Model for partial discharges associated with treeing breakdown: III. PD extinction and re-growth of tree

Wu, Kai; Suzuoki, Yasuo; Mizutani, Teruyoshi; Xie, Hui

doi:10.1088/0022-3727/33/10/312

Cited by 44 publications

(23 citation statements)

References 11 publications

(23 reference statements)

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“…Both S Kþ and S KÀ exhibit a negative trend with ageing. The effect of conductivity in the channels has been proposed to be responsible for similar changes observed and modelled for trees in ethylene-acrylic acid copolymer (EAA) [28,48,49]. Similar to these observations, a decrease in partial discharge activity ( Figure 4) and tree growth rate is observed after the transition from the branched to the bush-type structure.…”

Section: Temporal Evolution and Retardation Of Tree Propagationsupporting

confidence: 65%

“…However, it must be mentioned that the measured and modelled conductivities lie between 10 À16 (V Á cm) À1 and 10 À10 (V Á cm) À1 . According to the model on partial discharge extinction proposed by Wu et al [49], the increase in conductivity in the tips of the channels is responsible for the retardation of channel propagation. At this point, the mica barrier introduced in the samples comes into play.…”

Section: Temporal Evolution and Retardation Of Tree Propagationmentioning

confidence: 99%

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Retardation of electrical tree propagation by resin degradation

Weiers¹,

Keller²,

Hutter

et al. 2006

Int Trans Elec Energy Syst

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SUMMARYIn order to improve insight into the effect of delaminations between the conductor and the groundwall insulation on the ageing of high voltage rotating machinery insulation, the influence of the polymer degradation on tree growth has been studied. Simultaneous partial discharge measurements and photograhic observations have been conducted in order to investigate the effect of the degradation of the resin on electrical tree propagation. The photographic observation indicates that the degradation of the resin retards the tree propagation after the tree having failed to penetrate a mica barrier. As the resin is degraded and in part rendered conducting, the partial discharges change both in magnitude and in terms of phase resolved partial discharge patterns. These partial discharge measurements are promising to improve insight into the processes involved in winding insulation ageing, when photographic observations are unattainable. Moreover the differences found between various resins offer an explanation why various types of winding insulation have been found to differ in their capability to withstand thermal cyclic ageing.

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Section: Temporal Evolution and Retardation Of Tree Propagationsupporting

confidence: 65%

Section: Temporal Evolution and Retardation Of Tree Propagationmentioning

confidence: 99%

Retardation of electrical tree propagation by resin degradation

Weiers¹,

Keller²,

Hutter

et al. 2006

Int Trans Elec Energy Syst

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“…There are two reasons for the appearance of pine-branch tree, one is the tiny breakdown of the material at the tip of needle, which is proved by the black color of the tree implying the conducting tunnel of the tree; the other reason is that the residual stress makes the material in this region more easily to break down. In addition, the growth characteristics of two-part structure trees generated under residual stress are similar to those generated trees after PD [27].…”

Section: The Electrical Trees With Residual Stress At Low Frequencymentioning

confidence: 59%

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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“…Electrical treeing is one of the main failure mechanisms in high voltage (HV) polyethylene cable insulation, where dendritic paths progressively grow from high stress regions and branch into hollow channels in a solid dielectric [1][2][3][4]. Once the tree initiates in cable insulation, it starts to grow through the insulation and finally leads to the failure of the cable.…”

Section: Introductionmentioning

confidence: 99%

Effect of morphology on electrical treeing in low density polyethylene nanocomposites

Alapati

Meledath

Karmarkar

2014

IET Science, Measurement & Technology

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Influence of polymer morphology on the inception and the growth of electrical trees in unfilled low density polyethylene (LDPE) as well as LDPE filled with 1, 3 and 5% by weight nanoalumina samples stressed with 50 Hz ac voltage has been studied. It is seen that there is a significant improvement in tree inception voltage with filler loading in LDPE filled with nanoparticles. Tree inception voltage increased with the filler loading up to 3% by weight nanoalumina loading and showed a reduction at 5% by weight loading. Change in tree growth patterns from branch to bush as well as a slower tree growth with increase in filler loading in LDPE alumina nanocomposites were observed. The degree of crystallinity and change in crystalline morphology induced by the presence of alumina nanoparticles in LDPE was studied using differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). DSC results show a similar melting behaviour for both unfilled LDPE and LDPE nanocomposites. However, there is a reduction in the degree of crystallinity for LDPE filled with 5% by weight nanoalumina. An increase in lamellae packing with increase in filler loadings and a highly disordered spherulitic structure for LDPE filled with 5% by weight nanoalumina was observed from the SEM images. The slow propagation of tree growth as well as reduction in tree inception voltage with increase in filler loadings were attributed to the morphological changes observed in the LDPE nanocomposites.

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Model for partial discharges associated with treeing breakdown: III. PD extinction and re-growth of tree

Cited by 44 publications

References 11 publications

Retardation of electrical tree propagation by resin degradation

Retardation of electrical tree propagation by resin degradation

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

Effect of morphology on electrical treeing in low density polyethylene nanocomposites

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