There are many different environmental and operational conditions which are likely to influence the longevity of electrical cables in service.
The insulation and sheathing materials of cables may degrade over time when exposed to heat, UV light, ozone, various chemicals, excessive flexing, or mechanical action, not to mention in certain situations cables may be exposed to attack by termites and rodents.
When a current passes through the cable conductor it generates heat – the higher the current the more heat will be generated. This will have a significant impact if the conductor is undersized or continuously at or near the cable’s maximum permissible (rated) load, degrading the insulation and sheathing materials over time until they become dangerous and require replacement.
Although it is primarily the condition of the insulation and sheathing materials rather than the actual conductors that determine the longevity of the cables, water ingress, and poor fixings can also cause corrosion and damage.
The standards that cables are manufactured to do not specify a particular life expectancy. Some cable manufacturers will determine a likely life expectancy based on typical conditions. For example, a household fixed wiring cable with typical electrical loading, wired using the appropriate wiring guidelines, could be expected to last 20 years. However, in some cases cables which have not been used excessively have been found in relatively good condition up to 50 years after installation.
There are many different environmental and operational conditions that are likely to influence the longevity of electrical cables in service.