Browsing by Author "Mehmood, Basharat"

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    A Study of the Eroding Dry-Band Arcing on Silicone Rubber Insulation Using Ultra-High Frequency Detection Technique
    (University of Waterloo, 2025-04-25) Mehmood, Basharat
    Erosion of silicone rubber housing material is a major cause of failure in outdoor insulators used on overhead power distribution and transmission networks. Dry-band arcing, resulting from leakage currents on the insulator surface, is the main culprit of the erosion of silicone rubber housing material. The inclined plane tracking and erosion test, standardized in IEC 60587 and ASTM D2303, has been a key tool for testing outdoor insulating materials under dry-band arcing at the material development stage, enabling efficient material ranking for field applications. Extensive research on the erosion mechanism of silicone rubber has been carried out in the standard test, and accordingly, the reliable assessment of erosion has facilitated the development of formulations with acceptable performance for outdoor insulation applications. The degree of erosion of silicone rubber varies depending on the severity of dry band arcing during the inclined plane test, with highly severe arcing—referred to as critical or eroding dry-band arcing—often leading to deep erosion. The two inclined plane test standards specify different testing methods, range of test voltages, and failure criteria for the assessment of erosion on silicone rubber. However, the testing methods specified in the standards have often been used interchangeably in different studies, and there is no general agreement on which method is most appropriate for the reliable evaluation of erosion on silicone rubber. In addition, there are wide discrepancies in the selection of test voltages, and no unified agreement exists on the most suitable voltage level for testing silicone rubber materials, leading to inconsistencies in test outcomes. Another crucial aspect of the inclined plane test in evaluating the performance of insulating materials is identifying erosion failure, for which different criteria are specified in the two standards. However, the failure criteria specified in the standards are also applied inconsistently across various studies, with different criteria being used. While some criteria may be effective for certain materials, they are not always applicable to SR—particularly under DC voltages. These inconsistencies in testing methods, voltage selection, and failure criteria largely stem from a limited understanding of the erosion failure mechanisms of silicone rubber, highlighting a critical research gap that needs to be addressed. Additionally, the erosion mechanism of silicone rubber has been extensively studied in the inclined plane test based on leakage current techniques. While these methods correlate leakage current with dry-band arcing severity during the test, the onset of erosion or material failure could not be reliably detected with these techniques. In particular, no significant focus has been given to the erosion failure mechanisms on silicone rubber insulation under the eroding dry-band arcing. Consequently, the underlying physics of the eroding dry-band arcing driving erosion failure of silicone rubber remains inadequately understood, presenting a critical technical gap. This highlights the critical need for a reliable detection method of the eroding dry-band arcing to identify deep erosion failure during the inclined plane test. This thesis provides a mechanistic understanding of the erosion failure mechanisms of silicone rubber particularly through a reliable detection of the eroding dry-band arcing in the inclined plane test. To achieve this, ultra-high frequency detection of the eroding dry-band arcing is introduced as a reliable technique to identify erosion failure of silicone rubber in the AC and DC inclined plane tests. This detection method will serve as a foundation for improving the elucidation of the mechanisms of eroding dry-band arcing that drive erosion failure in silicone rubber. Moreover, it is a critical step towards improving the standards by introducing a clear erosion failure criterion for silicone rubber in the inclined plane test.