Electrical conduction in HVDC mass-impregnated paper cable

HVDC cables play an important role in a growing number of HVDC links. For almost all of these cables, mass impregnated paper is used as electrical insulation. The electrical conductivity of this insulation is given by a commonly used empirical formula. This formula takes into account the temperature and stress dependency of the conductivity. This paper derives a physics-based equation describing ionic conduction. In good approximation this theoretical formula gives the same results as the empirical one. This makes it most likely that the conduction in paper mass impregnated cables is of the ionic kind. The derived formula uses some physical parameters like the inter-potential well distance, the potential well depth and the carrier concentration. Numerical values of these quantities for mass impregnated paper are given. According to the proposed model, the stress dependency results from the inter-potential well distance only. The temperature dependency results merely from the depth of the potential energy wells. In addition some possible underlying physical processes are described     

一起220 kV XLPE交联电缆故障分析和研究

某水电厂新投运的220 kV交联电缆运行中突然发生故障,电缆导体对屏蔽形成贯穿性故障.为分析寻找引发故障原因,对电缆进行解剖试验分析,认为电缆可能存在外半导层贯穿性损伤,并对结果进行了验证试验和有限元电场模拟计算分析,结果与结论相吻合.     

变电站主电气设备在线监测的研究

阐述了在线监测系统的重要性和优点，指出了在线监测的必要性。分析现代变电站主电气设备在线监测的现状，介绍了变电站中主电气设备实现在线监测的方法，对其中几种监测方法进行比较，并且结合现在的前沿技术应用，指出了变电站主电气设备故障涉及的方面，以及在线监测重点。最后对于在线监测技术的发展方向进行展望。     

变电站主电气设备在线监测的研究

阐述了在线监测系统的重要性和优点,指出了在线监测的必要性.分析现代变电站主电气设备在线监测的现状,介绍了变电站中主电气设备实现在线监测的方法,对其中几种监测方法进行比较,并且结合现在的前沿技术应用,指出了变电站主电气设备故障涉及的方面,以及在线监测重点.最后对于在线监测技术的发展方向进行展望.     

Electrical treeing characteristics in XLPE power cable insulation in frequency range between 20 and 500 Hz

Electrical treeing is one of the main reasons for long term degradation of polymeric materials used in high voltage ac applications. In this paper we report on an investigation of electrical tree growth characteristics in XLPE samples from a commercial XLPE power cable. Electrical trees have been grown over a frequency range from 20 Hz to 500 Hz and images of trees were taken using CCD camera without interrupting the application of voltage. The fractal dimension of electric tree is obtained using a simple box-counting technique. Contrary to our expectation it has been found that the fractal dimension prior to the breakdown shows no significant change when frequency of the applied voltage increases. Instead, the frequency accelerates tree growth rate and reduces the time to breakdown. A new approach for investigating the frequency effect on trees has been devised. In addition to looking into the fractal analysis of tree as a whole, regions of growth are being sectioned to reveal differences in terms of growth rate, accumulated damage and fractal dimension.     

中国电器工业协会第二届会员代表大会在京召开

中国电器工业协会第二届会员代表大会于2001年5月21日至23日在北京召开,近300名代表参加了会议.     

中国电器工业协会2001年工作巡礼

2001年是新世纪的第一年。这一年,我们伟大祖国在改革开放和现代化建设中,高歌猛进,步伐雄健,经济仍然保持较好的发展势头,GDP增长7.3％。这一年,电工行业广大职工坚持改革,奋力拼搏,生产经营继续保持稳定增长的态势,预计产品销售收入将比去年增长14％～15％。这一年,中国电器工业协会在业务主管部门的指导和支持下,坚持服务宗旨,紧紧依靠分会和会员,认真履行职能,努力为会员服务,为电工行业的改革与发展,做了一系列工作:     

高速列车屏蔽线转移阻抗与屏蔽效能研究

针对高速动车组屏蔽线缆受电磁干扰问题,在单层屏蔽转移阻抗解析法模型的基础上,考虑双层屏蔽对屏蔽层直流阻抗和小孔电感的影响,提出用于计算高速动车组屏蔽线缆转移阻抗的双层屏蔽解析法优化模型。同时结合传输线与屏蔽效能理论,推导屏蔽效能与转移阻抗的定量关系,以及芯线受到传导干扰后的理论数学模型。最后,以某动车组屏蔽线缆为研究对象进行建模仿真,分析线缆受扰情况,对比CST仿真值与计算值,验证了本文所提优化模型的正确性。优化模型在各频段的计算误差均值低于10%,验证了优化模型的有效性。揭示了高速动车组屏蔽线缆的受扰机理。     

领导人员综合考核评价中业绩考核的沿革

完善考核评价的方式、内容、程序，注重对实绩取得过程的考核，把短期效果与长期作用结合起来，综合分析，全面客观地评价领导人员。     

Air temperatures in a deep cable tunnel

The thermal conditions related to the installation of HVDC 400 kV cable circuits installed in a deep tunnel (530 m) are investigated. It is seen that even with natural convection the temperature specification is complied with.     

The simplified method for transient thermal field analysis in a polymeric DC cable

The simplified method of analysis of the thermal field in the futuristic model of a DC cable is presented. The thermal conductivity of a non-conducting layer is very small comparing with the same parameter of conducting regions. The above causes very fast heat propagation in the core and coating, which in the consequences are approximated by inert elements of the first order. Spatial changes in the field in insulation cannot be neglected, because of the significantly slow heat transfer. For that reason, insulation is treated as an element of distributed parameters. The boundary-initial parabolic problem of a non-conducting region is solved by means of Duhamel’s theorem. The fundamental solutions of superposition integrals are determined by the separation of variables method. The maximal deviation of results obtained by the finite element method does not exceed 7.2%. The heating curves and results of verification are presented in a graphic form.     

交联聚乙烯电缆中水树研究的现状

在14篇文献的基础上综述了交联聚乙烯(XLPE)电缆中水树研究现状,介绍了水树的定义、分类、特征及在水树产生和发展过程中的一些影响因素及抑制方法等,并且对水树研究中提出的新机理等做了简要的概括。     

Biomedical engineering: University of Pennsylvania-from researchlaboratory to a leader in educational institutions for bioengineering

The evolution of the Electromedical Laboratory of the Moore School of Electrical Engineering at the University of Pennsylvania into a biomedical engineering department is summarized. Administrative and educational details for the period when the author served as head and chair (1952-1973) are related.     

Electrical Area Classification drawings: a comparison

This article compares the types of Electrical Area Classification drawings that have been prepared for chemical and petroleum processes and highlights the differences and, in particular, the application variations of NFPA 497A and API RP500. It discusses the complexities in applying these standards. Finally, it presents a technique that meets OSHA Process Safety Management requirements and has other significant advantages     

The International Electrical Exhibition of 1884: A Landmark for the Electrical Engineer

The International Electrical Exhibition of 1884, sponsored by the Franklin Institute, was held in Philadelphia fromn September 2 to October 11, 1884. It recorded the past in a historical exhibit and bibliogaphical collection, displayed the present in exhibits of machinery and equipment for the production and use of electricity, and presaged the future in the first public display of a vacuum tube. In competitive tests, Edison's lamps burned for 1000 h but scrificed efficiency. The dynamos of Edison and Weston were tested and found to be equal in efficiency. Concurrent with the Exhibition, a quasi-governmental conference was held, attended by native and foreign scientists and engineer. At this National Conference of Electricans, the tension that existed between the pure scientist and the "practical electrician" becane evident. The science-technology relationship is suggested as one of the reasons for the founding of the American Institute of Electical Engineers (AIEE) in April 1884. The Exhibition is a convenient dividing line between a preelectrical wodd and one in which electric light and power became a fact of life in every aspect of our social and industril environment. It signaled the decline of the individual inventor as promoter of electricity and the begnning of dominance of the professional engineer within a corporate stucture, and showed the state of the electrical art at the time of the AIEE's first technical meetings. The need for a national society of electrdc engineers to receive "foreign electical savants, engineers and manufacturers" attending the Exhibition prompted N. S.     

The calculations of conductive noise and heating of the screen in a control cable

Lighting strokes and short circuits (SCs) are the main sources of conductive noise that propagates along control cables and can lead to the failure of microprocessor equipment in the protection and control systems of electric power substations. Two-sided grounding of the screen of a control cable substantially reduces the pulse and high-frequency conductive noise level, but leads to heating of the screen under short-circuit conditions. The existing standards determine the conductive noise and screen heating as a function of screen voltage that is suitable for a single cable. A more general case that takes into account the cable magnetic coupling with other conductors when current is used as a calculation parameter has been considered. The conductive noise at the first pulse of lightning current is determined using the transfer impedance “screen–cable core” or 3D cable model in the general case. To calculate the heating, the formula of GOST (State Standard) 28895-91, which is rejected in modern standards because of the assumption that short-circuit current is invariable (in fact, the current decreases with heating of the screen), has been used. Using this formula in a step algorithm leads to correct results. The cable magnetic coupling with other conductors is expressed as insertion impedance that increases the screen impedance and decreases the current and screen heating. A numerical experiment for a typical cable has shown that conductive noise and heating of the screen of the cable can be substantially reduced because of the parallel laying of conductors. It has been concluded that, to decrease the conductive noise and heating of the screen of a control cable, it is necessary to decrease the screen current.     

The field test of a cable internally cooled with fire resistant oil

Tricresyl phosphate (TCP), a phosphate ester with fire-resistant and insulating properties, is proposed as a cable cooling medium. A field test was performed with a 275 kV internally-oil-cooled, oil-filled (OF) power cable system using TCP, and it was ascertained that the cable system meets requirements for ease of installation, cooling characteristics, and long-term stability of the cable and the long-term stability of the cable and the TCP. The series of tests has demonstrated the practicality of the cable system