A new approach to underground cable performance assessment

This paper presents a new approach to thermal field sensitivities and ampacity computations of underground power cables using a proposed algorithm of perturbed finite-element analysis. The new approach involves the use of derived sensitivity coefficients associated with various cable parameters of interest, and use these coefficients to achieve optimal cable performance. The proposed model provides a quick methodology, based on the finite-element model, to assess the cable thermal performance subject to variations in the cable thermal circuit parameters. The developed algorithm was applied to various practical cable systems. The effect of multilayered thermal conductivities and boundary parameters variations on the actual cable system ampacity was investigated using the proposed methodology. A comparison was made of the obtained results with the conventional finite-element approach in order to show the applicability and usefulness of the developed methodology. Our objective was to assess the effects of operating parameter variations in a straightforward manner, without repeating the thermal field analysis for each parameter change. The thermal field of an underground power cable sample directly buried in the soil was measured in the laboratory using a developed full-size experimental setup. The investigations involve all parts of the thermal circuit parameters representing cable composition, surrounding soil and boundary phenomena. The experimental setup was used to validate the simulation model by comparing the simulation results with the real laboratory measurements. Such experimental verification confirmed the accuracy of the new introduced finite-element sensitivity methodology.     

阻水型电缆的发展历程

对纵向水密封船用电缆、聚乙烯绝缘填充式挡潮层聚乙烯护套市内通信电缆和阻水型电力电缆等多种阻水型电缆的开发原因和应用情况,以及发展历程作详细介绍,并对电缆的金属护套、铝塑聚乙烯护套、聚乙烯和聚氯乙烯护套的径向阻水性能作了简单比较。     

The calculation of cable parameters using combined thermal andelectrical circuit models

A methodology that can be used to calculate underground power cable ampacities and other cable parameters is presented. Capabilities of the methodology include the ability to model (both thermally and electrically) conductors, shields, and neutrals in an underground cable system. Currents are calculated from the electrical circuit model and are used in the thermal analysis of the cable system. Temperature-dependent parameters are determined on the basis of calculated system temperatures. Solutions of both the thermal and electrical circuit models are performed with an iterative procedure until convergence based on conductor temperature occurs. Results from this procedure include not only the calculation of thermal parameters, such as cable ampacities and system temperatures, but also electrical parameters, such as cable voltage drops and open-circuited shield voltages     

New Approach to Ampacity Evaluation of Cables in Ducts Using Finite Elemet Technique

This paper presents a package of user-oriented computer programs for power cable thermal analysis using the finite element technique. Special features of the programs include: automatic grid generation routine, user friendly input and output structures, sensitivity analysis, combined heat/moisture analysis, and a new, exact method of modeling the heat flux distribution in the region between the cables and the retaining duct in the underground power transmission system. The analysis reveals that the heat flux on the inside surface of the retaining duct is not uniform, as generally assumed in cable ampacity calculations. In fact, the heat flux is maximum at the top where the convection induced flux is much stronger than at the bottom or elsewhere around the duct. Laboratory experimental verification of the heat flux model is presented. A full scale test of a 12 cable system in a concrete duct bank is described and the temperatures measured over a 42-day period are compared with those obtained using the new computer program.     

Cable Selection Methodology for Deep Water Power Transmission System Applications

A methodology has been developed to assist in the technical evaluation of power transmission cable system installation and operational risks and the selection of a cable design for application in deep water installation situations. The methodology involves the evaluation of eight defined technical selection criteria that provide either (1) an index of safety associated with various technical design aspects of a "Candidate" cable, or (2) an indication of the technological difficulty to manufacture, install, repair or operate each cable "Candidate." The cable selection methodology was developed to support the needs of a specific transmission cable application in Hawaii, but the methodology should be readily adaptable to other submarine power cable projects.     

配电电缆中受潮接头的阻抗特性及其检测方法研究

电缆接头是电力电缆中最脆弱的部位,接头受潮是中压交联电缆的常见缺陷,如果未能及时得到修复,将导致电缆过早失效。文章围绕中间接头受潮后的阻抗特性及其检测方法开展研究,阐述了波在电缆中传播的折反射现象,以时域反射法的理论知识为基础,在CST (Computer Simulation Technology) Studio Suite中建立了10kV冷缩式中间接头的三维单芯模型,对中间接头不同程度进水情况下的阻抗特性和反射波形进行研究;在实验室10kV交联聚乙烯电缆中间部位的电缆接头上制作进水缺陷,分别进行电缆接头S参数测量和时域脉冲反射实验;最后,分析和比较了电缆受潮接头的阻抗特性仿真和实验结果,证明了使用时域脉冲反射技术对受潮电缆中间接头进行受潮诊断的可行性和有效性。     

35 kV及以下XLPE电力电缆试验方法的研究

通过对交链聚乙烯（ＸＬＰＥ）电力电缆试品的工频、０．１Ｈｚ超低频和振荡３种击穿电压的平行比对试验研究,探讨能够有效发现、判别ＸＬＰＥ电力电缆运行故障隐患的试验方法,试验研究结果表明：振荡波电压试验能够有效地发现电力电缆及其附件的制造和安装质量缺陷,超低频电压试验能够有效地发现电力电缆及其附件绝缘树枝状早期劣化缺陷;工频电压试验是一种较好的方法,需进一步深入研究。     

Application of thermoelectric aging models to polymeric insulation in cable geometry

The life expressions of models of insulation aging are functions of temperature and field as well as material parameters. A methodology is presented that allows these models to be applied to a cable geometry in which there is a radial variation of both field and temperature. In this way material parameters can be extracted from cable data. The methodology is illustrated using one such model and the parameters deduced from cable failure distributions are compared with those obtained for thin films. This comparison allows conclusions to be drawn about how the aging process affects specimens of the same material with different volumes     

Ageing and reliability testing and monitoring of power cables:diagnosis for insulation systems: the ARTEMIS program

The ARTEMIS BRITE-EURAM program has been presented in this paper. Its main objective is to develop a diagnostic methodology to assess i) the susceptibility of polymeric cable insulation to electrical ageing; and ii) the state of the insulation at any chosen time in order to evaluate the remaining life-time of operating power cables. The ARTEMIS partners include cable manufacturers, material suppliers, electricity distributors and a number of universities throughout Europe     

The development of underjacket moisture barrier cable as a countermeasure against treeing

Materials have been developed to allow rapid commercialization of underjacket moisture barrier sheathed medium-voltage power cables. Plastic-coated aluminium and copper tapes meet the needs for a radial metallic moisture barrier. These tapes have outstanding initial adhesion to polyethylene, chlorinated polyethylene, or polyvinyl chloride jackets and excellent bond stability during thermal loading, temperature cycling, water aging, and exposure to elevated temperatures. Semiconductive water-swellable tapes have been developed which function as cushion (thermal expansion) layers and longitudinal water blocks. These tapes are commercially available from several sources. Commercially available hot melt adhesives are effective in sealing the overlap of the metallic moisture barrier and meet the criteria for adhesion and bond retention. These materials have been combined to produce a viable water impervious medium-voltage power cable. Underjacket moisture barrier cables have been commercially manufactured and have passed several key industry tests. The properties and installation characteristics of the cable are detailed     

交联电缆集群敷设载流量的数值计算

在人口稠密的大城市,电力通常通过直埋电力电缆集群来传输。电缆载流量是电缆设计和运行中的一个重要参数。IEC 60287标准给出了单一媒质即均匀土壤中电缆群稳态载流量的计算方法,并给出了有回填土的非单一媒质中电缆群的载流量修正计算方法。为给电缆工程的设计与运行提供科学依据,采用基于场路结合的有限差分法,提出了非单一媒质中电缆群的载流量数值计算方法,深入研究了不均匀土壤中的电缆载流量及其影响因素。计算结果表明,IEC外部热阻修正计算方法的计算精度与回填土热阻系数有关。回填土热阻系数较大时,IEC计算载流量显著偏低。     

Computation of PD calibration reflectograms in shielded power cable

The basis for computing PD calibration reflectograms in shielded power cable is presented. The computed reflectograms include the effects of cable attenuation, initial pulse width, cable length, and PD detection bandwidth. The authors have developed a program based on the algorithms presented in this paper which they are making freely available to the technical community.     

中低压交联电缆集群敷设载流量的计算

根据IEC60287标准计算了中低压电缆在不同集群敷设方式、环境温度及土壤热阻下恒定负荷的稳态载流量,分析温度、土壤热阻系数对复杂情况敷设电缆群载流量影响程度的结果表明:土壤热阻系数是埋地集群敷设电缆载流量的关键影响因素,实际应用中,选择合适的土壤组分是增加集群敷设电缆载流量的重要手段。     

乙丙橡胶在我国中高压电缆中的应用

简介了乙丙橡胶在国内外中高压电缆中应用的情况,论述了中高压乙丙橡胶电缆料的设计和生产的关键,以及国内自主开发的乙丙橡胶电缆料在中压橡胶绝缘电缆上的应用。     

Modeling the effects of distance in single-conductor power cables in a three-phase power system

Single-conductor power cables are widely used in cable lines in Armenia and provide greater current conduction and reliability than triple-conductor cables. In this paper, the optimal distance between single-conductor power cables in a three-phase power system for a given arrangement (horizontal in the plane or triangular) and ambient (ground) temperature are determined. The results for single-conductor cable arrangements are presented in graphical form.     

Chemical-moisture barrier cable-concept and practice

Cables with sheaths providing protection from chemicals and moisture have gained in popularity among many industrial and utility users in North America and Europe. These sheaths are used to protect low-, medium-, and high-voltage power cables as well as fiber-optic and instrumentation cables. This paper presents an overview of the theory, design, testing, and field experience for each type of cable as it pertains to chemical and moisture protection. Documentation is provided covering underground installations of chemical-moisture barrier cable in a large petrochemical manufacturing facility located on the Texas Gulf Coast     

直埋电力电缆温度场计算模型

研究了埋设于复杂土壤中的电力电缆在暂态和稳态情况下的温度场和载流量,用有限差分法离散传热方程,对电缆和土壤区域分别采用极坐标和直角坐标;为了加快计算速度,采用了不均匀网络。本模型适用于电力电缆稳态和短路或过载等暂态的温度场和载流量的计算。     

Assessment of underground cable ratings based on distributed temperature sensing

Numerous power utilities have installed advanced distributed temperature sensing (DTS) systems to measure the temperature of underground cables. This paper presents a general procedure for real-time assessment of underground cable ratings based on DTS. After the identification and location of hot spots on a cable, the cable installation data, load, and DTS-recorded temperature over a period of time are used to estimate soil thermal parameters and assess cable ratings under normal and overloading conditions. In order to accurately estimate soil thermal parameters, a combined technique of the finite-element method and gradient-based optimization is used. The technique was validated in the laboratory and applied to a rating assessment of a 230-kV/500-MVA cable circuit. The assessed continuous and emergency ratings are helpful in improving the operation of this circuit.     

我国发展直流海底电力电缆的前景

例举世界重要的海底电缆工程,表明其中大部分为直流海底电缆工程。叙述直流输电特点,着重以不同类型的直流和交流海缆载流量计算,证明直流海底电缆在输电容量、输电损耗和电缆线路长度限制方面显著优于交流海底电缆。肯定了我国发展直流海底电缆的必要性。有些运行条件下直流海底电缆会是优先的方案,甚至是唯一的选择。提出以发展直流交联聚乙烯(XLPE)海底电缆作为主要目标,并在比较不同类型海缆绝缘中的空间电荷对电场分布和电气绝缘性能影响和深入研究空间电荷积聚、抑制和移去机理基础上,积极研发抑制空间电荷积聚的XLPE绝缘料,作为关键技术突破,用于开发直流XLPE绝缘海底电缆,推进我国直流海底电力电缆的技术发展。     

A new era in cable designs and materials to resolve environmentalissues

In recent years, environmental issues have had a profound influence on power cable designs and materials used in cable construction. This paper addresses the issues concerned with the effects of cables on the environment, as well as the effects of environmental conditions on cable performance and reliability. Effects on the environment include release of toxic materials and contamination of ground water. Environmental effects on cables are related to the presence of moisture, chemicals, ions, oils or solvents. All such issues must be considered in the evolution of environmentally-safe cables. This also extends to the manufacturing processes for producing cable insulation, jacketing and sheathing materials, as well as the cable manufacturing process itself. New cable designs and materials have been developed to mitigate many of the more serious environmental issues now associated with cable applications. Such designs and associated materials are reviewed in this paper. Emphasis is placed on the safeguards protecting the environment and on extending cable life and performance. These safeguards include technological advances in insulation, shielding, jacketing and sheathing materials, as well as new cable designs that cable specifiers should take into consideration when properly selecting and applying power cables for petroleum and chemical plant installations. Other user concerns that include cable diameter, short-circuit withstand, mechanical performance, installation, splices and terminations are briefly reviewed as they relate to current cable technology