Abstract
Insulated tubular busbar is a new type of current-carrying equipment with excellent performance. However, the research on this equipment is insufficient because of the short application and the lack of technical digestion, which has resulted in many accidents. In this paper, the full-scale model of epoxy-impregnated-paper insulated tubular busbar with bubble defects was designed and produced, its electrical breakdown process was investigated by withstand voltage test. In the experiment, the failure mode of breakdown caused by gas expansion was found for the first time. The research showed that the electrical-mechanical breakdown process could be divided into two stages: gas increase stage and breakdown threshold stage. The research also obtained the characteristics and the change criterions of the two stages. The gas in the bubble defects generated from epoxy decomposition which caused by partial discharge. When the gas pressure exceeds the critical fracture toughness of the bubble defects wall, the unstable crack extension occurs, therefore, improving the ability about resistance to partial discharge of epoxy resin or improving the fracture toughness of epoxy resin by modifying would enhance the breakdown performance of insulated tubular busbar. The result also has reference significance for other epoxy-impregnated-paper insulated electrical equipment.
Highlights
Insulated tubular busbar is a new type of busbar product coated with solid insulation, which use tubular copper as the conductor
By referring to the data related to the electrical breakdown process, this paper finds that the previous research objects are mostly epoxy resin and crosslinked polyethylene flaky samples, and the research ideas and results may deviate from the actual power equipment
It is difficult to detect when the sample transfers to the breakdown threshold stage by the traditional non-destructive detection method. Whether it is in the partial discharge measurement result or the appearance test of the sample, it is hard to find this phenomenon, which namely explains the frequent failure of tubular current and shows the importance of studying the electrical breakdown process of insulated tubular busbar from the internal process
Summary
Insulated tubular busbar is a new type of busbar product coated with solid insulation, which use tubular copper as the conductor. The insulation structure of the insulated tubular busbar is a composite system of epoxy resin impregnated paper. EXPERIMENTAL SETUP The insulation system, structure size and production process of the defect samples in the paper are as follows: the tubular conductor is made of T2 copper, and the main insulation structure is epoxy-impregnated-paper insulation system. The outer metal layer is wrapped around the semi-conductor screen and coated by the insulating paper to certain thickness. The key technology of sample production is epoxy resin impregnating paper in vacuum pressure, about 50 Pa . In order to study the process of the electrical degradation of the insulated tubular busbar, a transformer is used to perform electrical degradation on the long-term withstand voltage of the busbar sample. A gas chromatograph-mass spectrometer (Thermo Fisher) is used to analyze the gas composition and a scanning electron microscope (VE9800) for observing the dissected slice
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