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

Abstract

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.

Parameters that influence the partial discharges occurrence in cavity defect within electrical cable insulation

“…Therefore, the type of gas contained or composition of the gas trapped in the defect of the cavity influences the life of the insulation by participating in the appearance of partial discharges in this later and which reflects clearly the influence of the chemical aspect in the partial discharge mechanism. In addition, our result reflects the dielectric degradation by ionization impact across the gasinsulator interface which must be robust and antioxidant against any type of gas formed probably in the cavity defect by modifying the characteristics of the insulating material surface as confirmed by the literature cited in [13,14].…”

“…We will consider in this case that the cavity defect is filled with nitrogen because the latter can represent the air by the rate of 78 ٪ which is confirmed in [14]. Then we will impose our cable to an increase in voltage amplitude from 24KV to 38KV at time 5000 µs to see its influence on the appearance of PDs in the cavity defect.…”

“…24, No. 2 (2023) Elagoun A, Seghier T.: Parameters that influence the partial discharges occurrence in cavity defect within … 3 through the ionization parameters of the gas that vary according to its composition, to the charge drift or the rate of recombination and to the emission at the surface of cavity [13,14].…”

“…The induced degradation by the PD in the cavity defect is due to the chemical mechanisms during the PD event. It was found in [14] that the cavity surface was not degraded if the electric field is less than 2.28 kV/mm. This confirms and validates our result very well.…”

Tracking Resistance in Polymeric Insulation Materials for High-Voltage Electrical Mobility Applications Evaluated by Existing Test Methods: Identified Research Needs

“…Therefore, the hot electrons undergo rapid thermalization by DEA of C–H bonds and impact ionization. These cumulative effects can eventually cause irreversible insulation degradation [ 97 ].…”