Aging of polymeric insulating materials in power cables

More than 160 years of history go with the use of polymers in the cable industry. Polyethylene of low and high density and crosslinked polyethylene gradually succeeded paper and polyvinylchloride. This review discusses some aspects of the aging processes of polyethylene under working conditions. Electrical and water treeing are considered, dependent upon the morphology and the induced characteristics of the insulating material     

Evaluation of motor power cables for PWM AC drives

Three-phase power cables installed between the inverter and motor of AC motor drive systems have been mostly ignored in the years since AC drives have become widely accepted in industrial applications. However, power cable characteristics have become quite critical with the advent of faster inverter switching times, which have decreased by a factor of perhaps 20:1 in the last ten years. This paper describes the present areas of concern with regard to power cabling, as well as a test program to quantitatively evaluate power cable-related remedies for these problematic areas. A relative ranking of test results is developed comparing the eight power cable types tested. Cable connector considerations are examined, together with interconnection of the cable shield, or sheath, and the NEC ground circuits are discussed in light of the test results and recommendations presented. Power cable voltage ratings are discussed and recommendations made. A final cable total performance comparison, including installation factors, summarizes the paper     

Evaluation of methods for discrimination of energized underground power cables

The maintenance and repair of underground cable power networks often requires the discrimination of energized cables among a group of unenergized ones. Presently, an invasive detection method is performed which requires utility personnel to puncture the protective cable shielding, creating a potentially hazardous situation. This paper presents a noninvasive approach for energized cable detection based on the electrically induced acoustic waves inside of the cable. The influence of background electric fields on the performance of this approach is studied. In addition, the use of a fiber optic acoustic sensor would significantly increase the safety of the detection procedure, borrowing on the intrinsic electrically insulating properties of optical fibers (i.e. dielectric, immunity to electromagnetic interference, etc.). Feasibility studies and preliminary experiments were performed using a fiber Fabry-Pérot interferometric acoustic sensor. The performance of the fiber optic sensor is compared with that of a piezoelectric accelerometer. A detailed analysis of the test results is included. Recommendations are given for correct interpretation of test results based on the specifics of a power system and sensor type.     

ESCA analysis of semiconducting layer materials in XLPE power cables

This paper describes an application of ESCA analysis to semiconducting materials in XLPE power cables in terms of the oxygen ratio (integrated intensity of oxygen spectrum/integrated intensity of carbon spectrum). Analyzed materials were carbon black, an additive mixed into semiconducting materials, and several semiconducting materials treated in various cross‐linking conditions. It was found that the additive increases the oxygen ratio of semiconducting materials as well as does the cross‐linking treatment. The higher the oxygen ratio of the semiconducting materials, the smaller is the average lamellar angle in the XLPE insulation at the semiconducting interface. The angle is thought to be a parameter which expresses the hyperstructure of polymer insulation and smaller angles correspond to a better state of the semiconducting interface in XLPE power cables. © 1998 Scripta Technica, Electr Eng Jpn, 126(2): 15–22, 1999     

35kV以下电力电缆户内终端用热缩材料研制

本文介绍了 3 5 k V以下电力电缆户内终端用 PE/ CPE共混热收缩材料的研制过程 ,以及 PE/ CPE配比 ,Al( OH) 3 ,辐射剂量等对共混材料的力学性能 ,阻燃性能的影响规律。制得了氧指数 OI大于 2 7,拉断强度 TS>1 0 MPa,绝缘电阻率 ρv>1 0 1 3 Ω· cm,击穿电压 >2 0k V/ m m的户内终端用阻燃热收缩材料     

发电厂电缆防火措施探讨

做好发电厂内电缆防火、防止电缆火灾引发重大事故是一个实际而又重大的课题。为此,针对电厂电缆火灾事故时有发生的情况,简述了目前发电厂电缆防火的主要措施,并以广东省某电厂9号机组电缆事故的防范为例,详细介绍了其电缆防火的措施,这些措施对其它电厂有一定的参考价值。     

Insulating materials evaluation for Cold Dielectric superconducting cables

The realisation of the so-called "cold dielectric" cable, where the insulation is kept at a cryogenic temperature, entails the choice of an optimised insulation system, with properties that are the best compromise between physical-electrical characteristics and design requirements. To this purpose, a specific study was planned to qualify different materials. On the basis of literature results, mostly carried out at liquid helium temperature, polypropylene laminate (PPL), paper, high-density polyethylene (HDPE) fiber and ethylene-propylene rubber (EPR) were chosen as potential candidates for the final use in liquid nitrogen. Electrical properties of materials were evaluated and compared by means of different models. Flat and cylindrical models were used to characterise the intrinsic properties of materials and determine the impact of the technological processes, respectively. Short term and long term tests were carried out at liquid nitrogen temperature and at different absolute pressures for the evaluation of electrical endurance. As far as short term tests are concerned, AC and lightning impulse (LI) breakdown step tests were performed. Long term tests were carried out under AC field; furthermore, power factor and partial discharge measurements were made to evaluate the impregnation process. The results of the whole testing procedure indicate that PPL shows the best behaviour for the application at cryogenic temperature in a superconducting cable.     

交联电力电缆故障点的定位

本文详细介绍了用于检测交联电力电缆击穿故障和局部放电定位的方法和使用的仪器 ,以及测试线路的改进     

核电站电缆的性能及测试

本文介绍了 K3类核电站电缆的主要性能及测试 ,产品包括 6 .6 k V,10 0 0 V电力电缆 ;10 0 0 V控制电缆 ;测量电缆等     

Advanced solution for on-site diagnosis of distribution power cables

This paper describes important aspects of partial discharge (PD) diagnostics of distribution power cables. PD parameter were discussed under consideration of attenuation and dispersive effects of cable characteristics. Field experiences with PD diagnosis on paper insulated cables (PILC) and cables with cross linked polyethylen insulation (XLPE) by energizing with Damped AC Voltage demonstrate relevant demands and the effective outcome for asset management decision support. The main difficulty is to evaluate the risc of PD occurrences on the reliability of the cable system. If an sufficient amount of PD diagnostic data for the cable components is available statistical methods can be used for determing threshold levels and relevant condition indexes for the asset management.     

Insulation coordination of MV power cables

In medium voltage power cables, the concept of cost/reliability has been current since the end of the 1980s when the Brazilian Standards introduced ethylene-propylene-rubber (EPR) insulated cables, with different thicknesses of insulation for conventional cables and for those with blocked conductors or with water tightness constructions. However, despite the benefits obtainable by use of such cables, they have had limited use by electrical power utilities; perhaps because the concept has not become widely recognized. This paper intends to clarify and submit a new approach for design of the dielectric system of medium voltage cables, for use in underground and insulated overhead distribution feeders. Theoretical aspects of sizing the dielectric system, by means of coordinating the insulation, and also using reliability parameters, is dealt with in the paper. Results of practical applications are also presented and discussed     

Thermal modeling of portable power cables

The US Bureau of Mines investigated the performance of portable power cables under time-varying load conditions. This research had a twofold purpose: (1) to define the thermal characteristics of electrically overloaded trailing cables; and (2) to construct a thermal model for cables to predict cable temperature rises resulting from load currents. Several tasks were undertaken in support of these goals during the three-year research effort. Overload tests ranging from 2 to 12 times rated ampacity were conducted in the Pittsburgh Research Center's Mine Electrical Laboratory. A thermal model of energized type G-GC trailing cables was constructed based upon empirical data from the US Bureau of Mines load tests. This model was then incorporated into an interactive computer program that can assist designers and approvers of mining machines in selecting the appropriate size trailing cable. This program can be the basis for a cable protection system which ensures that cables are not the source of fires, ignitions, burns, or explosions underground     

Retrofitting-new high voltage XLPE cables substitutingpaper-insulated power cables in steel pipes

Many utilities still have paper-insulated pipe type cables in service. In the near future they may have to replace some of these systems due to local increases in electric power demand or aged cable insulation. In many cases the steel pipes are well protected against corrosion and thus suitable for further use. For retrofitting in such installations, XLPE-insulated cables offer several advantages. Felten & Guilleaume Energietechnik AG has developed a new three-core XLPE-insulated 64/110 kV cable with reduced insulation thickness (10 mm), that can be pulled into a pipe. In co-operation with VEW ENERGIE AG, the cable performance is being investigated in a field test, that started in October 1996. This long-term loading cycle test will last for three years. The test voltage, applied between conductor and earth, amounts to 127 kV. The temperature is measured with the help of an optical-fiber measurement system. This device is computer controlled and works as a remote monitoring system     

阻水型电力电缆的主要结构和关键工艺

阻水型电力电缆作为电线电缆行业的一个新品种,正随着经济的发展、技术的成熟而得到推广应用。该文就阻水电力电缆的结构设计和工艺控制提出一些看法。     

High voltage insulation for power cables utilizing high temperaturesuperconductivity

It is worth noting that, with a few exceptions, the efforts to develop dielectric systems, especially for the LTD superconducting cables, are lagging behind the intense efforts to develop more efficient HT superconducting materials, tapes, and conductors. The results presented here and reported in the literature confirm that lifetime is usually greater for cryogenic insulation, and thus the impulse and switching surge breakdown strengths may be a limiting factor in determining the operating stress of such insulation     

电力电缆讲座 第一讲 电缆的结构和特性(上)

我国城市电网中 ,电力电缆的应用越来越广泛。近年来 ,一些大中城市加快了城网建设改造的步伐 ,在 1 1 0 k V及以下供配电系统大力建设和发展电缆网 ,特别是在城市中心区段 ,结合市政改造积极采用电缆供电 ,并有条件地进行“电线入地”。随着城网电缆化比例的提高 ,城市供配电网的供电可靠性也相应提高了。为此 ,本刊特请作者撰写《电力电缆》讲座 ,重点介绍 1 1 0 k V及以下电缆应用技术方面的一些有关问题。其中包括电缆的结构和特性、电缆敷设、接头安装、电缆试验及故障测寻和电缆运行管理等专题。供从事供配电电缆规划设计、施工安装及运行检修的人员参考。全文共五讲 ,分六期刊出。     

Classification of superconducting cables of power purpose

Classification of low-temperature and high-temperature superconducting cables of direct and alternating current for power purposes based on the traditional and prospective implementation is presented. Results of designing multicore superconducting cables with localized magnetic field, providing maximal critical current density, reducing consumption of superconducting material, cold fluid, and energy losses in cables are reported.     

Interfacial microstructure and withstand voltage of polyethylene for power cables

In order to increase the electrical breakdown strength and treeing inception voltage of cross-linked polyethylene (XLPE) insulated power cable, surfactant in combination with titanate coupling agent, as an additive, has been mixed with the semiconducting layer, which is surrounded by polyethylene insulation, to chemically improve the dielectric properties of polyethylene interface. By means of infrared and X-ray diffraction spectra analyses, a change in the crystalline orientation angle and the density of polyethylene is observed inside the improved polyethylene interfacial layer. Additionally, it is assumed that a thin diffusion layer is formed, that results in a decrease in the electric field stress on the polyethylene interface and then an increase in the withstand voltage of polyethylene.     

Development of a partial discharge location method for power cables

Insulation deterioration of power cables can be measured by the method of partial discharge. If a large partial discharge is detected in a cable, the cable is considered to be defective and a partial discharge is located to find the position of the defect. However, partial discharge location methods are generally disadvantageous in that they require much skill for operation and have inferior sensitivity and accuracy. To solve these problems, the authors developed a locating method using two-phase cable and an automatic partial discharge locator which automatically localizes the generating site of discharge immediately after making partial discharge measurement by simple operations. Field measurements are made on SL (separately lead-covered) cables and other cables with the locator to test its accuracy and reliability, and it was found that the device is effective and useful.     

Development of water pipe cooling system for power cables intunnels

A full-size test line was constructed to study the water pipe cooling system for a bulk-power transmission line installed in a tunnel. Based on the test data and their analysis, a technique for designing the system has been established. The results have indicated an effective layout of the cooling pipes in the tunnel, and have validated the accuracy of the computer models to determine thermal characteristics of the tunnel system. An efficient control method to operate the cooling system according to the load changes of the cables was developed. The chosen layout is shown to be more effective than the dispersed layout because it accelerates the air convection and makes the air temperature more uniform. Furthermore, the thermal convection resistance between the tunnel wall and the air is reduced. It was also verified that the air temperature distribution along the vertical shaft could be predicted by thermal convection analysis. This cooling system is scheduled to be applied to a 154 kV power cable line in 1990