Wire and cable insulation and sheathing layer made from organic material, when the temperature exceeds a certain range, these materials will burning.

Since wires and cables long-term loading, the heat of the conductor will result in the insulating and sheath layer aging. If always overload, will accelerate its aging.  Unqualified insulating material and immature production also will accelerate aging.

Once wires and cables was aging, will breakdown and cause the interphase short-circuiting. A large interphase short-circuiting will get a high temperature of several thousand degrees within a very short time, it can make the surrounding combustibles burning.