commonly used, although waterproof PVC sheathed power cable, etc. is better than PE sheathed power cable, but the conditions in the fire, PVC releases harmful gases away than polyethylene. Almost all cable manufacturers are producing PVC sheathed power cable, of which only some manufacturers also produce PVC sheathed power cable.

retardant: flame retardant products than non-flame retardant products can provide 15 times more escape time; flame retardant material burned only non-flame retardant materials, l / 2; flame-retardant materials, heat release rate non-fire-retardant materials, l / 4; combustion products, the total amount of gas poison gas, such as the considerable amount of carbon monoxide, said only non-flame retardant products, the product l / 3; ordinary non-flame retardant products and products tobacco production performance, the amount of smoke is no big difference. Flame retardant cable according to GB12666.5-90 standards are divided into A, B, C three, in engineering design class should choose A flame retardant cable. Reduction in the same fire cut off (for example, the same bridge, the same shaft) the number of cables within the help to improve the flame-retardant cable capacity.

resistant cables: Under GBl2666.6 regulations, fire test the temperature is divided into two categories: A class examination 950-1000 ℃ for 90 minutes

B class assessment 750-800 ℃ for 90 minutes. The cable in the external fire source 750-800 ℃ (or 950-1000 ℃) direct combustion, the 90-plane can still power to determine the B-Class or A class fire cable.

refractory organic copper conductor cable in the fire surrounding the mica tape (high temperature 800 ℃) as a fire-resistant layer, and then squeezed into a certain thickness according to different models of the normal insulating layer, and finally filled cable core between the outer layer and the Like ordinary cable sheath. Inorganic insulation, also known as mineral insulated cables or magnesium oxide, its external sheath or special brass alloy for the tubes, the outer jacket and the copper conductors, magnesium oxide as the insulating material between the filling, due to the melting point of magnesium oxide 2800 ℃, brass (outer sheath) of the melting point is 1083 ℃, special alloy pipe can guarantee 825 ℃ without distortion, so long as the outer sheath is not damaged, the cable will be able to work, far more than the fire resistance of refractory organic cable. Do not the proposed project design requires the use of Class A fire-resistant cables, because the NH-YJV or NH-VV general requirements are lower than the A class, and although the fire resistance of mineral insulated cables excellent, but the cost is much higher than normal fire-resistant cable, more stringent requirements on the construction, the other as a single-core cable, the relative N, on the PE space, the single-phase short circuit, ground circuit impedance (electrical resistance) have some differences.