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- Chen, Xiangrong, 1982, et al.
(författare)
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Electrical Treeing Behavior of DC and Thermally Aged Polyethylenes Utilizing Wire-Plane Electrode Geometries
- 2014
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Ingår i: IEEE Transactions on Dielectrics and Electrical Insulation. - 1558-4135 .- 1070-9878. ; 21:1, s. 42-52
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents electrical treeing behavior in low density polyethylene (LDPE) and cross-linked polyethylene (XLPE) after exposure to thermal and DC electro-thermal ageing. Both the ageing and the treeing tests were performed by means of two different types of test objects with wire-plane electrode geometry. One type of the tested objects contained only wire electrode of 10 µm diameter, whereas in the other type the wire electrode was attached through a semiconducting tab. The ageing was performed at 80°C with and without 10 kV DC voltage of both polarities connected to the wire and lasted up to 800 hours. The AC electrical treeing tests were applied afterwards for detecting changes of material properties after the ageing. The results showed that the electrical tree inception voltage consistently decreased with increasing time of thermal exposure, whereas the applied DC electric stress had a negligible effect on the observed behavior. Similar effects were found in both the tested materials (LDPE and XLPE) though the object type also influenced the results. For the objects with semiconducting tab, a higher level of the scale parameter was registered because of shielding effect of the tab on the electric field strength at the wire electrode. It also yielded less number of trees growing in parallel at the electrode. The dominant effect of thermal stress on the ageing of LDPE was elucidated by using various analytical techniques, like differential scanning calorimetry, infrared spectroscopy, inductively coupled plasma optical emission spectrometry and oxidation induction time, and it is believed to mainly affect antioxidant content in the test objects.
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| 2. |
- Chen, Xiangrong, 1982, et al.
(författare)
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Nonlinear Time Series Analysis of Partial Discharges in Electrical Trees of XLPE Cable Insulation Samples
- 2014
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Ingår i: IEEE Transactions on Dielectrics and Electrical Insulation. - : Institute of Electrical and Electronics Engineers (IEEE). - 1558-4135 .- 1070-9878. ; 21:4, s. 1455-1461
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents an investigation into the nonlinear dynamics characteristics of the partial discharge (PD) sequence measured during the propagation of typical electrical trees in XLPE cable insulation. Calculation of the correlation dimension and the largest Lyapunov exponent from the PD sequence is used to illustrate the nonlinear characteristics of the PD behavior in the electrical tree growth. The results provide strong evidence for the existence of deterministic chaos in the PD phenomenon of electrical trees, where the correlation dimension and the largest Lyapunov exponent are related with the PD activity of the tree growth, rather than a presence of random stochastic process. The fluctuating correlation dimension of the PD sequence during the branch-pine tree growth is associated with the transition of PD patterns and the change of the channel conductivity of the tree structure. It is also found that the nonlinear dynamics characteristics of the PD sequence are influenced by the applied voltage, the channel conductivity and the electrical tree shape. A possible mechanism is presented for the formation of different chaotic extents of typical electrical trees in XLPE cable insulation.
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