高压交流电缆用交联聚乙烯绝缘料性能对比实验研究

中国高电压等级交流电缆用交联聚乙烯（XPLE）绝缘料研发较晚,目前国产220 kV电压等级绝缘料暂未获得工程应用。以3种国内外高压电缆XLPE绝缘料为研究对象,对比分析绝缘料热压试样的工频击穿场强、介电常数、介质损耗正切、熔融和结晶性能、拉伸强度、断裂伸长率、微观形貌和交联度等参数。实验测试结果表明：国产XLPE绝缘料的宏观性能参数已经和进口XLPE绝缘料相差不大,甚至国产绝缘料试样的击穿场强和力学性能参数优于进口X1#试样,但同时也能够发现国产绝缘料的不足之处,例如击穿场强的稳定性较差、介质损耗角正切值偏大等。研究结论可为国产电缆绝缘料的研发与性能提升提供数据支撑。     

The possibilities offered by use of solid insulation in complete switching gears and cross-linked polyethylene insulation under direct and alternating current

The prospects for use of energy cables with cross-linked polyethylene insulation (CLPE) and switching gears with solid insulation under direct and alternating current are considered. The main developments in the work of enterprises manufacturing cable products are listed, and their main characteristics are given. The advantages of cables lines with cross-linked polyethylene insulation over cable lines with paper–oil insulation are described: increased capacity, high permissible insulation temperature, smaller cable bend radius, smaller weight–size parameters, increased service life, the possibility of being laid at low temperatures, and high environmental characteristics. The global experience and main problems of application of cross-linked polyethylene insulation cables under direct high-voltage current are analyzed. The variants of performance of the insulation and structure of 6–35 kV switching gears of different producers are studied. Some functions of switching gear, typical structures, and equipment structure are listed, and the main test modes for insulation of separated section and units of the switching gears are described. Different types of solid insulation of complete switching gears (CSGs) of medium voltage are compared: with and without a grounded shield on the surface. Reduced weight–size parameters and increased electrical safety are identified as advantages of the structure with a shield. Data on perspective Russian development in the area of complete switching gears and solid insulation are presented, and the conclusions regarding their main advantages are drawn. The basic functional of the system of control and monitoring by new-generation switching gear of the is offered.     

Effects of voltage impulses on extruded dielectric cable life

Laboratory tests were performed to investigate the effects of lightning and thumping impulses on the performance of various 15 kV cable designs. The cable designs were aged in the laboratory using an accelerated water treeing test. Some samples were subjected to lightning impulses, some were subjected to thumping impulses, and some were aged without impulses applied. The impulse effects were evaluated using time to failure data, AC breakdown data, and impulse breakdown data. The results show that lightning or thumping impulses do not affect cable AC or impulse breakdown strength. There is also no visual difference between wafers taken from impulsed and control samples. However, there is a strong indication that lightning impulses can reduce cable life. Almost all the aging failures occurred while the cables were warm. No failures occurred during the impulse application. It is also shown that increased cable wall thickness extends cable life for the tree-resistant high-molecular-weight insulation material tested, but not for the crosslinked polyethylene insulation material tested     

Evaluation of service aged 35 kV TR-XLPE URD cables

This paper provides information on the aging of URD power cable insulated with a tree-retardant crosslinked polyethylene (TR-XLPE) compound, installed in a typical utility environment, Numerous evaluations were performed on samples of power cables aged up to 7 years in-service. AC and impulse voltage breakdown data are compared with data for similar 35 kV ethylene propylene rubber (EPR) and crosslinked polyethylene (XLPE) insulated cables removed from the same utility system. The data show that, to date, the rate of degradation of TR-XLPE cables is less than that of the EPR and XLPE insulated cables. Extrapolation of the data, assuming the same rate, indicates TR-XLPE cable will have the longest life     

Space charge measurements in polymeric HV insulation materials

This paper reports on a study using the laser induced pressure propagation (LIPP) method to measure the space charge characteristics in bulk crosslinked polyethylene (XLPE) insulation under dc electric stress. Particular attention has been given to the quantitative appraisal of calibration parameters, and the resultant estimations of space charge and electric stress distributions. A method is described for analyzing the measured raw data from ramp voltage and aging tests to give an estimate of charge and stress without resorting to a complicated mathematical exercise. The consequence of stress enhancement due to the trapped charge on the life of the insulation is estimated using the empirical inverse law. Using analysis of variance and a multivariate analysis technique, the effects of treatment and type of XLPE on the space charge characteristics are also discussed     

水中敷设电缆载流量的实验和分析

为了研究水中敷设电缆的载流量特性,设计了110 kV交联聚乙烯单芯电缆水中敷设、空气中敷设2种条件下的阶跃电流暂态温升实验.对实验数据进行分析发现:相同电流下,稳态时,水中敷设电缆的线芯温度要比空气中敷设电缆的线芯温度低30%以上;相同负荷特性时,水中敷设的电缆可以提高载流量50%以上.     

The influence of the water on water absorption and density of XLPEcable insulation

This paper presents the results of a continuing investigation into effect of water on water absorption and density of crosslinked polyethylene (XLPE). The experimental set up was made for the following XLPE cable insulations: steam and dry cured with water tree retardant crosslinked polyethylene (TR-XLPE) and without water tree retardant crosslinked polyethylene (natural XLPE). During tests, the tap water was injected (1) into the cable conductor with cable ends closed, (2) into the cable conductor with cable ends opened, and (3) into the metallic screen with cable ends opened. The XLPE cable insulation together with the water present in the cable was subjected to electrical stress and heating. The results were analyzed theoretically and experimentally. The aim of this paper is to present the results of the influence of the water on water absorption and density of various kinds of XLPE cable insulation in different service conditions     

Comparative laboratory evaluation of TR-XLPE and XLPE cables with Super-smooth conductor shields

This paper provides data on four commercial tree retardant crosslinked polyethylene (TR-XLPE) and one cross-linked polyethylene (XLPE) insulated 15 kV cables supplied by three manufacturers. The cables have "super-smooth" conductor shields and "extra-clean" insulation and insulation shields. AC and impulse voltage breakdown and selected other characterization data are presented for cables that were aged immersed in room temperature water (15-30/spl deg/C) up to 24 months of a planned 48 months aging program. The five cables have high ac voltage breakdown strength, three of the TR-XLPE cables, actually increased in breakdown strength during aging. The one TR-XLPE cable that had the lowest ac voltage breakdown had vented trees at the insulation shield and high dissipation factor, which the other cables did not have. The impulse voltage breakdown strength of all cables decreased during aging; the cable with the lowest ac voltage breakdown also has the lowest impulse voltage breakdown. The dissimilar performance of the TR-XLPE cables and the excellent performance of the XLPE cable indicates evaluations at longer times are required to differentiate between modern TR-XLPE and XLPE insulated cables.     

Study on the dielectric characteristics of DC XLPE cables

The DC characteristics of XLPE (crosslinked polyethylene) power cables were investigated. Cables with an insulation thickness of 2.5 mm, 9 mm, and 13 mm using either XLPE or conductive-inorganic-filled XLPE (XL-A) were manufactured, and four kinds of breakdown tests (DC, polarity reversal, impulse, and superposing opposite polarity impulse on DC prestress) were performed. A 250 kV, XL-A cable (20 mm thickness) was designed and manufactured using the results. The test results show that the XL-A cable possesses much better DC breakdown characteristics than the XLPE cable and is adequate for use in DC cables     

Definition of the remaining life of power-transmission lines with cross-linked polyethylene insulation

XLPE-insulated cables and wires are becoming more widespread. For this reason, it is becoming necessary to control the state of insulation over its total operating life. Online monitoring of the effects on the insulation and determination of its remaining life becomes possible using modern equipment. In this paper, a method of determining the remaining lifetime of the cross-linked polyethylene insulation of the powertransmission line is presented. An insulation-aging model developed at the previous stage of the research was used. It is proposed to control the destructive effects on the insulation and calculate the remaining life based on the obtained data. The results of the research showed that the probability of failure is subject to the normal character of distribution (Gaussian distribution) as the insulation in the process of operation is exposed to a large number of effects (partial discharges, thermal actions, effect of the environmental factors, etc.). The remaining lifetime is defined as a function of inverse failure probability. The proposed method can be used to develop a set of devices for determining the remaining life of polyethylene insulation.     

高压XLPE电缆绝缘多参数在线监测

建立了在交流电压作用下高压交联聚乙烯(XLPE)电缆绝缘的参数模型,并分析了电缆绝缘劣化时绝缘参数的外在表现.提出通过监测XLPE电缆的工作绝缘电阻、等值电容、介质损耗因数及各参数的变化趋势来综合评定电缆的绝缘状况.并分析了该方法的有效性及合理性.设计了高压XLPE电缆在线监测装置.在数据处理方面,采用基于LM(Levenberg-Marquardt)算法的非线性最小二乘拟合法对采样信号进行拟合,将信号进行快速傅里叶变换得到的谐波分析结果作为LM算法的迭代初值,并利用拟合结果计算出电缆绝缘的被监测参数.仿真分析表明,该算法收敛速度快、精度高,能很好地抑制电网频率波动、直流分量以及谐波含量对被监测参数的影响.     

The chemistry of polyethylene insulation

The molecular structure of polyethylene and its copolymers is discussed, with particular attention to its effect on thermal and mechanical properties. The synthesis of polymers of various densities and of the copolymers is examined. The effects of changes in average molecular weight and of molecular weight distribution are considered. Vinyl-acetate-modified polyethylene, wire and cable coating, antioxidants and carbon black fillers, crosslinked wire insulation, peroxide crosslinked polyethylene, and water curable compounds are discussed     

Effect of water on aging of XLPE cable insulation

Cables as elements of power distribution system have great influence on its reliable service and overall planning requirements. During last years, crosslinked polyethylene (XLPE) cables have been more and more used in power systems. This paper presents the results of an investigation of changing of (XLPE) cables insulation breakdown stress (AC BDS) due to water absorption. The paper deals with AC BDS of the following kinds of XLPE cable insulations: steam and dry cured with water tree retardant crosslinked polyethylene (TR-XLPE) and non-tree retardant crosslinked polyethylene (XLPE). During tests, the tap water was injected into, (1) conductor with cable ends closed; (2) into cable conductor with ends opened; and (3) into metallic screen with cable ends opened. The presence of water in XLPE cables was subjected to electrical stress and heating. AC BDS tests were performed as a function of aging time and water content in the cable insulation at different aging temperatures. Also, in this investigation, tests with the changing of AC BDS in the radial direction of unaged and aged XLPE cable insulations were carried out.     

EPRI report-characterization of cable insulation materials bydynamic mechanical spectroscopy

A project that is part of a broad effort to apply nonelectrical diagnostics to the study of aging-induced changes in solid dielectric cables is described. The technique of dynamic mechanical spectroscopy is explained. The goal of the work described was to determine whether aging in high-molecular-weight polyethylene (HMWPE) or crosslinked polyethylene (XLPE) insulated distribution cable insulation could be detected by solid-state rheological measurements. Insulation from seven HMWPE and five XLPE cables were studied. The results and their interpretation are summarized. They suggest that a more detailed study of a number of service-aged and laboratory aged XLPE's, tree-resistant XLPEs, and EPR would be highly beneficial     

Extending the service life of 15 kV polyethylene URD cable usingsilicone liquid

The authors describe methods and materials used to extend the useful life of extruded polyethylene insulated cables rated at 15 kV that have developed electrochemical trees in the insulation of sufficient severity to cause service failures. Earlier rehabilitation methods treated extruded dielectric cables with both gases and insulating liquids. This new method fills the cable and impregnates the insulation with a silicone liquid. This liquid, which is reactive, significantly improves the voltage breakdown strength of the cables, which had been reduced by electrochemical trees, and extends the useful service life of the cable. A review of the criteria used to develop the silicone liquid for this application and the methodology used to inject it into the cable are presented. An assessment of the costs for this life extension indicates a significantly lower cost than conventional cable replacement with little disturbance to the service and property of the customer     

Evaluation of materials for WTR-insulated power cables

In order to improve the resistance to water treeing of standard crosslinked polyethylene (XLPE) insulation used in medium voltage power cables, a number of materials were selected and studied that represent different water tree growth prevention strategies: (a) using materials with crystallinity and morphology different from that of XLPE, or (b) using additives modifying the interaction between water and materials. Two laboratory procedures were adopted that assess the water tree resistance performance of the materials through different criteria: one based on divergent field geometry (CNRS) and another based on uniform field geometry (Pirelli). Both tests are shown to be complementary in their prediction of the performance of the selected water tree resistant materials. The work reveals a specific additive that greatly increases the water tree resistance performance of the insulation in different polymeric matrices     

Some factors for the space charge formation in polyethylene

Information on space-charge behavior in thick insulated samples aids in understanding the dc characteristics of polymer-insulated dc cables. The pulsed electroacoustic method is used to investigate several space charge formation factors in 2 mm-thick polyethylene (PE). The following results were obtained. For measurement factors: (1) A polymeric semiconducting electrode provides a more accurate measurement than does a metal electrode as a result of better matching of acoustic impedance with PE. (2) Within a dc electrical stress range of several tens kV/mm, the space charge distributions under and after dc voltage application are almost the same; this is due to a comparatively long time of space-charge decay. (3) The space-charge distribution of a plate sample agrees with that of a cable sample having the same insulation thickness. For insulating material factors: (1) The amount of space charge in crosslinked polyethylene (XLPE) is much larger than that in low-density PE (base of XLPE). The space charge of XLPE continues to increase even after dc voltage application (24 h); that of LDPE reaches equilibrium with a few hours. (2) The aforementioned space charge difference between XLPE and LDPE is assumed to be caused by ionic impurities in XLPE, not by the additives themselves (acetophenon and cumylalcohol as byproducts of cross linking and antioxidant).     

The world's first use of 500 kV XLPE insulated aluminium sheathedpower cables at the Shimogo and Imaichi power stations

The world's first practical applications of 500 kV XLPE (cross-linked polyethylene) cables took place in 1988 at the Shimogo power station of the Electric Power Development Co. Ltd., and the Imaichi power station of the Tokyo Electric Power Co. Inc.. Research and development work on the cables had been conducted since 1982. Efforts were concentrated on quality control to remove contaminants from the insulation and to extrude the very thick-walled insulation without any defects. Insulation performance tests, including long-term aging, confirmed that the 500 kV XLPE cables and the terminations were highly reliable with superior initial and long-term performance. The installation was completed successfully, and the cables are now in satisfactory operation at both power stations. The cable routes, design of the cable and termination, cable manufacture, results of the insulation performance tests, installation work, and site test are discussed