چكيده به لاتين
Abstract:
Nowadays polymeric insulations are the most widely used insulation materials in high voltage equipment like cables because of their numerous advantages in terms of electrical performance. On the other hand, these insulation materials are prone of degradation due to the occurrence/existence of voids, cracks, and electrical trees. Electrical treeing as a pre-breakdown phenomenon in dielectric materials has a remarkable contribution in polymeric insulation failure. So this thesis has focused on modeling and identification of electrical tree growth because of its importance in the process of insulation degradation.
Deep understanding of any phenomenon and its effective factors, has significant role in more accurate modeling of that phenomenon. However simplifying assumptions can be considered to implement the model practically. Therefore in this thesis a comprehensive review about physics of electrical tree mechanism (including inception, propagation and breakdown phases in electrical tree process) and some effective factors on both beginning and growth of electrical tree in polymeric insulation materials has been done and then available models for electrical tree has been classified in three general categories: experimental, mathematical and electrical (including circuit and field types) models. In this thesis circuit models have been used to model electrical tree growth because of their advantages, including low calculation burden and simplicity of analysis in comparison with other models. Since available circuit models neither have sufficient accuracy and physical feasibility nor can model electrical tree growth dynamically, a new circuit model is proposed and validated to overcome these disadvantages.
In sequel, the best energy based index among the foregoing features has been extracted and used to identify the only defective cable section in a cable network. Also some fixed criteria based on the best energy index have been introduced to identify electrical tree growth; in a discrete set of lengths.
Keywords: Electrical tree growth modeling, Identification of electrical tree growth, Energy index, Partial discharge, Polymeric insulations.
