Fire resistance characteristics NH-YJV fire-resistant cable

Fire resistant cables can maintain normal power supply for a period of time during a fire, while flame-retardant cables do not have this characteristic. This characteristic determines that fire-resistant cables play an important role in modern urban and industrial buildings, because once a fire occurs, the power supply circuits of control, monitoring, guidance, and alarm systems must maintain normal operation.

1Structural characteristics of fire-resistant cables
The structure of fire-resistant cables is basically the same as that of ordinary cables, with the difference being that the conductors of fire-resistant cables use copper conductors with good fire-resistant properties (copper has a melting point of1083Add a fire-resistant layer between the conductor and insulation layer at a temperature of ℃. The refractory layer is composed of multiple layers of mica tape wrapped around it. Due to the significant difference in the allowable working temperature of different mica tapes, the key to the fire resistance performance of cables is mica tapes.
2Classification of fire-resistant cables
Fire resistant cables are divided intoAClass andBClass:BCategory cables can be used in750℃～800At least withstand combustion in flames at ℃ and rated voltage90minAnd the cable is not punctured (i.e3AThe fuse does not melt. On the basis of improving the manufacturing process of refractory layers and increasing refractory layers, we have also developedAClass fire-resistant cable, it can be used in950℃～1000At least withstand combustion in flames at ℃ and rated voltage90minAnd the cable is not punctured (i.e3AThe fuse does not melt.AThe fire resistance performance of fire-resistant cables is superior to that of fire-resistant cablesBClass. Fire resistant cables can be used in important wooden public buildings, high-temperature locations, and other places with high fire resistance requirements and acceptable economic viability.
3Precautions for selecting fire-resistant cables
（1）When fire-resistant cables are used in cable tunnels with dense cables, cable interlayers, or in flammable places such as near oil pipes and oil depots, they should be selected firstAClass fire-resistant cable.

（2）Fire resistant cables are mostly used as power supply circuits for emergency power sources, requiring normal operation during a fire. Due to the rapid increase in ambient temperature during a fire, in order to ensure the transmission capacity of the power line, for circuits with long power supply lines and strictly limited allowable voltage drops, the cross-section of fire-resistant cables should be enlarged by at least one level.
（3）Fire resistant cables cannot be used as high-temperature resistant cables.
（4）To reduce the probability of cable joint failure in fire accidents, the number of joints should be minimized as much as possible during installation to ensure the normal operation of the line in a fire.