What are the main categories of domestic mineral insulated cables?
■ Rigid mineral cables. Domestically, these cables are known as BTTZ (Q) copper-core copper-sheathed cables. They are constructed with copper rod as the conductor core, magnesium oxide filler as insulation, and copper tube as the sheath, produced through repeated high-temperature drawing. Invented by the Swiss in 1896, these copper-core copper-sheathed cables offer high current carrying capacity, but due to the technological conditions at the time, their product structure had historical limitations.
■ Flexible mineral insulated fire-resistant cables. Domestically, these cables are known as BBTRZ (Q) flexible mineral insulated fire-resistant cables. They use stranded annealed copper wire as the conductor and inorganic mineral alloy mica tape and mineral compounds as insulation and sheath. Invented by the Swiss company Stud in 1984, these flexible mineral insulated fire-resistant cables inherit the fire-resistant and high current carrying capacity characteristics of BTTZ cables while significantly improving upon their inherent structural deficiencies.
■ Other transitional mineral insulated cables. Between the above two types of mineral cables, China has successively developed transitional metal sheathed, copper stranded structure flexible fire-resistant cables such as YTTW, BTLY, HFTGB, and quasi-flexible or semi-flexible mineral insulated cables. However, these structures have not appeared internationally, and the "China Fire Protection Manual" has not included these products.
