Ng-a (btly) series isolated fire-resistant ACSR Cables are flame-retardant and fire-resistant cables. The insulating layer is phlogopite tape (fire resistance temperature 750 ℃ ~ 800 ℃), the sheath is aluminum tube (fire resistance temperature 660 ℃), and the outer sheath is plastic. It is not in the same category as yttw and bttz mineral insulated cables. We can make a comparison from the following technical data.
The structure diagram of yttwy copper core copper sheathed mineral insulated cable and ng-a btly isolated (flexible) mineral insulated cable is as follows:
(1) Yttw series metal sheathed inorganic mineral insulated cables are fireproof cables composed of copper core, copper sheath and inorganic mineral insulating materials. They are produced in strict accordance with the national industrial standard JG / t313-2014.
1) Yttw series metal sheathed inorganic mineral insulated cables are wrapped with natural inorganic mineral insulating tape (high temperature resistance above 1370 ℃). The sheath adopts copper sheath (high temperature resistance of 1083 ℃), which is continuously rolled, has fast heat dissipation and can be bent.
2) Metal sheathed inorganic mineral insulated cable can be made into pre branch cable to realize trunk power distribution system.
(2) Ng-a (btly) series isolated fire-resistant ABC Cables are organic and inorganic mixed fire-resistant cables, which will produce low smoke and low toxicity during combustion, which can not be compared with the smokeless and non-toxic of inorganic mineral insulated cables.
1) The refractory layer is made of glass fiber cloth, which is softened and damaged at about 840 ℃;
2) The filling layer adopts hydrated metal oxide, which is a gypsum like semi fluid containing organic components. During combustion, water vapor escapes and colloidal becomes solid (aluminum oxide). It is unclear whether it is toxic or not;
3) The isolation sleeve is generally cross-linked polyethylene (XLPE), with low smoke and low toxicity during combustion;
4) The metal sheath and aluminum material have poor mechanical and electrical properties. The flame temperature melts at 660 ℃, so it is not suitable for the metal sheath of fireproof cable;
5) The mineral insulation layer adopts phlogopite tape. The fire resistance characteristic of phlogopite is only class B (750 ℃ ~ 800 ℃), which can only be used as class B fire-resistant cable. It cannot be used in class A (950 ℃ ~ 1000 ℃) fire-resistant cables.
To sum up, yttw series metal sheathed inorganic mineral insulated cable has the following essential advantages compared with ng-a btly
a. The cable structure shall be free of any combustible organic material;
b. The high temperature resistance of the cable is greatly improved, and the calorific value is zero;
c. The cable is non combustible as a whole;
d. Non toxic and smokeless during cable combustion;
e. The thermal overload and long-lasting withstand voltage performance of the cable are greatly improved;
f. The durability of the cable has doubled.
Moreover, there is no unified standard for ng-a (btly) series isolated fire-resistant cables in China, and only individual manufacturers produce them according to enterprise standards.