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Generally, UHV converter transformer bushing cores use epoxy resin and insulating paper composite materials as the main insulating dielectric. It is necessary to study the space charge behavior of epoxy resin/insulating paper composites at high temperature and field strength. According to the insulation structure of dry-type bushing core, two epoxy/paper/epoxy three layers Composite samples with different...
The flashover of insulators is a bottleneck for the development of gas insulated transmission line (GIL). The operation experience of GIL shows that metallic particle plays an important role in flashover of the insulator. An experiment platform was established to study the influence of gas pressure on the flashover characteristics of the post insulator in SF6 under negative DC voltage. The impacts...
Polyethylene is often used as insulation in HVDC cables. In order to reduce charge injection and thus increase cable time life, various interface barriers, such as fluorination, or bulk barriers, such as nano-filler compounds, can be used to modify the material properties at the atomic scale. At the atomic scale, the energy gained by an electron subjected to an electric field depends on its mean free...
In the field of electrical insulation, polymers are replacing progressively formerly used materials. When such an insulator is subjected to a voltage gradient, an internal space charge and a polarization develop, eventually reducing the apparent electrical strength of the material. We have applied the pressure wave propagation method to the analysis of the phenomenum in polyethylene. The spatial charge...
Epoxy resin has been widely used in dry-type insulation application such as DC dry-type bushings. In practice, DC dry-type bushings work not only under DC voltage, but also under multiple harmonics with 50Hz fundamental frequency. This study focuses on the effects of space charge behavior of epoxy resin on real voltage of DC dry-type bushings. By using Fourier decomposition, the real voltage of DC...
The effect of electrode material on the space charge behavior in epoxy resin has been investigated using the pulsed electro-acoustic (PEA) technique. Common metallic electrode materials, i.e. gold, silver and copper, were selected and sputter-coated on the specimens, and the space charge dynamics after the application of various electric fields were monitored at 293 K and 313 K. The space charge accumulation...
The evolution of the space charge distribution in polypropylene including non-uniform distribution of talc fillers is studied. In the process of fabrication, a lack of fillers is clearly localized in the middle of the material which introduces a macroscopic heterogeneity. Under voltage, it acts as a macroscopic trap that imposes an alternating charge buildup, leading therefore to a limited electric...
The treeing phenomena are well known as an initiation process of electrical breakdown in the electric power cables. It is discussed that the charge injection from electrode is related to the growth of the tree. The space charge measurement technique by the pulsed electro-acoustic (PEA) method is widely used. However, the measurement technique in the non-uniform electric field has not been realized...
This work shows that the discharges pattern and final length, Lf, of creeping discharges depend on the amplitude and polarity of the voltage, the type of gas (mixture) and pressure similarly as in the case of the materials we investigated previously. Lf is longer when the point is positive than when it's negative; this is likely due to the influence of space charge on the electric field. Lf increases...
A universal feature of practical importance in the breakdown of solids, liquids, gases and vacuum is the sensitivity or otherwise of these media to breakdown due to the effects of imperfections in the dielectric and electrode system. High local electric stresses adjacent to protrusions or edges of electrodes can lead to self-propagating failures in the insulating medium. This paper discusses the occurence...
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