A Study on the Life Estimation and Cavity Surface Degradation Due to Partial Discharges in Spherical Cavities within Solid Polymeric Dielectrics Using a Simulation Based Approach

Partial Discharges (PD) in cavities are responsible for the greatest ageing rate in polymeric solid dielectrics due to chemical and physical deterioration mechanisms activated by the charge carriers, Ultra Violet (UV) radiation and local temperature rising during PDs activity. From the above, it is necessary to develop prognosis tools based on PDs measurements as diagnostic quantities in order to infer the time-to-breakdown, life, of solid dielectrics for improving the reliability of electrical assets, especially in current applications where they are subject to great electrical stresses in voltage frequency and magnitude. In this paper, the degradation in polymeric materials induced by PDs in cavities is briefly discussed from a phenomenological point of view, and then it is quantitatively evaluated using a simulation-based approach and a new proposed damage function. The time-to-breakdown calculated from simulations exhibits good agreement when compared with experimental measurements. Additionally, an analysis on the effect of the magnitude and frequency of the applied voltage on the degradation rate is also presented and the effectiveness of a degradation indicator, proposed by other authors, is evaluated under different stress conditions.

Automated summary

Partial discharges in cavities cause the highest aging rate in polymeric solid dielectrics due to various deteriorating mechanisms activated by charge carriers, UV radiation, and temperature rise during discharge activity. Developing diagnostic tools based on PD measurements is necessary to predict the time-to-breakdown and improve the reliability of electrical assets subjected to high electrical stresses. The degradation induced by PDs in polymeric materials is discussed, evaluated quantitatively through simulations, and compared with experimental results, showing good agreement. Additionally, the impact of voltage magnitude and frequency on degradation rate is analyzed, and the effectiveness of a degradation indicator proposed by other authors is assessed under different stress conditions.