Insulation performance with irreversible decline occurring in the course of time, called the aging of the insulation.
Insulation aging of the form of various aspects, such as the increase of dielectric loss tangent, low breakdown strength, mechanical strength, or other performance.
The cause of insulation aging is complex, there is electricity aging and thermal aging, chemical and mechanical aging, aging and be affected with damp be affected with damp and pollution, and so on. These reasons may exist in the insulation, or from one form into another form of ageing, it is often difficult to be separated from each other.
In the process of aging, the insulation performance to the provisions under the allowable range of the time required to commonly referred to as insulation Life.
Usually the performance over time and the curve of the aging of the insulating material called aging curves or life curves.
The breakdown voltage of the cable and voltage time relationship is one of the most important life curve.
Long-term operation test by cable or cable life curve of the accelerated aging test, is an important basis for design of cable