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1.
Laboratory tests were performed to investigate the effects of lightning and thumping impulses on the performance of various 15 kV cable designs. The cable designs were aged in the laboratory using an accelerated water treeing test. Some samples were subjected to lightning impulses, some were subjected to thumping impulses, and some were aged without impulses applied. The impulse effects were evaluated using time to failure data, AC breakdown data, and impulse breakdown data. The results show that lightning or thumping impulses do not affect cable AC or impulse breakdown strength. There is also no visual difference between wafers taken from impulsed and control samples. However, there is a strong indication that lightning impulses can reduce cable life. Almost all the aging failures occurred while the cables were warm. No failures occurred during the impulse application. It is also shown that increased cable wall thickness extends cable life for the tree-resistant high-molecular-weight insulation material tested, but not for the crosslinked polyethylene insulation material tested 相似文献
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硫化工艺对抗水树交联聚乙烯绝缘电力电缆工频击穿性能的影响 总被引:1,自引:0,他引:1
为了研究不同硫化工艺对抗水树枝交联聚乙烯绝缘电缆击穿性能的影响,建立了相应的试验手段和评价程序。将使用相同导体屏蔽料、抗水树绝缘料、绝缘屏蔽料,并采用5种不同硫化工艺(A、B、C、D、E)生产的电压等级、型号规格相同且结构相似的电缆作为研究对象,每种电缆取6段作样品,共30段。分别对老化前和老化180d后的5种样品进行工频击穿试验,并观察击穿后样品切片的水树枝、界面微孔、突起和绝缘中的微孔、杂质。试验结果表明:经过180d的加速老化后,5种样品中均无微孔、界面光滑、有少量尺寸较小的杂质,不会导致击穿性能下降;不同硫化工艺生产的电缆工频击穿性能表现出明显差异,其中,A硫化工艺生产的电缆工频击穿强度下降了53.53%,击穿后的样品中观察到了水树枝,B、C硫化工艺生产的电缆工频击穿强度也有不同程度的下降,而D、E硫化工艺生产的电缆的工频击穿强度没有降低,说明硫化工艺对工频击穿强度有直接的影响,并建议实际生产中确定硫化工艺时,各区温度设定应逐渐降低,且初始硫化温度不应过低,生产线速度应适当。 相似文献
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《Power Delivery, IEEE Transactions on》2004,19(4):1532-1537
This paper provides data on four commercial tree retardant crosslinked polyethylene (TR-XLPE) and one cross-linked polyethylene (XLPE) insulated 15 kV cables supplied by three manufacturers. The cables have "super-smooth" conductor shields and "extra-clean" insulation and insulation shields. AC and impulse voltage breakdown and selected other characterization data are presented for cables that were aged immersed in room temperature water (15-30/spl deg/C) up to 24 months of a planned 48 months aging program. The five cables have high ac voltage breakdown strength, three of the TR-XLPE cables, actually increased in breakdown strength during aging. The one TR-XLPE cable that had the lowest ac voltage breakdown had vented trees at the insulation shield and high dissipation factor, which the other cables did not have. The impulse voltage breakdown strength of all cables decreased during aging; the cable with the lowest ac voltage breakdown also has the lowest impulse voltage breakdown. The dissimilar performance of the TR-XLPE cables and the excellent performance of the XLPE cable indicates evaluations at longer times are required to differentiate between modern TR-XLPE and XLPE insulated cables. 相似文献
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500kV XLPE电缆绝缘中树枝化现象的述评 总被引:4,自引:0,他引:4
介绍日本开发 5 0 0 k V XL PE电力电缆时研究树枝化现象的形成 ,评述 XL PE电缆形成电树和水树与场强的相关性、树枝引发场强和长期寿命特性的研究结果 ,说明由此确定 5 0 0 k V XL PE电力电缆的绝缘设计。 相似文献
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TAKASHI KURIHARA EIJI TSUTSUI EIJI NAKANISHI KIYOSHI MAKI KENICHI MURAKAWA KOJI MORIMOTO TOSHIHIRO TAKAHASHI TATSUKI OKAMOTO 《Electrical Engineering in Japan》2017,198(4):37-50
Dry‐cured and extruded three‐layer (E‐E type) 6.6‐kV cross‐linked polyethylene (XLPE) cables were introduced into electric power systems more than 30 years ago, but they do not experience failures because of water tree degradation. Also, the degradation index of water treeing for these cables has not been established. Therefore, investigating results of residual breakdown voltage and water tree degradation of these cables will help us plan for cable replacement and determine water tree degradation diagnosis scheduling, and will be fundamental data for cable lifetime evaluation. In this study, the authors measured the ac breakdown voltages of dry‐cured and E‐E type 6.6‐kV XLPE cables removed after 18 to 25 years of operation and observed the water trees in their XLPE insulation. As a result, it was observed that breakdown voltages were larger than the maximum operating voltage (6.9 kV) and the ac voltage for the dielectric withstanding test (10.3 kV). Water trees were mainly bow‐tie water trees and their maximum length was approximately 1 mm. Although the number of measured cables was limited, the lifetime of this type of cable was estimated to be approximately 40 years, even experiencing water immersion. 相似文献
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Ishibashi A. Kawai T. Nakagawa S. Muto H. Katakai S. Hirotsu K. Nakatsuka T. 《Dielectrics and Electrical Insulation, IEEE Transactions on》1998,5(5):695-706
This review summarizes research on treeing phenomena, i.e. the formation of electrical trees and water trees, that has been undertaken in Japan for the development of 500 kV XLPE cable. Section 1 presents the results of factors affecting XLPE cable insulation breakdown under commercial ac and lightning impulse voltages. Section 2 verifies the phenomena of electrical tree formation in XLPE cable insulation using block samples and model cables, and gives the results of studies to determine the level electrical field stress initiation for such trees. Section 3 summarizes the results of studies on long-term aging characteristics, which is a particular problem under commercial ac voltages, while Section 4 explains how this research influenced the design of 500 kV XLPE cable insulation. All authors were members of `The investigation committee of fundamental process of treeing degradation' under IEEJ 相似文献
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The results of a study performed on crosslinked polyethylene (XLPE) insulated cables tested in the laboratory under accelerated conditions are described. URD-type cables rated at 15 kV were aged at 60 Hz, 6 kV/mm, (150 V/mil) and load cycled daily to 90°C conductor, with water inside the pipe and outside of the samples, for periods of up to 3 years. DC testing was performed before and during the aging. An anticipated significant reduction in the AC breakdown strength is observed in control cables (not DC tested), from 44 kV/mm (1100 V/mil) for unaged cables, to 10 kV/mm (250 V/mil), for aged cables. However, there was no further reduction in the AC breakdown strength of cables subjected to DC testing as compared to those that are not tested with DC. It is concluded that AC breakdown strength is not an effective diagnostic tool for determining the effect of DC testing of URD cables aged under the conditions described 相似文献
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AC breakdown tests were performed on field-aged XLPE distribution cables. For these measurements, a special test assembly consisting of air/distilled water terminations was developed. The tested cable specimens were examined for the occurrence of halos and water trees. The results suggest a correlation between the AC breakdown strength and operating stress. The incidence of halos is also found to be related to the AC breakdown strength, but no such relation appears to exist for the water tree length or density 相似文献
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《Electric Power Systems Research》1991,20(2):89-94
The present paper introduces experimental results on treeing breakdown phenomena in actual power cables. Using a water capillary electrode, cable samples immersed in silicone oil have been tested by alternating (50 Hz) and direct voltage stresses. Examination of the needle geometrical breakdown electric field strength resulted in a detailed analysis of the influence of temperature and the presence of water on the breakdown of XLPE cables under divergent fields. 相似文献
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Five 69 kV XLPE cables, 6 to 23 years in service and two old vintage cables from storage plus a 115 kV XLPE cable from service together with a spare cable from the same production, kept in storage, were evaluated. All components of the cables were found to show little signs of deterioration except for AC breakdown. The 69 kV XLPE cable from service has breakdown levels ranging from 10.2 to 18.2 kV/mm, the spare cable 15.0 to 17.7 kV/mm compared to 27.2 kV/mm, the only previously reported value for a new cable. The 115 kV XLPE cable had a breakdown level of 16 kV/mm and the spare 10 kV/mm. The above cables are low-stress cables. Most modern cables operate at higher voltage stresses, taking advantage of cleaner insulations with smoother shields and moisture barriers. Caution is advised in using older, low-stress cables placed in storage 相似文献
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Cable made with Dow HFDA-0587 BK,HFDB-4202 EC,and HFDA-0693 BK was found to meet DL/T 1070-2007 requirement of tree retardant XLPE(TR-XLPE) power cable.The alternate-current breakdown(ACBD) value after 360 days of accelerated water treeing test(AWTT) was 29 kV/mm,which exceeds the DL/T 1070-2007 requirement of at least 20 kV/mm.Cable made with semiconductive shield materials from other material suppliers and HFDB-4202 EC,however,failed to meet DL/T 1070-2007 requirement of at least 20 kV/mm after 360 days of AWTT.This failure to meet DL/T 1070-2007 requirement,apparently,was caused by the high content of ionic contaminants and ash levels in the semiconductive shield materials.The results in this report suggest the use of clean semiconductive shield materials is necessary,in conjunction with tree retardant insulation material,for cables to meet the higher performance TR-XLPE DL/T 1070-2007 requirement,which will enhance system reliability by extending cable life,while lowering life cycle costs. 相似文献
16.
Amyot N. David E. Lee S.Y. Lee I.H. 《Dielectrics and Electrical Insulation, IEEE Transactions on》2002,9(3):458-466
Residual mechanical stresses from manufacturing always exist in freshly extruded HV cables. These stresses are not uniformly distributed in the cable insulation bulk material. Five different HV cables were analyzed with respect to residual mechanical stresses and dielectric breakdown strength. Photoelastic measurements have been carried out and show that maximum residual stresses range from 4.5 to 6 MPa and are located near the conductor shield. Breakdown strength measurements with respect to mechanical stresses have also been performed up to, and above the maximum stresses observed. A significant decrease in ac breakdown strength was observed for stresses higher than 6 MPa. Typical crosslinking by-products from dicumyl peroxide (DCP) have been measured by FTIR spectroscopy at five radial positions in the insulation bulk. Measured by-products consisted in acetophenone and cumyl alcohol. FTIR measurements show that crosslinking by-products content is higher in the bulk of the insulation than near the conductor and insulation shields thus showing a diffusion process. Moreover, residual amount of cumyl alcohol is generally between 1 and 3 times that of acetophenone. No important effect of both by-products on the ac dielectric breakdown strength was observed 相似文献
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This paper provides information on the aging of URD power cable insulated with a tree-retardant crosslinked polyethylene (TR-XLPE) compound, installed in a typical utility environment, Numerous evaluations were performed on samples of power cables aged up to 7 years in-service. AC and impulse voltage breakdown data are compared with data for similar 35 kV ethylene propylene rubber (EPR) and crosslinked polyethylene (XLPE) insulated cables removed from the same utility system. The data show that, to date, the rate of degradation of TR-XLPE cables is less than that of the EPR and XLPE insulated cables. Extrapolation of the data, assuming the same rate, indicates TR-XLPE cable will have the longest life 相似文献
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Tomiyuki Tsujimoto Masahiko Nakade Yukihiro Yagi Noboru Ishii 《Electrical Engineering in Japan》2008,165(4):52-59
A water tree is one aspect of the degradation of XLPE cables used for underground distribution or transmission lines. We have developed the loss current method using the third harmonic in AC loss current for cable diagnosis. The harmonic components in loss current arise as a result of the nonlinear voltage– current characteristics of water trees. We confirmed that the third harmonic in the AC loss current has good correlation with respect to water tree growth and breakdown strength. After that, we applied this method to the actual 66‐kV XLPE cable lines. Up to now, results on over 130 lines have been obtained. In the case of cable lines terminated at gas‐insulated switchgear (GIS), we have to remove the lightning arrestor (LA) and the potential transformer (PT) from the test circuit. The reason is that we are afraid that each LA and PT disturbs the degradation signal from cable lines. It requires extra time (1 or 2 days) and costs more to remove the LA and PT in GIS from a circuit. In order to achieve easy and reasonable diagnosis, we have developed a new method for cable lines terminated at GIS by utilizing a technique that enables one to cancel the signal of the LA and PT from disturbed signal of the cable lines. We confirmed the effect of the new method through experiments with actual cables. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 165(4): 52–59, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20510 相似文献
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热老化对交联聚乙烯电缆绝缘中水树的影响研究 总被引:1,自引:2,他引:1
热老化过程不但会影响交联聚乙烯电缆绝缘的电磁学和物理化学性能,还对绝缘内水树的产生与生长有着一定的影响。通过研究热老化过程对XLPE电缆绝缘中的水树现象的影响,以及在几个有可能的影响因素当中,哪个因素对水树现象的影响最大。实验结果表明,在与XLPE电缆绝缘的热老化有关的各种因素对水树现象的影响中,热氧化对XLPE电缆绝缘表层水树的产生和生长的影响最大。尽管热氧化所引起的缺陷有可能就是XLPE电缆绝缘中水树生长过程中的起始点,但是它在一定程度上抑制着水树的成长,甚至有着"水树延迟效果"的美称。 相似文献