The service life of power cables is not a fixed value, but is comprehensively affected by multiple factors including material type, operating environment, load condition and installation quality. Generally speaking, the replacement cycle of power cables ranges from 15 to 30 years, but the specific judgment should be made based on actual conditions.

I. Typical Service Life of Different Types of Cables

The design life of ordinary PVC insulated cables is usually around 15 to 25 years. This type of cable is low in cost, but has a low temperature resistance grade, and its long-term operating temperature should not exceed 70°C. Its aging speed will be significantly accelerated under high temperature or overload conditions. Cross-linked polyethylene insulated cables have better performance, with a design life of 20 to 30 years. They have a high temperature resistance grade up to 90°C and large current-carrying capacity, making them the mainstream products in current engineering projects. Mineral insulated cables are entirely made of inorganic materials, with a theoretical service life of 50 to 100 years, which can even be as long as the service life of the building, on the premise of reliable installation quality and no external force damage. The service life of aluminum alloy cables is generally 20 to 30 years, which is equivalent to that of cross-linked polyethylene cables.

II. Key Factors Affecting Cable Service Life

‌Operating temperature‌ is the most critical factor affecting cable service life. Studies have shown that for the insulating material of cables, every 10°C rise in operating temperature will roughly double the aging speed. Long-term overload operation and poor heat dissipation conditions (such as dense laying of multiple cables and poor ventilation in cable trenches) will lead to temperature rise and greatly shorten the service life of cables. Environmental factors are also equally important. Humid environment will allow moisture to invade the insulating layer and accelerate insulation deterioration; corrosive environments such as acid-base salt spray and chemical gas will erode the cable sheath and armor; long-term ultraviolet radiation will make the insulating layer of exposed cables brittle and cracked. Mechanical damage is also a common cause. Hidden damage during construction, external force excavation damage and long-term vibration will all shorten the actual service life of cables. In addition, voltage level also has an impact. The insulating layer of high-voltage cables bears higher electric field strength, so the aging speed is relatively faster.

III. Signs Requiring Immediate Cable Replacement

When the following conditions occur to the cables, replacement should be arranged as soon as possible: obvious cracks, damage, discoloration or hardening and brittleness appear on the insulating layer; the conductor is exposed or severely oxidized; the cable joint generates frequent overheating and gives a burnt smell; frequent tripping or action of the residual current device occurs during operation; when the insulation resistance is measured with a megohmmeter, the resistance value is significantly lower than the initial value or below the specified lower limit (the insulation resistance of low-voltage cables should generally not be less than 0.5 megohms); the outer sheath of the cable is bitten by rats or corroded and perforated. In addition, it is recommended to replace all cables synchronously during the renovation of old houses or factories, so as to avoid the risks brought by the mixed use of old and new cables.

IV. Regular Inspection and Maintenance

In order to accurately judge whether the cables need to be replaced, regular preventive inspection is recommended. Use an infrared thermal imager to detect the temperature of cable joints and the cable body every year, and take treatment when the abnormal temperature rise exceeds 60°C; measure the insulation resistance regularly and compare with historical data to judge the trend; carry out partial discharge detection on important lines, and deal with anomalies in time. Through scientific inspection and maintenance, potential problems can be found in time, and replacement can be arranged before the cable completely fails, so as to avoid losses caused by sudden failures.

Summary‌: The replacement cycle of cables is generally 15 to 30 years, but the actual service life is affected by factors such as temperature, environment, load and installation quality. Only through regular inspection, scientific maintenance, combined with appearance check and electrical test, can we accurately judge whether the cables need to be replaced and ensure the safety of power consumption.