Experimental Evaluation and Finite Element Modelling of the Effect of Aging on Dry-band Discharge Intensity in Polluted Polymer Insulators

Aging and loss of hydrophobicity are among the most significant challenges in using polymer insulators in highly polluted areas. This leads to an increase in leakage current (LC) and the occurrence of dry band discharge (DBD) phenomena on the surface of the insulator, which may ultimately result in flashover and fault. This paper investigates the effect of aging on the intensity of DBD in polymer insulators. To this end, five sample insulators of varying ages were collected from a medium voltage distribution network, and after applying artificial pollution, their LCs were recorded in a fog chamber under nominal voltage conditions. Additionally, magnitude and duration of discharge were extracted from the LC signals and proposed as two indices for evaluating the aging of the insulators. Furthermore, a novel method for finite element modelling of polluted polymer insulators is presented. In the proposed method, the phenomenon of DBD in the pollution layer and the effect of insulator aging on the intensity of this phenomenon have been implemented. For this purpose, the electrical conductivity of the pollution layer is considered to be dynamic and a function of the electric field at the surface of the insulator. The parameters of the conductivity-field curve were calculated through low-voltage test and utilized in the simulations. The results of the finite element modelling are in accordance with test results and demonstrate an increase in the intensity of DBD with insulator aging.