Effects of voltage surges on extruded dielectric cable life projectupdate

Electric utility engineers have commented that extruded distribution cables frequently fail during or shortly after a thunder storm. These engineers also comment that failures often reoccur on cable circuits where previous failures were located with a thumper. Linemen at Georgia Power often make similar comments. To investigate this observation, crosslinked (XLPE) and tree retardant crosslinked (TRXLPE) power cable designs were subjected to accelerated water treeing tests. Samples were subjected to simulated lightning surges or simulated thumping surges. Crosslinked cables removed after 15 years of service operation were also subjected to these surges. The results show that, in some cases, lightning surges do reduce extruded distribution cable life. Also, high level thumping surges appear to reduce cable life once cables are well aged     

基于相位定位装置的中压电缆终端头运行电压定位方法研究

为了在线获取中压电缆的运行电压相位,为局部放电检测提供相位信息,提供了一种定位中压电缆运行电压相位的装置和方法。利用自制的金属贴片传感器在电缆终端头处耦合电压,通过分压原理在示波器得到金属贴片传感器上的电压相位,再通过对获取电压相位信息的反推得到电缆运行电压相位。该相位定位装置主要由金属贴片传感器、示波器以及同轴电缆构成。首先通过对相位定位装置进行电路模型等效和理论推导,计算出相位定位装置测得的电压相位与实际运行电压相位之间的相角差。最后在10 kV电缆终端头上进行实测,论证该理论分析的正确性和该方法的可靠性。在实验过程中还探索了在中压三相电缆终端不同位置进行测试对电压相位偏移角的影响,找到了测试的最优位置。     

Development of extruded ethylene propylene rubber insulated superconducting cable

A superconducting power cable is one of the promising ways of underground transmission of huge electric power in the future. The authors have long proposed the idea of the extruded polymer insulation for superconducting cables. The prominent features of the design are to exploit the excellent electrical properties of polymer in the cryogenic temperatures and to separate the helium coolant from the electrical insulation. Although the extruded cross-linked polyethylene cable has proved ability at the liquid nitrogen temperature, the cable insulation cracked due to mechanical stress during cooling to the liquid helium temperature. To overcome this problem, ethylene propylene rubber (EPR) was selected as a new insulating material considering the good results of mechanical and electrical tests of EPR samples at cryogenic temperatures. An extruded EPR insulated superconducting cable 15 m in length was fabricated and a cooling test down to the liquid helium temperature and a voltage test at the liquid helium temperature were carried out with fair success. This is a breakthrough in terms of the electrical insulation design of cryogenic cables.     

电力电缆护层电压补偿装置研究

电力电缆线路改造时容易造成换位的电缆三段不等长,从而引起护层电压不平衡,产生护层环流。在对电缆护层电压理论分析的基础上,推导了电缆几种主要排列方式下的护层感应电压数学模型;提出了电缆护层电压的补偿方法。该方法是在电缆终端增加一补偿电感,即在铁芯上绕制线圈,此线圈一端接电缆金属护层末端,另一端接地,基于这一补偿方法开发了补偿装置计算的软件包,并进行仿真计算,在此基础上研制了补偿装置。通过改变该补偿装置的气隙和匝数,可以对电缆护层电压进行有效补偿,使补偿后电缆护层的总电压大为减小,有效地抑制了护层环流,可大幅度降低电缆损耗,提高电缆传输容量。     

Application of dielectric response measurement on power cable systems

Water treeing is one of the factors leading to failure of medium voltage XLPE cables in long-term service. Increased moisture content inside oil-paper insulated cable is not desirable. To identify water tree degraded XLPE cables or oil-paper cables with high moisture content, diagnostic tests based on dielectric response (DR) measurement in time and frequency domain are used. Review of individual DR measurement techniques in the time and frequency domains indicates that measurement of one parameter in either domain may not be sufficient to reveal the status of the cable insulation. But a combination of several DR parameters can improve diagnostic results with respect to water trees present in XLPE cables or increased moisture content in oil-paper cables. DR measurement is a very useful tool that reveals average condition of cable systems. However, it is unlikely that DR measurement will detect few, but long water trees. In addition, DR cannot locate the defect or water tree site within the cable system. Combination of DR and partial discharge (PD) measurements can improve diagnostic results with respect to global and local defects. However, it is doubtful whether PD test can identify the presence of water trees inside a cable in a nondestructive manner. Further research is needed for more detailed conclusions regarding the status of a particular insulation and for predicting the remaining life of the insulation system.     

Telephone cable: overview and dielectric challenges

An overview of the common types of telephone wire and cable used in the United States and of related industry specifications is provided. Common insulating materials and selected electrical and physical parameters are discussed, along with several dielectric-related problems facing the industry. One is to reduce the migration of oil from cable filling gels into the insulation, where it adversely affects the electrical and physical properties. A second problem is how to reduce the overall fire hazard contributed by wire and cable installed in a building. A third problem is to develop twisted-pair copper cables that can handle increasingly higher data rates     

用交流电压进行高压XLPE绝缘电缆线路的现场试验

根据XLPE绝缘电缆用直流电压进行现场试验的经验,要求开发新的方法。现在有一种移动式调频串联揩振装置能够用交流电压进行试验,这意味着适用于塑料绝缘电缆敷设后的试验将有重大突破。配有经由户外户内开关设备而接至电缆线路的连接线,以满足不同用户的要求。     

挤出铝管式电力线光缆的探讨

介绍了挤出铝管式电力线光缆,其中光纤被直接放入一根挤出的铝管中而组成一个光纤单元,它不但可以用来制造OPGW、OPPC等架空光缆,而且也可以用来制造地下光缆和海底光缆。文章描述了这种光缆的特点,并报道了按照IEC60794和IEEE1138等标准进行的型式试验、耐腐蚀试验以及传递到支撑结构上的机械张力测试情况试验,结果表明,这种新式光缆符合国际标准,不仅保留了传统OPGW的光学机械、电气特性,而且其抗化学腐蚀、抗雷击和减缓机械张力等性能均有所提高。     

全介质自承式光缆（ADSS）的电腐蚀

叙述了工程中ＡＤＳＳ光缆的电腐蚀现象,分析产业电腐蚀的主要原因,从而提出对电力系统ＡＤＳＳ光缆设计的几点意见。     

高压电缆故障测寻及定位方法

介绍了高压电力电缆的故障类型、故障查找步骤以及国内外常用的故障检测方法。通过对高压电力电缆的故障部位、故障类型以及相对应的预定位方法以及对其精确定位的分析和探讨,较为全面地提出了一整套行之有效的电力电缆故障测试方法。     

基于泄漏电流的高压电缆线路故障测距方法

为实现高压电缆线路短路故障发生后准确故障定位,提出一种利用故障通道泄漏电流的离线故障测距方法。该方法在短路故障发生后于电缆终端加直流电压,泄漏电流主要通过故障击穿通道沿金属护层流入两端接地点,在线路两端接地点检测护层电压,通过单位长度金属护层阻抗与泄漏电流和护层电压的关系,可计算出故障点位置。仿真结果表明,该方法能够有效的定位故障点位置,其相对误差不超过8%,绝对误差不超过50 m。     

Impulse breakdown superposed on ac voltage in XLPE cable insulation

This paper discusses tree inception and breakdown voltage characteristics of XLPE cable insulation subjected to impulse voltages superimposed on ac voltage. The tree initiation tests were performed on laboratory-molded specimens equipped with needle electrodes, whereas the breakdown tests were conducted on a full-sized cable. The impulse tree initiation stress was found to be dependent on the magnitude of the pre-applied ac stress and the relative polarities of the impulse and the ac peak at the instant of their superposition. Although the impulse polarity has an effect on the tree inception, the general behavior is that the tree inception stress always decreases with an increase of the pre-applied ac stress. This phenomenon is discussed in terms of the space charge effect and the influence of the impulse voltage application itself. The impulse strength of a full-sized cable insulation was found to be independent of the pre-applied ac stress as long as that stress did not exceed the operating stress of a 500 kV cable insulation. However, subjecting cable insulation to higher ac stresses before impulse application caused a reduction of its breakdown strength as compared with the insulation without ac prestressing     

基于低压电力线载波通信的电缆防盗系统

针对低压配电电缆屡屡被盗的现状,设计了基于电力线载波通信的电缆防盗系统。该系统分为发送端和接收端,分别安装在电缆的两端。发送端以固定的时间间隔持续发出载波信号,载波信号通过电缆传输,接收端接收两次发送端发出的信号超过一定的时间间隔则认为电缆已被盗剪,系统发出报警信号。电力线载波通信模块采用电力线载波Modem芯片SSC P300,单片机采用的是M68HC11E9芯片。该电缆防盗系统具有较好的应用前景。     

振荡波电压作用下的电缆介质损耗测量方法

介质损耗是评价电力电缆绝缘状态的重要指标之一。振荡波电压作为目前新兴的检测电压,因具有与工频交流电压较好的等效性,在局部放电检测领域有广泛的应用,但振荡波电压下的介质损耗测量工作暂未深入开展,对绝缘状态一体化检测具有局限性。为了解决目前的局限性,文中提出了一种基于振荡波测试技术的电缆介质损耗测量方法。在振荡波测试系统每次工作期间,采集电缆试品的电压或电压、电流数据,然后通过数据后处理提取波形参数,从而获得准确的介质损耗。文中同时对2种基于振荡波电压的介质损耗测量方法进行对比与现场误差分析,得到基于振荡波电压、电流波形的介质损耗角测量方法,具有较高的准确性以及实用性,并提出了解决零点漂移的方法。最后,仿真以及实验结果验证了该方法的可行性和有效性。     

老化中压电缆复合界面的放电特性研究

针对中压电缆热缩型中间接头界面受潮老化的放电特性做了相关研究,分别在不同的湿度环境下做了两类中间接头样本。通过对干燥电缆接头和受潮电缆接头界面间的放电特性做了对比,将整个放电过程分成了三个阶段,分别对比这三个阶段的不同放电特征。对击穿后的样本进行了解剖,观测到受潮界面和干燥界面绝缘失效后的电痕有差异。分析了造成放电特性和电痕差异的主要原因。得出了由于界面间水的作用,使得界面空腔被填满的同时降低了绝缘强度,虽然消弱了初始阶段的局部放电,但增加了后期的击穿概率。而造成不同的电痕特征的主要原因在于干燥界面间的放电对绝缘的劣化具有累积效应,所以放电主要集中在一条通道上。而潮湿界面在水的作用下,界面击穿发生在不同的位置,碳化痕迹分布较广。     

Technical trends in medium voltage URD cable specifications

It has been more than thirty years since high molecular weight polyethylene (HMWPE) was first introduced as a commercial insulating material for medium voltage (15-35 kV) underground residential distribution (URD) cables. That began a dramatic expansion of utility electrical service that has led to the installation of several million miles of URD cables by over 3,000 utility companies across America. When early cables began failing prematurely, the industry was challenged to diagnose the causes and find corrective solutions that would give utilities the confidence to continue their commitment to underground cable. The past 25 years have been a story of constant technical improvements, increasingly tighter industry specifications and positive advancements in URD cable life performance. This paper discusses the significant technical changes that have taken place during this period and their impact on cable performance. The results of a 1983-1993 ten-year study of the major technical specification changes of the 25 largest Investor-Owned Electric Utility Companies (IOUs) is also presented. The data illustrate how quickly new cable technology is specified by these leading utilities and provide a clear picture of the key technical trends occurring throughout the utility industry during the 1990s     

一种可用于高电压的电缆绕组变压器

介绍了一种基于交联聚乙烯电缆绕组的新型电力变压器。与传统的油浸式和干式电力变压器相比,新型电缆变压器具有电压等级高、容量大、阻燃不爆、高环保、安全可靠等特性,因而具有广泛的应用前景。     

线缆测试仪输出电压校准方法研究

线缆测试仪输出电压具有内阻高、时间短等特点,传统的方法不能满足校准的要求,从而导致结果不准确。为解决这些问题,该文在制定 JJF 1457-2014的过程中,选取典型线缆测试仪进行源内阻实验,选取常用的电压表进行响应时间实验。实验证明,线缆测试仪内部电压源阻抗大约为10 kΩ~2 MΩ,电压表响应时间约为0.5~1.0 s。通过实验,获得了应选用内阻高于1 GΩ以及响应时间应小于被校仪器输出电压持续时间的标准电压表的结论。