An Investigation into the Growth of Electrical Trees in XLPE Cable Insulation

Densley, R.J.

doi:10.1109/tei.1979.298215

Cited by 149 publications

(57 citation statements)

References 11 publications

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“…The fine tree channels may then be generated by crack propagation caused by released electrostatic energy and electromechanical strain energy stored in the material [14] which subsequently supports high discharge activity when dark tree channels develop. The dark and wide tree channels, observed from 250 to 450 Hz as shown in Figure 3, may be caused by erosion of tree channels due to rapid charge injection and extraction every half cycle of the applied voltage frequency [5]. This is a primary reason for accelerated ageing at higher frequencies.…”

Section: Frequency-dependent Tree Growth and Time To Breakdownmentioning

confidence: 99%

“…Investigation of cables removed from service shows that treeing degradation is an important physical indication of internal damage to cable insulation, typically emanating from points of high electrical stress or defects in the insulation system [2]. Tree initiation, propagation rate, structure and time to breakdown is influenced by the magnitude of the applied voltage, the frequency of the test voltage, as well as the local electric field in the material [3][4][5][6]. Tree channel expansion and extension is linked to partial discharges in the tree channel column and is frequency dependent [3].…”

Section: Introductionmentioning

confidence: 99%

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The impact of harmonic frequencies on electrical tree growth in epoxy resin

Iddrissu

Rowland

2017

2017 IEEE Conference on Electrical Insulation and Dielectric Phenomenon (CEIDP)

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Abstract-Electrical treeing in solid polymeric insulation is physical evidence of internal damage and ultimately leads to equipment failure. This study considers the effect of frequency on treeing breakdown times in epoxy resin between 50 Hz to 450 Hz. The tree structures generated from 50 to ~250 Hz were filamentary, had narrow channels and spread throughout the insulation. Tree structures generated from ~250 Hz to 450 Hz were darker, having wider channels and less branching. The rate of tree initiation and propagation increases with increasing frequency, resulting in reduced time to breakdown. This has implications that harmonics in AC and DC networks require careful management to ensure insulation reliability is not compromised.

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Section: Frequency-dependent Tree Growth and Time To Breakdownmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The impact of harmonic frequencies on electrical tree growth in epoxy resin

Iddrissu

Rowland

2017

2017 IEEE Conference on Electrical Insulation and Dielectric Phenomenon (CEIDP)

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“…In underground cables, under normal operating voltage, the partial discharges incepts pre-breakdown channels from a region of defect site present in the form of gas cavities or conducting inclusions or intrusions, in the insulation structure, due to field enhancement. These pre-breakdown channels emanated from the defect site in the insulation structure resemble branches of a tree and, hence, the name "treeing" is given to the damage process and since such an occurrence is purely due to electrical stress the mechanism is termed as "Electrical Treeing" [2][3][4][5]. In general, the partial discharge injected current pulses involve rise and fall-times of about 1 ns or less, exciting signals in the UHF range of 300-3000 MHz [6].…”

Section: Introductionmentioning

confidence: 99%

Understanding Electrical Treeing Phenomena in XLPE Cable Insulation Adopting UHF Technique

Sarathi¹,

Nandini²,

Danikas³

2011

Journal of Electrical Engineering

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A major cause for failure of underground cables is due to formation of electrical trees in the cable insulation. A variety of tree structure can form from a defect site in cable insulation viz bush-type trees, tree-like trees, fibrillar type trees, intrinsic type, depending on the applied voltage. Weibull studies indicate that a higher applied voltage enhances the rate of tree propagation thereby reducing the life of cable insulation. Measurements of injected current during tree propagation indicates that the rise time and fall time of the signal is of few nano seconds. In the present study, an attempt has been made to identify the partial discharges caused due to inception and propagation of electrical trees adopting UHF technique. It is realized that UHF signal generated during tree growth have signal bandwidth in the range of 0.5-2.0 GHz. The formation of streamer type discharge and Townsend type discharges during tree inception and propagation alters the shape of the tree formed. The UHF signal generated due to partial discharges formed during tree growth were analyzed adopting Ternary plot, which can allow one to classify the shape of tree structure formed.

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“…It therefore brings up a new subject to the study of electrical trees. Many papers have studied the effects of morphology of semi-crystalline material on the initiation and propagation of electrical trees in the past decades [5,6,9,10], but little attention was paid to the influence of frequency and residual stress on electrical tree in XLPE cable insulation, only the papers concerning the effect of frequency up to 800 Hz have been reported [7,11]. In this paper, the initiation, propagation and the structural characteristics of electrical trees under sinusoidal wave high voltage of 50 2000 Hz in XLPE cable insulation are studied systematically.…”

Section: Introductionmentioning

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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An Investigation into the Growth of Electrical Trees in XLPE Cable Insulation

Cited by 149 publications

References 11 publications

The impact of harmonic frequencies on electrical tree growth in epoxy resin

The impact of harmonic frequencies on electrical tree growth in epoxy resin

Understanding Electrical Treeing Phenomena in XLPE Cable Insulation Adopting UHF Technique

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

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