Effect of tree channel conductivity on electrical tree shape and breakdown in XLPE cable insulation samples

“…At the beginning, the tree forms a branch structure rapidly. When a conducting region around the needle electrode resulting in a short-circuiting is formed, charges in this region are prevented to reach the tip, leading to the stagnation of main branches [42]. If this conducting region is not formed, the tree structure will be a branch-pine tree.…”

Section: Tree Structure Distributionmentioning

confidence: 99%

“…The electric field is intensified when the tip of tree channel is close to the ground electrode. When the electric field is strong enough, a pine structure is generated at the tip of the main branch, which means the formation of a branch-pine tree [42]. When temperature is 30, -30 or -90 °C, oxygen is in the status of gas, but when it decreases to -196 °C, oxygen is liquefied [38], in which status the oxygen is rather difficult to react with carbonized products.…”

Section: Tree Structure Distributionmentioning

confidence: 99%

Electrical tree characteristics of XLPE under repetitive pulse voltage in low temperature

Zhu

2015

IEEE Trans. Dielect. Electr. Insul.

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Cross-linked polyethylene (XLPE) may be operated under repetitive pulse voltage and low temperature environment. In recent years, many influencing factors to the treeing process, which is a main reason for the aging of XLPE have been researched. However, the tree behavior under repetitive pulse voltage and low temperature in XLPE is still not clear. In this paper, the tree behavior under repetitive pulse voltage and low temperature was investigated and analyzed. A positive pulse voltage with the amplitude of 12 kV and the frequency of 300 and 400 Hz was applied on the needle-plate electrodes. The experimental temperature was set to 30, -30, -90 and -196 °C. Four typical morphologies of the electrical trees are observed, including bush, branch, branch-pine and stagnated tree. It is revealed that low temperature has an obvious effect on tree structures and it can reduce the tree growth rate and extend the time to breakdown. It is also revealed that the tree inception probability becomes lower with the decrease of temperature. With the increase of pulse frequency, the tree growth rate, the fractal dimension and the number of tree channels increases and the tree inception probability becomes higher, but the morphologies of electrical trees stay the same.Index Terms -XLPE, repetitive pulse voltage, low temperature, electrical tree, tree inception, tree length, fractal dimension, dielectric breakdown.

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“…Figure 1 shows a schematic diagram of sample and electrodes. Sample preparations have been described previously in reference [25]. The experimental circuit consisted of variable autotransformer, a step-up transformer with power frequency of 50 Hz, a protection resistor; a capacitive voltage divider; and a 2000 pF coupling capacitor.…”

Section: Electrical Tree Experimentsmentioning

confidence: 99%

Investigation on insulation material morphological structure of 110 and 220 kV XLPE retired cables for reusing

Yang

Luo

et al. 2014

IEEE Trans. Dielect. Electr. Insul.

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Most of the 110 and 220 kV cables are in service till the end of life, but part of them would be out of service by refurbishment. This research is focused on evaluating the cable insulation and determining whether the cable can be reused. All the cables used in this research satisfactorily passed the AC voltage and partial discharge tests. Then the fourier transform infrared spectroscopy, thermogravimetry analysis, differential scanning calorimetry, dynamic mechanical analysis, and tensile machine were used to analyze the insulation morphological structure and performance of 20 retired 110 and 220 kV crosslinked polyethylene cables obtained from the Beijing and Zhuhai districts. The results show that the structure parameters which can represent the physical change and the irreversible chemical change of cables have obvious time dependence characteristic. DSC result shows that crystallinity, melting range, and crystallization rate increase slightly with service years. DMA experiment illustrates that the temperature of mechanical loss peak, T γ , shifts to a higher temperature while the mechanical loss increases slightly and temperature dependency of storage modulus increases with service years. The electrical treeing experiment utilized cable operated for 17 years, which is the longest operation year for the samples. Compared with new cable, the cable operated for 17 years has a slight decrease in tree initiation time and an obvious increase in tree propagation time. These experiment data show that the insulation material morphological structure is mainly stable, and the test results are also a contribution to the lifetime expectancy evaluation of the 110 and 220 kV XLPE cable.

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Effect of tree channel conductivity on electrical tree shape and breakdown in XLPE cable insulation samples

Cited by 137 publications

References 30 publications

Self-healing during electrical treeing: A feature of the two-phase liquid-solid nature of silicone gels

Self-healing during electrical treeing: A feature of the two-phase liquid-solid nature of silicone gels

Electrical tree characteristics of XLPE under repetitive pulse voltage in low temperature

Investigation on insulation material morphological structure of 110 and 220 kV XLPE retired cables for reusing

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