When a conductor carries a current beyond its carrying capacity, the temperature of the conductor increases. As the temperature increases, the resistance of the conductor also increases, which results in a decrease in the carrying capability of the current. If the conductor continues to carry a current beyond its new carrying capacity, the temperature of the conductor will continue to rise. In extreme cases, the temperature of the conductor can rise to a level at which it is hot enough to ignite the surrounding environment or insulation material, potentially causing fire hazards.
When the temperature of a conductor rises to a certain degree, its current-carrying capacity will drop to zero, indicating that it will no longer be able to carry any current. This is because at high temperatures, the resistance of the conductor becomes extremely high, making it difficult for current to flow through it. If the current is forced to flow under such circumstances, the conductor will suffer severe heat damage, possibly melting or producing sparks, leading to serious accidents.
Therefore, once the current-carrying capacity of a conductor drops to zero or below, it must be immediately de-energized and checked and repaired. It is necessary to reasonably control the current-carrying capacity of the conductor when designing and using the circuit to avoid dangerous situations. Moreover, when selecting and configuring the conductor, various factors such as the characteristics of the conductor, the working environment, the work and electricity supply time, the stability and safety of electrical equipment, and other factors need to be considered comprehensively to ensure the safe and reliable operation of the circuit and equipment.