What is mi cable? mi cable fire rating and mi cable resistance?
What type of cable is Mi cable? Mi cable is BTTZ cable, mainly used for power supply of fire control system, belongs to mineral insulated cable; The Mi cable fire resistance rating is the highest of any cable.

1.What is Mi cable?

In the fire protection design code of building engineering, the fire protection system must use mineral insulated cable. Mi cable is one type of mineral cable, and others include yttw, btly(ng-a), BBTRZ, etc. It is composed of copper core, copper sheath and magnesium oxide insulation material. It is a real fireproof cable, which can keep the normal power on for more than 3 hours in the fire from 950℃ to 1000℃.
BTTZ cable model: BTTZ (q), BTTZ (y) z(q), wd-bttz(q). Z and q are cable rated voltage z: 750V for heavy duty, q: 500V for light duty; The following is the meaning of the type of BTTZ cable:

Z/Q-- outer sheath: PVC -V, PE-Y
T - copper conductor
T - copper sheath
B-- wiring with fixed power cable
Mi cable structure drawing
Fireproof cable is mainly composed of copper conductor with high conductivity, mineral (magnesium oxide) insulation material and seamless copper tube sheath. When the cable is used for copper corrosion occasions, the outermost layer is added with a layer of anticorrosive protection outer sheath (optional).

2.Mi cable fire rating

The long-term working temperature of mineral insulated cable is 70℃. In the case that nobody touches it, the long-term working temperature of mineral insulated cable is 105℃. In the case of special high temperature, the long-term working temperature can be 250℃ or below. The power can be supplied for more than 3 hours at 950-1000℃, and the working temperature for short or very short time can reach 1083℃.
BTTZ mineral insulated cable has passed the CWZ class in the BS6387 fire protection standard certification, and the following fire spray impact tests have been performed on a sample. The fire resistance of BTTZ cable is shown in the figure below:
Mi cable fire rating

3. What is the resistance value of Mi cable?

The BTTZ cable resistance can be measured by 500V meter. The Mi cable resistance can only be used if it is larger than 100 megohm. If it is not reached, it may be affected by damp. Special attention should be paid to the multi-core BTTZ cable terminal head. During the installation process, the spacing and insulation between the wire cores, the wire cores and the copper sheath should be ensured. Once the cable is installed at the terminal head and the intermediate head, another insulation shake shall be performed. In the actual measurement, the pointer of megohm meter should point to infinity, which means the cable line performance is good. If a decrease in resistance is found during measurement, the fault point should be found. Usually, the fault point is at the junction. At this time, the joint should be removed and dehumidified until its insulation resistance is restored, and then the joint should be made again.