All kinds of special cable mine cable and rubber sheath cable selection

In many large or important buildings, in addition to normal power supply and distribution, but also equipped with diesel generators as emergency power. Once the grid power supply line special cable, mining cable, rubber cable problems or fire inside the building to make the mains trip power supply, it needs diesel generator set for temporary power supply, to ensure that the important work will not stop working, or ensure that the evacuation lighting instructions evacuation direction. The electricity generated by the diesel generator needs to pass through part of the low-voltage switchboard in the substation, and then feed through the low-voltage switchboard to the electrical equipment in need of emergency power. The diesel generator and the low-voltage switchboard of the substation are integrated power supply systems connected by fire-resistant cables or fire-resistant closed busbars.

Because fire-resistant rubber sleeve cable or fire-resistant closed busbar in addition to the power grid or line problems as an emergency power line, but also in the case of fire or other disasters as a transmission line. Therefore, fire-resistant cable or fire-resistant closed bus must be able to ensure normal transmission at high temperature. When the ambient temperature is higher than 700 ° C, the power supply can run for more than 1.5 hours, and the increase of the ambient temperature will not cause the decrease of internal insulation and lead to short circuit between wires. Under what circumstances should fire-resistant cables be selected, and under what circumstances should fire-resistant closed busbars be selected for China wire and cable network?

This is mainly determined by the capacity required from the diesel generator set to the low-voltage distribution cabinet and the space of the line direction. 1. Refractory rubber sheathed cables refer to the GB12706-91 standard, and their refractory characteristics should meet the requirements of GB12666.6-90. In cable models, refractory cables are NH as prefix, with armor (NH-YJV32) and without armor (NH-YJV). Armored special cable is slightly more expensive than unarmored cable. Because their structure is different. The structure of armored mine cable is divided into six layers, the middle layer is copper conductive wire core, the second layer of copper core is mica tape wrapped refractory layer, the third layer is crosslinked polyethylene insulation layer, the fourth layer is the lining layer, the fifth layer is steel wire armored (including six copper wires), the sixth layer is PVC sheath.

The structure of rubber sheathed cable without armor is divided into four layers, the first layer is copper conductive wire core, the second layer of copper core is mica tape wrapped refractory layer, the third layer is crosslinked polyethylene insulation layer, the fourth layer is PVC sheath.

At the same time, mining cables are divided into A and B fire resistance grades. The fire resistance temperature of class A is 950 ~ 1000℃, and the fire resistance temperature of Class B is 750 ~ 800℃. Take NH-YJV refractory cable of mica tape/crosslinked polyethylene composite insulated polyvinyl chloride sheathed power cable (specification is 0.6/1KV4×240+1×120) as an example, this cable is not armored, compared with other refractory cables, easy to bend, convenient laying. The high rated temperature of the cable conductor that allows long-term operation is 90℃. The short-circuit temperature of the special cable conductor can reach 250℃, and the duration is not more than 5 seconds. Its refractory ambient temperature is generally 700 ~ 800℃, which can maintain 1.5 hours of transmission operation. Its carrying capacity is generally about 450A current, laying when the trend is more flexible. When the transmission current reaches more than 1000 amperes, the number of fire-resistant cables increases more.