Cable aging is a slow cumulative process caused by the combined action of multiple factors, which eventually manifests as the decline of insulation performance, and even leads to accidents such as short circuits and fires. Understanding these causes helps us better prevent and replace aged cables in time.

I. Thermal Stress and Overload Operation

This is the most important cause of cable aging. Current will generate heat when passing through the conductor. Long-term overload operation of the cable or excessively high ambient temperature will lead to a continuous rise in the temperature of the insulation layer. Insulating materials will undergo thermal oxidative degradation at high temperatures, with molecular chains broken and performance dropping sharply. Studies show that for every 10°C increase in temperature rise, the insulation aging rate approximately doubles. Especially during the peak power consumption in summer, excessively high temperature can easily break through the weak points of cable insulation.

II. Electric Field Effect and Partial Discharge

Under the long-term effect of electric field, partial discharge may occur inside the cable insulation layer. This tiny discharge will continuously erode the insulating medium, form dendritic carbonization channels, and gradually reduce the insulation strength. Weak parts such as cable joints and terminals are more prone to partial discharge due to uneven electric field distribution, and become high-incidence points of aging faults.

III. Mechanical Damage and External Force Destruction

This is a common direct cause of cable faults. Non-standard construction during laying and installation, such as too small bending radius and excessive stretching, will damage the insulation layer. Civil construction above directly buried cables may also accidentally damage the cables by machinery such as excavators. Even if the damage is not serious at that time, after months or even years of operation, the damaged part will gradually expand and eventually break down to cause a fault.

IV. Environmental Factors and Chemical Corrosion

The environment where the cable is located has a huge impact on its service life. Humid environment will make moisture invade the insulation layer, form water trees under the effect of electric field, and accelerate insulation deterioration. Chemical substances such as acid-base gas, salt spray and oil stain will corrode the outer sheath and armor of the cable, leading to the failure of the protective layer. Long-term ultraviolet radiation will make the insulation layer of exposed cables brittle and crack. The aging rate of underground cables in chemical industry areas or humid soil will be significantly accelerated.

V. Natural Material Deterioration and Manufacturing Defects

Even without external damage, the cable material itself will naturally age over time. The design life of ordinary PVC insulated cables is about 15 to 25 years, and the insulation performance will drop significantly after extended service. In addition, manufacturing process defects, such as uneven insulation layer thickness, containing impurities or bubbles, will also shorten the actual service life of the cable.

Summary: Cable aging is the result of the synergistic effect of multiple factors such as heat, electricity, machinery and environment. Regular inspection, avoiding overload and improving the operating environment are the key measures to delay aging and ensure electricity safety.