This article explains the principles and types of fire-resistant cables for industry professionals.
Fire-resistant Cables
1. Cables primarily have copper conductors:
Conductors can be categorized as bare copper, copper-plated copper, copper-clad steel, copper alloy, and copper foil.
Bare copper—low conductor resistance, easily oxidized. Copper plating—enhanced oxidation resistance.
Tin-plated copper—enhanced oxidation resistance, facilitating subsequent soldering. Silver-plated copper—high conductivity, high price, often used in radio frequency cables and fluoroplastic high-temperature wire.
Copper-clad steel—high strength, commonly used in overhead cables.
Copper alloy—high strength (copper with a small amount of other metal added).
Copper foil—high bending resistance and high flexibility (copper is pressed into thin sheets and wrapped around elastic fiber).
To increase conductor strength, multiple copper wires are often twisted together.
II. Cable Insulation:
Common insulation materials include PVC (Polyvinyl Chloride), SR-PVC (Semi-rigid PVC), PP (Polypropylene), PE (Polyethylene), Foam-PE, Foam-PE+Skin, and the latest magnesium oxide (MI) mineral insulator.
Types of Fire-Resistant Cables:
YTTW - Fire-resistant cable has a longitudinally welded copper tape outer sheath, while the inner cable core is insulated with fire-resistant mica tape. The final cable is finished with glass fiber or other fire-resistant fillers.
BBTRZ - Fire-resistant cable has the same structure as above, except the fire-resistant mica tape is replaced with ceramic silicone rubber tape. I'm not sure which of these two cables with different insulation is better.
NG-A - Fire-resistant cable has an aluminum outer sheath, replacing the longitudinally welded copper tape with a corrugated aluminum tape. The inner cable core may be wrapped with several layers of fire-resistant insulation tape.
BTLY - Fire-resistant cable has a continuous extruded aluminum tube outer sheath, and the inner cable core is also protected by a continuous extruded aluminum tube. Both the inner and outer aluminum tubes are bare and uncorrugated. This type of cable definitely has lower bending performance than flexible fire-resistant cables with longitudinally welded and corrugated tubes.
BTTZ - mineral insulated cable, also known as magnesium oxide cable. This type of cable should have better fire resistance, but the production process is very complicated, mainly because the filling of magnesium oxide powder is difficult. The equipment for producing this type of cable cannot be domestically produced, and it mainly relies on the introduction of advanced technology and equipment.
