The performance characteristics of fireproof cable

Insulation resistance The insulation resistance of fireproof cables depends to a large extent on the moisture content in the magnesium oxide. Under standard conditions, when the humidity does not exceed 0.4% (allowable value). The insulation resistance of compressed magnesium oxide is higher than that of other insulating materials (such as PVC, PE, XLPE, etc.), and it can reach 10Ψ/m~1016Ψ/m at 20 °C.

The performance characteristics of fireproof cable

The insulation resistance of the cable is related to the number of cores and the size of the cross section. The larger the number of cores, the larger the cross section. The smaller the insulation resistance, at the same time, the insulation resistance also depends on the form and amount of impurities in magnesium oxide. The relationship with temperature is also extremely important, the higher the temperature, the lower the insulation resistance of the cable.

The electrical strength is compared to other insulating materials used in the cable industry. The electrical strength of magnesium oxide insulated finished cables is not high, and the electrical strength of finished cables depends on the density of magnesium oxide. Insulation thickness and the state of the cable specimen itself when the cable is subjected to a sharp bend. The density of the insulating material at the bend will decrease, and cracking will occur in severe cases. This leads to a decrease in the electrical strength of the cable, and tests have shown that at a temperature of 20°C. When the frequency is 50Hz, the electrical strength of the standard density cable is close to 6.0MV/m when it is not bent. The bent cable has a cable strength of about 3MV/m when the bending radius is 6 times the cable diameter.

Heat resistance of cables The heat resistance of fireproof cables depends on the allowable operating temperature of the core and sheath during operation. At high temperature, neither the wire core nor the copper sheath will be oxidized, because the oxygen content in the cable insulation is very low. The core oxidation is not serious, but the cable jacket is oxidized violently due to exposure to the air medium. The higher the temperature, the more serious the oxidation. When the temperature of the copper sheath of the cable exceeds 250 °C, rapid oxidation begins to occur, forming an oxide layer of CuO, which reduces the thickness of the sheath.