Types of Power Wiring System: Trunking, Ducting, catenary and Tough Sheathed Cable
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Types of Power Wiring System
Types of Power Wiring System- All those systems or methods of wiring which are used for the wiring of industrial and commercial centers are called power wiring systems. As industrial and commercial wiring is generally used for heavy loads, therefore any wiring based on heavy loads is called power wiring. In industrial and commercial centers, generally, the following wiring systems or methods are adopted. However, of all these power wiring systems, such a system should be selected according to one’s needs which are relatively safe, durable, cheap, and specifically according to the needs and nature of the environment or working conditions.
- Trunking Wiring System
- Ducting Wiring System
- Catenary Wiring System
- Tough Sheathed Cable System
Trunking Wiring System
A casing or sheath made of steel or some other insulating material (plastic), one side of which can be opened (so that cable can be inserted or ejected through it from there), is called a trunk. A trunking wiring system means such a modern wiring system, in which a very large number of small cables or multiple lengthy cables are spread inside steel sheets or plastic-made trunks, and these trunks are closed through covers or lids to complete the wiring. In this system, small and large cables can be used together, however, its dependency on the number of these cables is restricted through the wiring regulations. Normally, breadthwise trunks range from 2/3 inches x 2/3 inches to 9 inches x 4 inches (i.e., from 4 x 4 cm to 23 x 10 cm). However, trunks larger than this size can also be installed. Trunking is normally designed in 6 feet or 8 feet lengths, along which all necessary accessories e.g., bends, tees, flanges, reducers, etc., exist just similar to conduit wiring. Remember that if trunking is steel-made, it should be electrically continuous and inevitably be earthed. A Trunking system is commonly used in large industrial and commercial installations.
Ducting Wiring System
A duct means a passage or path for spreading one or more cables underground or on construction, which remains closed from above. Thus, an underground system of ducting, in which concrete ducts are constructed under the floor or inside the ground, for spreading cables, is known as ducting wiring system. In other words, a closed path an underground or in an under-construction building, which is used for passing one or more than one cable, is called ducting system. Apart from concrete, trunks can also be fabricated from iron, wood, fiber, etc. However, the usage of wood and fiber is less compared to concrete and iron.
Earth or floor is excavated in a round or rectangular shape for earthing. After this, concrete ducts are constructed in this digging, on which cables are placed. Then iron or concrete slabs are laid on them so that they could be removed as and when required. This type of wiring system is used in large buildings, government buildings, large stores, offices, airports, oil refineries, powerhouses, industrial and commercial organizations, etc.
Catenary wiring System
A wiring system in which cables are hung with steel wires which are firmly fastened through eye bolts and strainers along roofs or ceilings of high–rise buildings, is called a catenary system. In fact, this system has been designed for extremely tall buildings with high roofs or open areas where installation of steel conduit proves difficult and expensive.
The Catenary system of wiring consists of multiple specific structured VRI cables. In the middle of every VRI cable, highly tensile strength galvanized steel wires exist, which can sustain extreme strain or tension. Jute or hemp is being filled between this VRI cable and steel wires so that the cables’ roundedness does not get affected. Then a braided protective casing or sheath is placed above this entire cable, after which no further safety measures for this cable are required. However, if considered necessary, another metal cover or casing can be placed above it for confronting special or extreme conditions.
As this cable can tolerate extreme stress or strain, therefore it is firmly tied along the roof of some high–rising building at any two points, or the cable is hung with the help of a beam fitted in the building. As such, cable is spread from one point to another by means of hanging it between two points through a catenary wire. (The curve or waft which is formed as a result of the freely hanging of wires between two points, is called catenary). Remember that eye bolts are being applied for tying up the cables.
Catenary wiring is mostly used for overhead bus bar systems and street lighting. This system of wiring remains protected against moisture and water. Further, the wiring weight on the building is also less. Catenary wiring is relatively less costly and its repairing costs are also low. Remember that all metal catenary wires must inexorably be earthed.
Tough Sheathed Cable System
A system of wiring, in which an extra tough protective sheath exists on a cable apart from its own insulation, which safeguards the cable against mechanical and external effects, is called a tough sheathed cable system. Tough rubber, PVC, plastic, and lead are used as the tough sheath. Thus, tough rubber (T.R.S) cable, PVC sheathed cable, plastic-sheathed cable, and lead alloy sheathed cable are commonly used in different sheathed cable systems. Wiring is done by placing these cables on a conduit or directly on walls through buckle clips or installing them on a batten. In this type of wiring, mostly tough rubber sheathed (T.R.S) or cab tire sheathed (C.T.S) or lead sheathed is used. Tough rubber sheathed cables consist of vulcanized rubber insulated conductors, on which an extra tough rubber protective sheath is put apart from the cable’s insulation. Whereas, instead of tough rubber, a lead sheath is cast on a lead sheathed cable, the benefit of which is that it can also simultaneously be used as earth besides protection. However, whitewash or cement, etc., may damage this cable. As rubber sheaths cannot withstand or confront certain specific conditions (e.g., oil, acid, hot sunlight), therefore wiring with such sheaths should be used in those places, where no dangers of its damage exist. The tough sheathed cable being applied in this system is commonly available as single-core, two-core, three-core, and two-core with earth conductors.
Sheathed cables can directly be buried under the plaster on walls or roof surfaces, underneath wooden floors, or inside the walls and roofs. Moreover, this type of cable can be installed in all those places, where conduit has not been used. As compared to conduit, a tough sheathed cable system is quite economical and cheap, remains protected against mechanical concussions, and can be installed easily and forthwith. Further, additions and alterations are also possible within it later on. However, a disadvantage of this type of system is that as a result of surface wiring, charm or attractiveness diminishes. This system of wiring is quite an ancient one, however, it is still being used at specific places in commercial and industrial centers (e.g., alongside fire furnaces walls in factories, where wiring is done directly by means of fixing tough sheathed cable thorough buckle clips)
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