Journal ArticleDOI
Effect of tree channel conductivity on electrical tree shape and breakdown in XLPE cable insulation samples
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In this paper, the results of an investigation into electrical tree growth in XLPE cable insulation using an embedded needle electrode are reported for a range of voltages from 9 kV rms to 27 kv rms.Abstract:
The results of an investigation into electrical tree growth in XLPE cable insulation using an embedded needle electrode are reported for a range of voltages from 9 kV rms to 27 kV rms. The partial discharge (PD) activity and tree structures were measured simultaneously throughout the tree growth and the trees were recorded from initiation up to and including the final runaway stage. A multifractal analysis was also performed on the tree structures as they propagated, and it was found that their fractal dimension increased and the distribution of embedded structures changed as small side channels were added to the tree as it grew. At 11 kV rms only branch trees were found and only bush (bush-branch) trees at higher voltages, but at 9 kV rms trees of three different shapes were formed. Observation of the tree shapes at 9 kV rms under reflected light followed by a detailed analysis using con-focal Raman spectroscopy, showed that the stagnated and branch-pine (monkey puzzle) tree shapes were due to the formation of a conducting graphitic deposit upon the walls on tree branches in the region of the needle electrode. This was not present in the branch trees produced at 9 kV rms. A simple scheme is presented for the formation of branch-pine trees and their corresponding PD activity based on the concept of conducting branch generation. The trees produced at 13 kV rms and above have a bush shape, which converts into a bush branch shape when a runaway branch grows from their periphery. This is shown to happen when the field at the bush tree periphery exceeded a voltage independent critical value, which was estimated to be 100 MV/m. The consequence of this result for the initiation of the runaway stage in branch trees is commented upon.read more
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Journal ArticleDOI
Electrical tree initiation in XLPE cable insulation by application of DC and impulse voltage
Liu Ying,Cao Xiaolong +1 more
TL;DR: In this paper, the initiation behavior of XLPE cable insulation was investigated by application of DC voltage, impulse voltage, repetitive DC voltage and impulse voltage after DC prestressing, and no trees appeared when DC voltage up to 70 kV or -60 kV was applied on the samples continuously or repetitively.
Journal ArticleDOI
Imaging and analysis techniques for electrical trees using X-ray computed tomography
TL;DR: In this paper, the authors present the application of X-ray computed tomography (XCT) for electrical tree imaging, which is able to reveal electrical trees, providing a threedimensional (3D) view and therefore, a more complete representation of the phenomenon can be achieved.
Journal ArticleDOI
Electrical treeing behavior at high temperature in XLPE cable insulation samples
TL;DR: In this paper, the behavior of electrical trees formed in XLPE cable insulation at elevated temperatures was investigated, and it was found that temperature and voltage level had a pronounced effect on the process of electrical tree formation.
Journal ArticleDOI
DC electrical tree growth in epoxy resin and the influence of the size of inceptive AC trees
TL;DR: In this paper, the authors examined the importance of polarity and defect size on electrical tree propagation in epoxy resin under constant DC voltages of + 60 kV and −60 kV, but with small initial trees (< 100 μm) incepted under lower AC voltages before the DC tests.
Journal ArticleDOI
Insulating materials for realising carbon neutrality: Opportunities, remaining issues and challenges
Chuanyang Li,Yang Yang,Guoqiang Xu,Yao Zhou,Mengshuo Jia,Shao Long Zhong,Yu Gao,Chan-Myun Park,Qiang Liu,Yalin Wang,Shakeel Akram,Xiaoliang Zeng,Yi Li,Fangwei Liang,Binhang Cui,Junpeng Fang,Lingling Tang,Yulin Zeng,Xingtao Hu,Jiachen Gao,Giovanni Mazzanti,Jinliang He,Jianxiao Wang,D. Fabiani,Gilbert Teyssedre,Yang Cao,Feipeng Wang,Yunlong Zi +27 more
TL;DR: In this article , the authors discuss the challenges regarding design and reliability of insulations in electrical equipment and electric vehicles in the context of policies towards carbon neutrality rules, and also hope that this paper can be helpful in future development and research of novel insulating materials, which promote the realisation of the carbon-neutral vision.
References
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Book
Electrical degradation and breakdown in polymers
L.A. Dissado,John C. Fothergill +1 more
TL;DR: In this paper, the physical and chemical structure of polymers and their breakdown are discussed, along with the stochastic nature of break-down from empirical and modelling viewpoints, and practical implications and strategies for engineers.
Journal ArticleDOI
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TL;DR: In this article, it was shown that there is an infinity of generalized dimensions for strange attractors, related to the order-q Renyi entropies, and that these dimensions are monotonically decreasing with q.
Journal ArticleDOI
Understanding electrical trees in solids: from experiment to theory
TL;DR: A review of recent developments made in the understanding of the electrical tree mechanism is presented and the chaotic nature of the tree propagation mechanism is discussed both through experimental data and the results of a completely deterministic theoretical model.
Journal ArticleDOI
Breakdown of Solid Dielectrics in Divergent Fields
TL;DR: In this article, the average breakdown stress of steel needle-point electrodes embedded in polythene and polyisobutylene polycarbonate polycarbonates was investigated and the effect of enhanced conductivity and space charge accumulation increasing the effective point radius to some 25 and 45 microns for positive and negative points.
Journal ArticleDOI
An Investigation into the Growth of Electrical Trees in XLPE Cable Insulation
TL;DR: In this paper, the effects of frequency, voltage, temperature and mechanical stress on the times to breakdown of XLPE cable insulation subjected to highly divergent fields were investigated and it was shown that space charges are dominant in determining the shape of the tree and the time to breakdown.
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