IEEE Task Force Report: Brittle Fracture in Nonceramic Insulators
ABSTRACT A description of the composite insulator brittle fracture phenomenon suitable to allow correct diagnosis of a failure is provided. The paper reports on the number of brittle fractures that have occurred around the world and contains specific empirical data surrounding composite insulator brittle fractures in the United States. It also includes several case studies of in service failures to inform the reader of the diversity of initiating causes. The current state of knowledge on the brittle fracture mechanism is presented. Based on what was learned during the study, possible actions that can be taken by manufacturers and users to reduce frequency of occurrence are suggested.
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ABSTRACT: Epoxy nanocomposites prepared by casting epoxy reinforced with silica flour and stiff spherical alumina nanoparticles were investigated for its electrical, mechanical, and thermal properties as well as morphological behavior and the role of interfacial interaction between nanoparticles and the matrix on these properties. It was observed that the dielectric breakdown of the cast epoxy system is affected by interfacial interaction between nanoparticles and epoxy chains at room temperature. However, dielectric strength significantly changes at different temperatures. Also, it was realized that the interaction between nanoalumina and epoxy chains dominate the mechanical properties of the system such as tensile and flexural strength. However, thermal properties of the nanocomposite were mainly affected by the matrix and the degree of crosslink density between chains.IEEE Transactions on Nanotechnology 09/2012; 11(5):957-963. · 1.80 Impact Factor
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ABSTRACT: The water absorption characteristics of a HTV silicone rubber material were investigated at different relative air humidity (RH). The two-sided water absorption process into disc-like HTV samples at different RH can be described by a Langmuir type diffusion model. The permeation process of water vapor through HTV discs was quantified by adjusting different constant RH at both sides of the discs. The permeation coefficient of the HTV discs amounts to an almost constant value of 10-7g cm-1s-1cmHg-1 at RH higher than 60%. Finally, a simplified model is introduced by what the water vapor permeation process into an air filled interface defect inside a composite insulator can be simulated.Electrical Insulation (ISEI), Conference Record of the 2012 IEEE International Symposium on; 01/2012
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ABSTRACT: This paper presents a novel artificial neural network (ANN)-based near-field microwave nondestructive testing technique for defect detection and classification in nonceramic insulators (NCI). In this paper, distribution class 33-kV NCI samples with no defects, air voids in silicone rubber and fiber glass core, cracks in the fiberglass core, and small metallic inclusion between the fiber core and shank were inspected. The microwave inspection system uses an open-ended rectangular waveguide sensor operating in the near-field at a frequency of 24 GHz. A data acquisition system was used to record the measured data. ANN was trained to classify the different types of defects. The results showed that all defects were detected and classified correctly with high recognition rates.IEEE Transactions on Instrumentation and Measurement 01/2014; 63(2):260-266. · 1.36 Impact Factor