محمد گودرزي

Aging an‎d loss of hydro‎phobicity are among the most significant challenges in using polymer insulators in polluted areas. These issues lead to an increase in leakage current an‎d the occurrence of dry-ban‎d discharges on the insulator surface, which may ultimately result in flashover an‎d fault occurrence. In this thesis, the aging of polymer insulators has been modeled using circuit an‎d finite element methods, an‎d approaches for the smart management of polymer insulator lifetime have been presented. The proposed methods are based on insulator leakage current an‎d can be implemented online for use in smart networks. For laboratory testing, insulators with different levels of aging—collected from the MV network—were used. These insulators were artificially contaminated, an‎d their leakage currents were measured at various contamination levels, serving as the basis for modeling.The proposed circuit model is based on measured leakage current signals. This model incorporates both the contamination layer an‎d dry-ban‎d discharge into its structure, an‎d it represents insulator aging through changes in the values of its elements. The high similarity between the experimental results an‎d the model outputs confirmed the model’s ability to capture the effect of aging on leakage current characteristics. Furthermore, mathematical equations for the model parameters were derived as functions of aging level using curve fitting. The wet contamination layer resistance parameter (Rs) effectively reflects the condition of the insulator, an‎d the lifetime of polymer insulators was estimated using the extracted equation for this parameter. In addition, in the case of discontinuous leakage current, discharge amplitude an‎d discharge duration were extracted from the leakage current signals an‎d introduced as two indices for eva‎luating polymer insulator aging. In this thesis, a new method for finite element modeling of contaminated polymer insulators is also proposed. In this method, the dry-ban‎d discharge phenomenon in the pollution layer, as well as the effect of insulator aging on the severity of this phenomenon, are incorporated. For this purpose, the electrical conductivity of the pollution layer is considered dynamic an‎d modeled as a function of the electric field at the insulator surface. The parameters of the conductivity–field curve were obtained through low-voltage experiments an‎d used in the simulations. The finite element modeling results are consistent with the experimental findings an‎d demonstrate an increase in the intensity of dry-ban‎d discharge with increasing insulator age.

مقره پليمري , پيرشدگي , مديريت عمر , آلودگي , تخليه باند خشك , مدلسازي

polymer insulator , aging , life management , pollution , dry-band discharge , modelling

Mohammad Goudarzi

Ahmad Gholami