Insulation morphology effects on the electrical treeing resistance

Harlin, Ali; Shuvalov, M. Yu.; Ovsienko, V. L.; Juhanoja, Jyrki

doi:10.1109/tdei.2002.1007703

Cited by 10 publications

(7 citation statements)

References 6 publications

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“…Multiple studies of various types of PE for medium and high voltage cables insulations have highlighted the dependence of the electric tree rate development on various factors, such as intensity of the electric field [194], the electric field frequency [193,195,196], chemical characteristics [197] and physical structure of the polymer [198,199,200,201,202], temperature [194], impurities concentration [203], moisture content [204], mechanical stress [155,156,205,206,207], as well as electrodes characteristics, shapes and dimensions [208,209]. Several new PE compounds containing organic additives (such as polycyclic aromatic compounds or benzophenone derivatives) [203] were obtained, which can capture high-energy electrons and dissipate their energy [210] while forming aromatic anions [42].…”

Section: Electrical Treeing In Nanocompositesmentioning

confidence: 99%

Polyethylene Nanocomposites for Power Cable Insulations

et al. 2018

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This review represents a comprehensive study of nanocomposites for power cables insulations based on thermoplastic polymers such as polyethylene congeners like LDPE, HDPE and XLPE, which is complemented by original results. Particular focus lies on the structure-property relationships of nanocomposites and the materials’ design with the corresponding electrical properties. The critical factors, which contribute to the degradation or improvement of the electrical performance of such cable insulations, are discussed in detail; in particular, properties such as electrical conductivity, relative permittivity, dielectric losses, partial discharges, space charge, electrical and water tree resistance behavior and electric breakdown of such nanocomposites based on thermoplastic polymers are described and referred to the composites’ structures. This review is motivated by the fact that the development of polymer nanocomposites for power cables insulation is based on understanding more closely the aging mechanisms and the behavior of nanocomposites under operating stresses.

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Section: Electrical Treeing In Nanocompositesmentioning

confidence: 99%

Polyethylene Nanocomposites for Power Cable Insulations

et al. 2018

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“…The observing cross-section of the samples was obtained by brittle rupturing the sample placed inside liquid nitrogen at the temperature of 190 o C, then sprayed gold electrodes, and then the morphology of cross-section of the samples was obtained with the SEM. It is fond that the size of the spherulites is generally among 1 10 m. As it is showed in literature [24,25], the resistance to electrical trees in XLPE cable insulation is worse than PE because of the imperfect crystallization and the formation of large spherulites of XLPE due to crystal nucleus destroyed by cross linking. Literature [26] has studied the crystalline morphology of the 35 kV XLPE cable insulation by Freeze-rupture and potassium permanganate etching method and found that the diameters of the equivalent spherulites in the cable insulation were typically between 4 40 m or greater.…”

Section: The Electrical Trees At Low Frequency and The Non-uniform Crmentioning

confidence: 99%

“…For instance, when the material is crystallized at 124 ºC, it is observed that 12 percent of electric trees are located at the surface layer of the spherulites, 20 percent occurs in the region with low crystalline and 68% are related to the boundary of the spherulites. As it is showed in literature [24,25] that the electrical trees of XLPE cable insulation were easier for growth along the large spherulites surface because of the imperfect crystallization and the existence of large spherulites in XLPE. As pointed out by Toshikatsu Tanaka [10], the weak region is composed of the delamination and three-dimensional network among spherulites.…”

Section: The Electrical Trees With Residual Stress At Low Frequencymentioning

confidence: 99%

Investigations of electrical trees in the inner layer of XLPE cable insulation using computer-aided image recording monitoring

Xie

Zheng

2010

IEEE Trans. Dielect. Electr. Insul.

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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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“…The higher amplitude PD pulses are correlated with the PD activity occurring from the pin tip into the tree channels whereas the lower magnitude discharges are correlated with the localized discharges occurring at the isolated points in the tree structure and at the growing tree tips. Harlin et al [17] studied the propagation characteristics of electrical trees in 220 kV XLPE cables insulation and suggested that insulation morphology has a great influence on the initiation voltage, while its effects on propagation and statistical characteristics of electrical trees for different high voltage rating XLPE cables insulation have not been considered yet. In our previous papers, the propagation characteristics of electrical trees in both the inner and the outer layers of the 66 kV XLPE cable insulation [21,22] have been compared, which indicates that the morphology, the structure and the growth characteristics of electrical trees are very different between the inner and the outer regions of the XLPE cable insulation.…”

Section: Introductionmentioning

confidence: 99%

The characteristics of electrical trees in the inner and outer layers of different voltage rating XLPE cable insulation

Xie¹,

Zheng²

2009

J. Phys. D: Appl. Phys.

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The statistical initiation and propagation characteristics of electrical trees in cross-linked polyethylene (XLPE) cables with different voltage ratings from 66 to 500 kV were investigated under a constant test voltage of 50 Hz/7 kV (the 66 kV rating cable is from UK, the others from China). It was found that the characteristics of electrical trees in the inner region of 66 kV cable insulation differed considerably from those in the outer region under the same test conditions; however, no significant differences appeared in the 110 kV rating cable and above . The initiation time of electrical trees in both the inner and the outer regions of the 66 kV cable is much shorter than that in higher voltage rating cables; in addition the growth rate of electrical trees in the 66 kV cable is much larger than that in the higher voltage rating cables. By using x-ray diffraction, differential scanning calorimetry and thermogravimetry methods, it was revealed that besides the extrusion process, the molecular weight of base polymer material and its distribution are the prime factors deciding the crystallization state. The crystallization state and the impurity content are responsible for the resistance to electrical trees. Furthermore, it was proposed that big spherulites will cooperate with high impurity content in enhancing the initiation and growth processes of electrical trees via the 'synergetic effect'. Finally, dense and small spherulites, high crystallinity, high purity level of base polymer material and super-clean production processes are desirable for higher voltage rating cables.

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Insulation morphology effects on the electrical treeing resistance

Cited by 10 publications

References 6 publications

Polyethylene Nanocomposites for Power Cable Insulations

Polyethylene Nanocomposites for Power Cable Insulations

Investigations of electrical trees in the inner layer of XLPE cable insulation using computer-aided image recording monitoring

The characteristics of electrical trees in the inner and outer layers of different voltage rating XLPE cable insulation

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