Specifically, in confined underground public areas like road and rail tunnels, underground shopping centres, car parks, etc., fire temperatures can exhibit a very fast rise time and reach temperatures well above those in above ground buildings. Cables for electric Panels : These types of cables are suitable for domestic purpose, for installation in public area and for any internal wiring, switch boxes. Underground electrical cables can be particularly hazardous because they often look like pipes and it is impossible to tell if they are live just by looking at them. Halogens like Chlorine are particularly good additives that help retard flame propagation and don’t significantly impact the dielectric properties of the polymer, so Halogens are used in both cable insulations and in cable sheaths. Commonly used sheaths are made from polyvinyl chloride (PVC). A common material like polyvinyl chloride (PVC) is used for the sheath. Most common flexible cables are made from hydrocarbon-based polymers.

Certainly this is not because Americans are not wisely informed of the dangers, rather the approach taken is that: "It is better to have highly flame retardant cables which do not propagate fire than minimally flame retardant cables which may spread or contribute to a fire" (a small fire with some halogens may be better than a large fire without halogens). For this reason common British, IEC and Austrlian (AS/NZS61034) smoke tests conducted by burning cable samples in large 3 meter³ chambers with plenty of air may provide misleading smoke figures because complete burning in flame can release less smoke than partial incomplete burning or smoldering which is likely in practice (in America NFPA 130 calls for smoke tests in both flaming and non-flaming modes). Often standard PVC cables may also release large amounts of acrid smoke. Grey coloured sheath now almost exclusively used on PVC cables. In America, many building standards do not require halogen free cables. Certainly this volume of heat will accelerate the burning of other adjacent materials and may help spread the fire in a building but importantly, in order to generate the heat energy, oxygen needs to be consumed. The Heat Release Rate and volatility in the air for these materials will differ but the fuel added to a fire per kg and the consequential volume of heat generated and oxygen consumed is relative.

Burning Polyethylene (which can be seen from the table above has the highest MJ fuel load per Kg of all insulations) will generate almost 3 times more heat than an equivalent PVC cable. Research by Universities, Institutions, and Authorities in Australia and around the world have identified that for modern above ground cellulosic buildings, the use of light weight thermoplastic building materials, synthetic foams, and fabrics, along with synthetic materials and plastic contents have significantly increased dire loads resulting in time temperature fire profiles well above the original parameters of the existing, early 1900’s test protocol ISO834-1 (AS/NZS1530pt4) as mandated by the Australian NCC. Enclosing cables in steel conduit will reduce flame propagation at the point of fire but hydrocarbon based combustion gasses and smoke from the decomposing polymers will propagate along the inside of conduits to switchboards, distribution boards and junction boxes in other parts of the building where any spark such as the opening or closing of circuit breakers, or contactors is likely to ignite the combustible gasses leading to ignition or even explosion and spreading of the fire and smoke to other locations. This consists of solid copper or steel conductor plated with copper which is enclosed in the metallic braid and metallic tape.

In other words, every wire is a cable, but not every cable is a wire.Most of the time, anything that isn’t a single conductor with or without insulation is referred to as a cable. In Australia, unlike any other country, AS/NZS3008.1.1:2017 has tables allowing some cable designs to operate at conductor temperatures to 110°C. Whilst technically possible for the cables, what has not been fully considered by Australian standards is the intrinsic change this cable operating temperature may have on the cable’s flammability. Where cables are required to be flame retardant to Australian Standard test methods AS/NZS60332-3 it is concerning these tests are not conducted on cable samples preconditioned to the operating temperature, rather commencing at room temperature. To provide cables which are halogen free, cable makers most often choose polymers like polyethylene (PE & XLPE) because it is easy to process and cheap however, although polyethylene is halogen free it has a naturally high fire load. Halogen-Free Flame Retardant cables often use a more pure polymer like Polyethylene (PE or XLPE) or EPR for the insulation which has good electric and mechanical properties but may not be very flame retardant.

If you have any sort of inquiries relating to where and just how to use what are electric cables, you could call us at our own web page.