SWA stripping tool as an urgency.