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Improvement of Partial Discharge Detection Methods in High Voltage Insulation Systems Through Physical Study and Modeling of the Partial Discharge Phenomenon

Vasigh Zadeh Ansari, Arman | 2025

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 58554 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Vakilian, Mehdi; Ghorbanzadeh, Atamalek
  7. Abstract:
  8. High-voltage equipment used in the power industry operates under intense electric field stress. Due to the presence of strong electric fields, the insulation systems of such equipment gradually experience partial discharges. Investigating the phenomenon of partial discharge is often accompanied by several challenges. Initially, because the occurrence of this phenomenon is closely related to atomic and molecular physics as well as electron generation within insulating materials, it is necessary to consider the complexities of media containing charged particles. In this dissertation, the phenomenon of partial discharge has been studied based on physical principles and theoretical approaches. Methods are presented for determining the distribution of electric potential within media containing charged particles, an essential aspect for analyzing the conditions under which partial discharges occur. Furthermore, key aspects of partial discharge signal detection and the influence of physical parameters on signal detection are investigated. For example, through the derivation of theoretical relationships and validation by experimental measurements, it is demonstrated that the capacitive characteristics of an antenna used for detecting partial discharge signals in the vicinity of high-voltage equipment can significantly affect the distortion and phase of the received signals. Moreover, a novel approach is proposed for estimating the spatial distance to the location of partial discharges in cable distribution systems. This method is based on phase-resolved partial discharge (PRPD) patterns and employs real industrial data for validation. In addition, a statistical analysis is presented for the behavior of electron avalanches generated during partial discharges. For the first time, a discrete probability density function (PDF) of the number of electrons within a given discharge length has been derived, enabling comprehensive statistical characterization of partial discharges during the electron avalanche process. The derived function has also been validated using experimental data reported for the Townsend discharge profile. Finally, two important practical topics have been examined: 1) A method is proposed for estimating the expected charge of partial discharges during the insulation design stage, prior to construction. This is crucial because a computational tool is needed at the design stage to ensure that the predicted partial discharge levels remain below the corresponding standard limits. 2) Concepts for measuring and calibrating the displaced charge in partial discharge phenomena using nontraditional detection methods are introduced and experimentally verified. It is shown that in classical partial discharge calibrators, the amount of charge injected into the circuit depends on the impedance seen by the calibrator. Therefore, in the design and construction of partial discharge calibrators, the output voltage level must be adjustable according to the equivalent impedance of the connected circuit. Additionally, a computational method based on Laplace transformation and regression analysis is introduced, enabling indirect (non-contact) measurement of the partial discharge charge. This approach can thus be used for calibrating partial discharge measurement instruments
  9. Keywords:
  10. Partial Discharge ; Calibration ; Modeling ; Electric Load ; Non-Conventional Measurement Methods ; Statistical Study ; Electron Avalanche

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