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1.
刘英  曹晓珑  王乐 《高电压技术》2008,34(3):468-471
为了研究交联聚乙烯电缆绝缘中的残余应力及其随温度的变化与松弛情况,利用电阻应变计与电阻应变仪连接的试验线路,在升温至80°C和90°C以及在这两个温度下的保温过程中,测量了绝缘截面上不同部位的应变量。试验发现,生产过程导致交联聚乙烯绝缘层中存在残余机械应力/应变以及半径方向的形态不均匀,这是导致电缆性能下降的重要原因,尤其对绝缘较厚的高压和超高压电缆,需恰当的热处理工艺消除其影响,改善绝缘性能。所提测试方法简单易行,可与计算机连接完成自动连续测量,因此可用于工艺参数的优化设计。  相似文献   

2.
为研究温度对直流电缆用交联聚乙烯绝缘性能的影响,选取了2种具有代表性的直流电缆用交联聚乙烯和1种交流电缆用交联聚乙烯进行对比研究。分别对其在不同温度下的直流电导率和空间电荷集聚特性进行分析。结果表明:在温度范围为20~70℃时,3种交联聚乙烯试样的直流电导率随着温度的升高呈指数增大,但电导活化能有差异,直流电缆用交联聚乙烯的电导率随温度升高的变化程度较小;交流电缆用交联聚乙烯以积聚负电荷占主导,而2种直流电缆用交联聚乙烯空间电荷的平均电荷密度较小。此外,3种材料在常温下的直流击穿场强差异明显;红外光谱结果表明直流电缆用交联聚乙烯具有更少的羰基基团。2种直流电缆用交联聚乙烯分别采用提高纯净度和引入无机填料2种方式,使直流介电性能得到了改善。  相似文献   

3.
脱气热处理工艺广泛应用于交联聚乙烯(XLPE)电缆的生产过程中,并对其性能有重要的影响。通过对数根完整切断的110 kV交流XLPE电缆分别进行不同温度和不同时间的脱气热处理,之后对其切片进行红外光谱分析、力学性能测试和介电性能测试,研究脱气热处理对XLPE性能的影响。结果表明:110 kV XLPE电缆绝缘层中的交联副产物主要是苯乙酮和枯基醇,交联副产物挥发速率随着脱气温度的升高而增大。结合交联副产物的挥发速率、生产成本和高温对电缆线芯的危害等因素考虑,110 kV XLPE电缆合理的脱气温度为70℃。交联副产物的含量随脱气时间的增加而减小,168 h后减小趋势减缓,至336 h时不再显著变化,因此XLPE电缆合理的脱气时间应控制在168~336 h。脱气时间对XLPE断裂伸长率的影响仅限于脱气处理初期,断裂伸长率随脱气时间的增加而增大,之后不再显著变化,将脱气时间控制在168~336 h能有效改善各层绝缘的力学性能。XLPE的介电常数和介质损耗均随脱气时间的增加而减小,但是当脱气时间超过168 h后,各层试样的介电性能变化不明显。  相似文献   

4.
保守的绝缘厚度设计增加了电缆的生产成本,同时导致了击穿场强的减小,降低电缆性能。因此,高压直流电缆绝缘击穿场强的厚度效应研究具有工程实际意义。选取高压直流电缆用交联聚乙烯国产直流料作为研究对象,通过对不同厚度试样进行30、50、70℃下的直流击穿实验和空间电荷测试,研究温度对于交联聚乙烯击穿场强厚度效应的影响与机理。研究结果表明:交联聚乙烯的直流击穿场强随温度升高而降低,不同温度下交联聚乙烯的击穿场强与厚度的关系符合反幂定律,指数因子随温度变化,30℃时为0.41,50℃时为0.71,70℃时为0.56;30℃时,交联聚乙烯空间电荷密度和电场畸变与厚度呈正相关,导致击穿场强降低;随着温度升高,空间电荷积累增多,电场畸变增大,在薄试样中这种变化更为明显。实验结果说明,温度作用下的交联聚乙烯击穿场强的厚度效应与聚合物自由体积的变化、内部热量的积聚、空间电荷的二次效应等因素密切相关。  相似文献   

5.
为研究应急负荷变动下高压单芯电缆的线芯温度响应特性,建立了应急负荷变动下高压单芯电缆线芯温度随时间变化的梯度函数,以110 kV交联聚乙烯单芯电缆为研究对象,设计了水中敷设、空气中敷设、土壤中直埋的3种条件下高压单芯电缆应急负荷变动的温升试验。结果表明:当高压电缆负荷发生应急变动时,线芯温度随时间的梯度变化受环境影响很大,其中空气敷设电缆线芯温度的变化梯度最大,水中敷设电缆线芯温度变化梯度最小,土壤敷设电缆线芯温度变化梯度介于前两者之间。在3种敷设条件下,电缆线芯温度的梯度变化都随应急变动负荷的增加而增大。  相似文献   

6.
加速水树老化对XLPE电力电缆绝缘性能的影响   总被引:4,自引:3,他引:1  
交联聚乙烯(XLPE)因具有稳定的理化性能和良好的电气性能而被广泛应用于中高压电缆绝缘中,而电缆长期运行会导致其内部绝缘的化学成分和物理形态的变化。为此,通过加速水树老化实验研究了水树老化对10kV交联聚乙烯电缆绝缘材料理化性能和介电性能的影响。随着老化时间的延长,发现电缆的外层绝缘首先发生化学结构变化,结晶度和密度减小,试样内外层热失重温差增大,熔融温度点向低温偏移,并且发现在介电损耗谱的低频段出现了新的损耗峰。理化和介电两个方面的分析结果表明,老化首先发生在外层绝缘,在电应力和机械应力的作用下,绝缘内部出现微观缺陷,表现为微观结构的变化。提出加速水树老化的物理和化学过程,阐明了水树老化过程对电缆绝缘材料性能的影响机制。  相似文献   

7.
为研究交联聚乙烯(cross-linked polyethylene,XLPE)绝缘材料的热分解活化能、电气特性和力学特性随热老化程度变化的规律,对交流电力电缆绝缘用XLPE材料在110 ℃下开展加速热老化实验。采用热失重(thermogravimtric analyzer, TGA)测试手段,对XLPE在20~600 ℃的热分解行为进行研究;采用交流击穿测试、宽频介电谱测试及体积电阻率测试,研究老化后XLPE试样的电气特性;采用拉伸实验测试,研究老化后XLPE试样的力学特性。结果表明:热老化使得XLPE的交联结构和结晶状态被破坏,XLPE活化能呈减小趋势。由于氧化反应快速进行,使得XLPE分子链发生断裂,交联结构变弱,导致XLPE绝缘材料严重劣化,其活化能、击穿强度、体积电阻率、弹性模量和断裂伸长率随老化时间增长呈下降趋势,而介电常数、介电损耗和电导率呈增加趋势。  相似文献   

8.
为研究交联聚乙烯(cross-linked polyethylene,XLPE)绝缘材料的热分解活化能、电气特性和力学特性随热老化程度变化的规律,对交流电力电缆绝缘用XLPE材料在110 ℃下开展加速热老化实验。采用热失重(thermogravimtric analyzer, TGA)测试手段,对XLPE在20~600 ℃的热分解行为进行研究;采用交流击穿测试、宽频介电谱测试及体积电阻率测试,研究老化后XLPE试样的电气特性;采用拉伸实验测试,研究老化后XLPE试样的力学特性。结果表明:热老化使得XLPE的交联结构和结晶状态被破坏,XLPE活化能呈减小趋势。由于氧化反应快速进行,使得XLPE分子链发生断裂,交联结构变弱,导致XLPE绝缘材料严重劣化,其活化能、击穿强度、体积电阻率、弹性模量和断裂伸长率随老化时间增长呈下降趋势,而介电常数、介电损耗和电导率呈增加趋势。  相似文献   

9.
高压交联聚乙烯(XLPE)电缆长期在振动环境中运行时将导致绝缘结构疲劳损坏,为了分析交联聚乙烯电缆固有频率与外部振动耦合条件下的位移与内部应力分布,在简支梁固有频率计算及振动模态分析的基础上,仿真获得了不同敷设条件下外部频率对电缆内部应力、位移分布的影响。仿真结果表明:铁路桥梁敷设电缆时,敷设距离的制约使得电缆固有频率处内部应力、位移最大值都急剧增大;隧道敷设电缆时,其内部应力、位移分布呈周期性波动;在共振与非共振频率下,内部应力、位移的大小相差很大;经仿真计算得出,隧道内500 kV交联聚乙烯电缆的敷设间距应小于3.42 m,以防止电缆共振。根据电缆模态分析,提出交联聚乙烯电缆在强振动区域敷设时应适当减小电缆夹具间距,避免外部频率与电缆固有频率耦合产生共振而导致电缆损坏,这对制定强振动区域内电缆敷设方式及运维策略具有指导意义。  相似文献   

10.
《高电压技术》2021,47(9):3181-3188
硅橡胶凭借其高弹性与优良的电气性能,广泛应用于预制式交联聚乙烯高压电缆接头的主绝缘中。但长时间的异常温升会加速材料的老化,导致其相关性能的下降,从而引发事故。为此设计并开展了预制式高压电缆接头绝缘用硅橡胶的加速热老化试验,对比分析了其热老化前后的微观结构、力学性能、电学性能与声学性能。结果表明:热老化后电缆接头硅橡胶绝缘残余的交联副产物挥发,侧链有机含量降低,主链间发生交联;随着老化温度与时间的增大,试样的断裂伸长率与拉伸强度逐渐下降,杨氏模量逐渐上升,导致柔顺性变差,材料逐渐硬化,弹性丧失;体积电阻率与相对介电常数略有上升,变化不明显,介电损耗因数随热老化的进行而降低;热老化后电缆接头绝缘用硅橡胶的超声声速显著增大,测试结果符合相关理论公式,与杨氏弹性模量的变化趋势良好对应,在评估电缆接头硅橡胶绝缘的热老化状态有广阔的应用前景。  相似文献   

11.
Crosslinked polyethylene (XLPE) and low-density polyethylene (LDPE) insulations used in HV cables are not only subjected to electrical and thermal stresses, but also exposed to mechanical stresses, whether residual internal stresses created during the cooling process of the fabrication, external forces when cables are bent during installation or thermomechanical stresses caused by differential thermal expansion between the conductor and the polymeric material. In order to investigate the possible influence of mechanical stresses on dielectric properties of polyethylene, measurements were conducted on pin-plane XLPE and LDPE samples with various magnitudes of residual mechanical stresses around the embedded electrode. The time to inception, the growing rate and the shape of the electrical trees under different voltages are reported in this paper. Specimens with the highest values of residual stresses were found to have the shortest inception times and the longest trees after one hour of aging under different voltages. When the mechanical stress was allowed to relax, the treeing resistance was measured to be significantly improved  相似文献   

12.
The effects of such constituents as the crosslinked part, non-crosslinked LDPE part, antioxidant, and residual byproducts on the formation of space charge in XLPE have been investigated. It has been found that homocharge is developed in the pure crosslinked part of XLPE. The non-crosslinked LDPE part encourages the formation of heterocharge, although its influence is not strong. Residual byproducts generated during the crosslinking reaction encourage the formation of heterocharge, whereas antioxidant was found to prohibit the formation of heterocharge. Of these, residual byproducts have been found to impose the most pronounced influence on the formation of heterocharge in XLPE, so that only heterocharge is found in an as-pressed XLPE with semiconductive electrodes  相似文献   

13.
Contents  This paper describes results of laboratory accelerated aging test and the influence of different aging conditions on non-electrical properties of cross-linked polyethylene insulation (XLPE). Accelerated aging has been carried out on a cable model with different electrical and thermal stresses, and with thermal stresses in air or water as surrounding environment. Tensile strength, elongation at break, degree of cross linking and crystallinity degree of XLPE insulation have been measured and monitored. Received: 10 April 2000  相似文献   

14.
This work the combined electrical and thermal stresses of the 154 kV XLPE power cable used in the underground power transmission in Turkey. The dependence of aging on electrical and thermal stresses is given by a straight line in a certain range of electric field (E) values which indicates that the aging is a thermochemical process. Furthermore, cable tests are conducted in oil, and the results are valid for immersed insulation but might not be completely representative of XLPE used in service in a "dry" environment. Therefore, each cable insulator has to be tested and the parameters must be determined for each cable separately.  相似文献   

15.
The electrical properties such as water tree length, electrical conduction, ac breakdown strength and space charge of silane crosslinked polyethylene (SXLPE) were investigated, with a purpose to compare this material with ordinary dicumyl peroxide (DCP) crosslinked polyethylene (XLPE). Experimental results show that SXLPE has a smaller water tree length, much lower conduction current density, a little bit higher ac breakdown strength than XLPE, and on SXLPE only a very small homocharge is seen. The better behaviour of SXLPE under electric stress is attributed to the absence of residual curing byproducts present in XLPE and the change of chemical structure by grafting and curing reactions  相似文献   

16.
Water trees in the insulator of XLPE cable may considerably reduce the dielectric breakdown voltage, thus being an important lifetime‐governing factor. The ac superposition method we have investigated is a new technique for hot‐line diagnosis of 6.6‐kV XLPE cables, and the diagnostic apparatus using this technique is now widely used in the distribution line field. In order to study the application of the ac superposition method to degradation diagnosis of 22/33‐kV class XLPE cables, we measured deterioration signals of the cables with water trees by a modification of the above diagnostic apparatus. The deterioration signals, hereafter called “ac superposition current”, were generated by an amplitude modulation effect due to the nonlinear resistance of water trees. Moreover, we evaluated the relationship between the ac superposition current and the ac breakdown voltage. It is difficult to judge whether a correlation between then is present or not because of the uneven distribution of the measured data. However, the ac superposition current tends to increase linearly with a decrease in the residual thickness of the insulator. For example, the ac superposition current was about 40 nA when the residual thickness decreased to 3 mm. Thus, we consider that the ac superposition method is effective for degradation diagnosis of 22/33‐kV class XLPE cables.  相似文献   

17.
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   

18.
The design, manufacture and testing of crosslinked polyethylene (XLPE) cables for voltages of 245 kV and above are described. The operational reliability of a cable connection is decisively codetermined by the reliability of the cable accessories. The state-of-the-art and development trends regarding cable-sealing ends and cable joints are discussed in detail. Knowledge of the lifetime curve of XLPE (essential for designing reasonable qualification tests) is discussed, and test results which show that service stresses of 12-13 kV/mm can be realized are described. The design of accessories, especially joints and terminations for enclosed switchgears is addressed, and service experience is reported  相似文献   

19.
XLPE电缆绝缘中的电树枝结构及其生长特性   总被引:13,自引:4,他引:9  
为研究不同频率下半结晶XLPE电缆绝缘材料中的电树枝引发、生长及结构特征,系统的归纳了XLPE电缆绝缘中可能出现的电树枝特征及其与材料聚集态和残存应力的关系;采用变频高电压发生器、实时显微数字摄像技术及专用试样加工工艺,进行了大量的电树枝培养实验。实验研究发现,由于半结晶高聚物的不均匀结晶和电缆生产过程中在绝缘层中产生的残存应力的影响,使得50Hz施压频率下XLPE电缆绝缘试样中会生成枝状、枝状与丛林混合状及纯丛林状3类电树枝,而>500Hz高频下则只能生成稠密枝状电树枝,它们分别对应于不同的生长机理。低频下电树枝生长特性和电树枝结构与材料的聚集态密切相关,而高频下则关系不大。分形分析这些电树枝的结构后发现,电树枝的生长特性与其分形维数及其分形维数的变化有对应关系,故可用分形维数分类和定量描述这些电树枝.最后探讨了几种不同结构电树枝的生长机理。  相似文献   

20.
A test cycle with electrical, thermal and combined stresses has been performed on models of XLPE insulated: cables in order to characterize this type of cable from the viewpoint of endurance to combined stresses. For this purpose the method of Combined Analysis of experimental data has been used, thus permitting the goal to be reached in less than two years. The experimenrtal methods and theoretical procedures are illustrated in the paper and the results shown by means of the three basic graphs for combined stresses. The material Under test has shown good endurance : values; of electrical and thermal threshold high enough to provide a reference for operating stresses. Some values for the stresses applicable in service are suggested.  相似文献   

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