Yang Xu

TL;DR: In this paper, the results of an investigation into electrical tree growth in XLPE cable insulation using an embedded needle electrode are reported for a range of voltages from 9 kV rms to 27 kv rms.

TL;DR: In this paper, the authors focused on the oxidation stability assessment of a vegetable transformer oil under accelerated thermal aging at 110°C with various durations up to 2500 hours, and showed that viscosity responds more than acidity to oxidation more than hydrolysis whereas acidity responds strongly to both oxidation and acidity also generates acid byproducts.

TL;DR: In this paper, the behavior of electrical trees formed in XLPE cable insulation at elevated temperatures was investigated, and it was found that temperature and voltage level had a pronounced effect on the process of electrical tree formation.

TL;DR: In this article, the authors investigated the nonlinear dynamics characteristics of the partial discharge (PD) sequence measured during the propagation of typical electrical trees in XLPE cable insulation and provided strong evidence for the existence of deterministic chaos in the PD phenomenon of electrical trees.

Abstract: 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, Tγ, 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