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Periodic grounded dc trees in cross-linked polyethylene under various dc prestressing times are investigated in the temperature range of 20 °C–80 °C. Space charge behaviors in the samples during dc prestressing are simulated based on the bipolar charge transport model. The results reveal that the dc prestressing time has different effects on the tree growth at different temperatures, which is because...
Electrical tree break-down is the major failure problem in cable accessories, however, mechanisms of the electrical tree initiation and propagation are still lack of deeply research, especially in silicone rubber (SIR) which is widely used as insulation material for cable accessories. Long-term aging (0– 1000 h) experiments under the different voltages were conducted to observe electrical tree initiation...
Cross-linked polyethylene(XLPE) is widely used as the insulation of power cables due to its good properties. Nevertheless, some inevitable defects like cracks and cavities existing in cables will initiate electrical trees which is one of the main reason leading to the breakdown of cable insulation. Thus, it is necessary to conduct the study on the effects of cavity on the growth of electrical trees...
Most of the high voltage (HV) power equipment is made up with solid insulation like paper insulation, glass insulation, epoxy insulation etc. The oldest kind of insulating material among all insulation, the paper insulation is used in cable and nowadays the Cross linked Polyethylene (XLPE) is commonly used for cable insulation. The presence of impurities in the insulation system is one of the root...
Experimental investigations on treeing breakdown characteristics of cross-Linked polyethylene (XLPE) cables immersed in transformer oil are introduced and discussed in this paper. The study has been done under alternating (50 Hz) and direct voltage stresses. Thereby, the effect of duration, waveform and polarity of the applied voltage as well as the temperature rise of oil, the size of cable and the...
Water treeing is the main inducement of insulating breakdown of polyethylene power cables which are used in humid environment. Water tree may initiate electrical tree, which can eventually cause insulation breakdown of power cables. In order to study the inception and propagation mechanisms of electrical tree transformed from water tree, and to evaluate the degradation degree of water tree, it is...
In this paper, room temperature vulcanized (RTV) silicone rubber (SiR) was employed as test sample to investigate the relationship between electrical tree propagation characteristics and the experiment temperature. Both the structures and growth characteristics of electrical tree in SiR were observed by using a digital camera and a microscope system. Obtained results show that electrical tree in RTV...
In order to clarify the mechanism of electrical-tree inception from water-tree degradation which often determines the remaining life of power cables, we have been investigating electrical tree inception and propagation from water-tree degradation in polyethylene. Some of the results suggested that at higher temperatures the extent of water-tree degradation was much higher than that of water-tree degradation...
In order to clarify the mechanism of electrical-tree inception and propagation from a water tree within polyethylene, we have investigated temperature dependence of water tree and electrical tree inception and propagation from water-tree degradation. In the samples with water tree of the area above ca. 5000 mum2, the ac electrical-tree inception voltage increased with increasing water-tree degradation...
The authors have examined the effects of superposition of a low-frequency ac voltage and a high-frequency ac voltage on the growth of water trees in polyethylene, and have made it clear that the number of voltage zero-crossings is a decisive factor of water tree growth. In the present research, a short-duration high-frequency (2 kHz) voltage was superposed repeatedly onto a continuously applied low-frequency...
The courageous acceptance of cross-linked polyethylene (XLPE) cables for power transmission and distribution during the past decade results from significant advances in manufacturing technology and quality. Successful service stimulates cable engineers to extend XLPE cable toward higher power capability through higher operating voltages. In recent years two practical and technological approaches have...
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