Electrodamage mechanics of dielectric ageing

In this study we introduce a damage mechanics concept of ageing in solid dielectrics. The key elements are an electro- damage parameter and an electrodamage evolution kinetic equation. We show that the ageing process of dielectrics could be generally looked on either as an accumulation of electrodamage toward a maximum tolerable value or as an exhaustion of the lifetime inherent in the dielectric, and the nature of the ageing is that electrodamage accumulates gradually in the course of stressing time and breakdown occurs when these reaches a critical level. As a further exploration to develop a mechanisms-based electrodamage evolution theory, nonequilibrium statistical physics has been used to establish a statistical theory of electrodamage. The growth of microscopically electrodamaged regions is regarded as the elementary process of electrodamage to the dielectric and the electrodamage parameter is universally defined as the failure probability of the insulation due to the growth of the electrodamaged regions. From the evolution equation of electrodamaged regions, a partial differential equation that universally describes the evolution of the electrodamage parameter is derived. Taking the example of water treeing in polymeric insulators the application of the proposed theory has been addressed.