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Unformatted text preview: Progress In Electromagnetics Research, PIER 104, 167–182, 2010 ELECTROMAGNETIC FIELD INTENSITY GENERATED BY PARTIAL DISCHARGE IN HIGH VOLTAGE INSU- LATING MATERIALS A. Bojovschi, W. S. T. Rowe, and K. L. Wong Electrical and Computer Engineering RMIT University Melbourne, VIC 3001, Australia Abstract —Partial dischagre is the precursor of insulators breakdown. In this work the propagation of electromagnetic radiation emitted from partial discharge in high voltage insulating materials is investigated. Three common dielectric materials used in power industry: polymer, epoxy resin and ceramics are studied. The results obtained are envisaged to support the development of appropriate sensors for partial discharge detection. The radiation pattern is dependent on a multitude of parameters. Among these, the intensity distribution of the source as well as the dielectric material and its geometry are the main parameters. Significant differences in the radiation spectra are obtained for insulators made of ceramic material compare to non- ceramic insulators. 1. INTRODUCTION Erosive discharges are also named Partial Discharge (PD) in high voltage (HV) technology [1,2] and can cause failure of HV components such as capacitors, cables and inlet bushings. PD that appears inside and outside of insulating materials is a persistent problem in power industry. An internal PD is initiated in fault like cavities within insulating material while external PD occurs at the the metal-insulator interface. Both kinds of PD represent the same discharge type. This discharge is known as Townsend electron avalanches which can develop into streamers and micro-sparcs [3,4]. Diverse electromagnetic (EM) techniques were proposed for detection and monitoring of partial discharge activity in high voltage infrastructure [5,6]. These methods Corresponding author: A. Bojovschi ([email protected]). 168 Bojovschi, Rowe, and Wong employ EM sensors to detect the radiation emitted from PD activity and it has been shown to provide valuable information on the condition of insulators. The propagation of EM radiation in isotropic media has been well explored . Furthermore the development of the Finite Difference Time Domain (FDTD) method allows an accurate investigation of EM fields in diverse dielectric media . Recent works use FDTD to simulate the propagation of EM radiation emitted from PD on a distribution power line . The radiation spectra along the line and in the proximity of PD source was investigated for detection purposes. Radiation spectra of PD in dielectrics showed that the EM radiation propagates in HV insulating materials as dipoles or multipoles . Different radiation patterns within distinct dielectric materials correspond to a different power density. The improvement of PD detection techniques rely on an accurate interpretation of the EM spectra emitted from discharge zones. A study of coupling between the EM radiation, generated by PD, and electric or electronic systems...
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