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Investigations of Electrical Trees in the Inner Layer of XLPE Cable Insulation Using Computer-aided Image Recording Monitoring

Investigations of Electrical Trees in the Inner Layer of XLPE Cable Insulation Using Computer-aided Image Recording Monitoring
Investigations of Electrical Trees in the Inner Layer of XLPE Cable Insulation Using Computer-aided Image Recording Monitoring
Using a computer-aided image recording monitoring system, extensive measurements have been performed in the inner layer of 66 kV cross-linked polyethylene (XLPE)cables. It has been found that there are three kinds of electrical trees in the samples,the branch-like tree, the bush-like tree and the mixed tree that is a mixture of the above two kinds. When the applied voltage frequency is less than or equal to 250 Hz, only the mixed tree appears in XLPE samples, when the frequency is greater than or equal to 500 Hz, only the dense branch-like tree develops, both of which are attributed to the coexistence of non-uniform crystallization and internal residual stress in semicrystalline XLPE cables during the process of manufacturing. Through the fractal analyses of these electrical trees, it has been found that both the propagation and structure characteristics can be described by fractal dimension directly or indirectly. It is suggested that the propagation and structural characteristics of electrical trees are closely related to the morphology and the residual stress in material at low frequency, i.e., the propagation characteristics of electrical trees depends upon not only the boundaries between big spherulites and amorphous region, but also the impurity, micropore concentration and the relative position of needle electrode tip with respect to spherulites or amorphous region in the low frequency range. However, at high frequency, it has nothing to do with the morphology of material. It is suggested that the injection and extraction process of charge from and to dielectrics via the needle electrode are more intense at high frequency than in low frequency. Thus, it can form relatively uniform dielectric weak region in front of needle electrode, which leads to similar initiation and propagation characteristics of electrical trees at high frequency.
Cross-linked polyethylene cable insulation, electrical trees, frequency, residual stress, morphology
1070-9878
685-693
Xie, Ansheng
3b0df7b4-f157-424f-9f06-6e43be1a7a1f
Zheng, Xiaoquan
88349f57-8c82-439e-bdf6-6b59a14309af
Li, Shengtao
e2d199c9-1c0c-40c8-aefb-ff3b3d8e4799
Chen, George
3de45a9c-6c9a-4bcb-90c3-d7e26be21819
Xie, Ansheng
3b0df7b4-f157-424f-9f06-6e43be1a7a1f
Zheng, Xiaoquan
88349f57-8c82-439e-bdf6-6b59a14309af
Li, Shengtao
e2d199c9-1c0c-40c8-aefb-ff3b3d8e4799
Chen, George
3de45a9c-6c9a-4bcb-90c3-d7e26be21819

Xie, Ansheng, Zheng, Xiaoquan, Li, Shengtao and Chen, George (2010) Investigations of Electrical Trees in the Inner Layer of XLPE Cable Insulation Using Computer-aided Image Recording Monitoring. IEEE Transactions on Dielectrics & Electrical Insulation, 17 (3), 685-693.

Record type: Article

Abstract

Using a computer-aided image recording monitoring system, extensive measurements have been performed in the inner layer of 66 kV cross-linked polyethylene (XLPE)cables. It has been found that there are three kinds of electrical trees in the samples,the branch-like tree, the bush-like tree and the mixed tree that is a mixture of the above two kinds. When the applied voltage frequency is less than or equal to 250 Hz, only the mixed tree appears in XLPE samples, when the frequency is greater than or equal to 500 Hz, only the dense branch-like tree develops, both of which are attributed to the coexistence of non-uniform crystallization and internal residual stress in semicrystalline XLPE cables during the process of manufacturing. Through the fractal analyses of these electrical trees, it has been found that both the propagation and structure characteristics can be described by fractal dimension directly or indirectly. It is suggested that the propagation and structural characteristics of electrical trees are closely related to the morphology and the residual stress in material at low frequency, i.e., the propagation characteristics of electrical trees depends upon not only the boundaries between big spherulites and amorphous region, but also the impurity, micropore concentration and the relative position of needle electrode tip with respect to spherulites or amorphous region in the low frequency range. However, at high frequency, it has nothing to do with the morphology of material. It is suggested that the injection and extraction process of charge from and to dielectrics via the needle electrode are more intense at high frequency than in low frequency. Thus, it can form relatively uniform dielectric weak region in front of needle electrode, which leads to similar initiation and propagation characteristics of electrical trees at high frequency.

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Published date: June 2010
Keywords: Cross-linked polyethylene cable insulation, electrical trees, frequency, residual stress, morphology
Organisations: Electronics & Computer Science, EEE

Identifiers

Local EPrints ID: 271314
URI: http://eprints.soton.ac.uk/id/eprint/271314
ISSN: 1070-9878
PURE UUID: b04c2d79-080e-4d71-ac30-e3d9bb11a826

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Date deposited: 28 Jun 2010 16:15
Last modified: 09 Dec 2019 20:10

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