The mysteries of multifactor ageing

Ageing of solid insulating materials and systems, according to IEC and IEEE standards, is the occurrence of irreversible deleterious changes that critically affect performance and shorten useful life. What causes ageing is not an easy question to answer, nor is it a function of an isolated event or applied stress. Years of experience have shown that the degree and rate of ageing of insulation depend on the physical and chemical properties of the material, the nature and duration of applied/induced stress(es), and material processing and treatment during manufacturing and subsequent use in equipment. Stresses that affect the integrity, reliability, and service life of electrical equipment and components, such as switchgears, transformers, and cables, include electrical, thermal, mechanical, radiation and/or environmental ones. These stresses applied sequentially or simultaneously lead to ageing and deterioration, but the rates of ageing are different and are not easily explainable.<>