In recent years, the proportion of power system interruptions caused by power cable fires has been increasing worldwide. Therefore, in power plants, substations, and other locations with large electrical equipment and densely laid cables, the use of flame-retardant cables to prevent the spread of fire and fire-resistant cables to ensure uninterrupted power supply to critical circuits has become increasingly important. Let's take a look at what fire-resistant cables are and what grades they fall into.
What is fire-resistant cable?
1. Fire-resistant cable - Cables that can maintain safe operation for a certain period of time under flames are fire-resistant cables.
2. Implementation standard:
GB/T19666-2005
3. Applications of fire-resistant cables:
Fire-resistant cables are widely used in high-rise buildings, subways, underground shopping malls, large power stations, and key industrial and mining enterprises, where fire safety and firefighting are crucial.
What grades are fire-resistant cables?
Fire-resistant cables are classified into four grades:
Grade 1: NH-IA
NH-IB
Grade 2: NH-IIA
NH-IIB
Grade 3: NH-IIIA
NH-IIIB
Grade 4: NH-IVA
NH-IVB
Note: Grade A indicates a fire test flame temperature of 950-1000°C and a continuous fire duration of 90 minutes.
Grade B indicates a fire test flame temperature of 750-800°C and a continuous fire duration of 90 minutes.
From the above introduction to fire-resistant cables, we can also see that the structure of fire-resistant cables is basically the same as that of ordinary cables. The difference is that the conductor of fire-resistant cables uses copper with high fire resistance (copper has a melting point of 1083°C) and a fire-resistant layer is added between the conductor and the insulation. The fire-resistant layer is made of multiple layers of mica tape. Because the allowable operating temperatures of different mica tapes vary significantly, the mica tape is the key to the cable's fire resistance.
