Quantities extracted from space-charge measurements as markers for insulation aging

The relation of space charge-derived quantities with aging stresses and time is discussed in this paper. Polyethylene-based materials, aged for different times under electrical and/or thermal stress, are subjected to space charge measurements. Quantities are derived, that is, the threshold for space charge accumulation and the apparent, trap-controlled mobility, obtained by the threshold and the depolarisation characteristics, respectively, which show time variations depending on the level of applied stress and aging time, i.e. on the extent of degradation. This indicates that such quantities can be considered as aging markers useful for the diagnosis of bulk degradation in insulation systems aged under electrical field, dc or ac, and temperature.     

Digital recording techniques for electrical insulation measurements

The problems of measuring the characteristics of transient voltage and current waveforms occurring in high-voltage power systems are discussed, and the analog recorders that have been used in the past are reviewed. The theory of operation of digital recorders is described, and sources of recording errors are examined. Applications of digital oscilloscopes to measuring switching surges and partial discharges and to high-voltage impulse testing are discussed     

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     

直埋电（光）缆如何用屏蔽线高效防雷

对光缆通信线路受外力的影响,产生多发性故障的原因进行了分析,并提出了预防措施和方法,使光纤通信故障不断减少,确保通信畅通。     

Experience with return voltage measurements for assessing insulation conditions in service-aged transformers

This paper describes the investigation of the insulation condition of a number of power and distribution type transformers of different manufacturing dates and with different operating histories. Return voltage measurements were conducted for these transformers. Effects of moisture and aging on the oil-paper insulation of these transformers were investigated and results are presented in this paper. Moisture in oil samples at known temperature was measured for these transformers. Previously accelerated aging experiments were performed on paper wrapped insulated conductors in different environments over a temperature range of 115 to 145/spl deg/C. Results from the measurements on transformers are compared with those of the accelerated aged samples and are described in this paper.     

The use of partial discharge measurements to assess the conditionof rotating machine insulation

This article reviews some of the recent improvements in measurement technology that have enabled on-line PD testing to be applied to a significant percentage of high voltage motors and generators in use in North America today     

Deriving an equivalent circuit of transformers insulation for understanding the dielectric response measurements

Preventive diagnosis and maintenance of transformers have become more and more popular in recent times in order to improve the reliability of electric power systems. Dielectric testing techniques such as return voltage measurement (RVM) and polarization-depolarization current (PDC) measurement are being investigated as potential tools for condition assessment of transformer insulation. A better understanding and analysis of the dielectric test results are only possible with a clear understanding of the physical behavior of the insulation system in response to moisture and aging. A circuit model, which describes the dielectric behavior of the transformer's main insulation system, has been parameterized in this paper. The values of the parameters of the model have been identified from the dielectric tests. A correlation has been developed between the physical condition of the insulation and the equivalent model parameters that enable a clear and transparent interpretation of the dielectric test results.     

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     

Advanced PD inference in on-field measurements. II. Identification of defects in solid insulation systems

Results of investigations performed to evaluate the effectiveness of a new inference method for the diagnosis of solid insulation systems, based on partial discharge (PD) measurements, are reported in this paper. Signal separation, noise recognition, and PD source identification are the main features of the proposed inference method. Techniques for signal separation and automatic noise rejection are reported in the 1st part of this paper, while the problem of the identification of PD phenomena, occurring in defects of insulation systems, is approached in this 2nd part. The identification is based on fuzzy logic and enables the recognition of PD generated from different basic sources, such as internal, surface and corona discharges. It is shown that the different source typologies can be identified by means of fuzzy rules applied to a selection of parameters derived from PD-pulse phase and amplitude distribution analysis, once PD phenomena have been clustered in homogeneous class through a fuzzy algorithm based on PD-pulse shape. The proposed identification procedure is finally applied to rotating machines and cables, affected by insulation defects, showing promising on-field applications.     

Current practice in space charge and polarization profile measurements using thermal techniques

Thermal techniques for probing space charge and electric field distributions in dielectric materials became available approximately 30 years ago. The techniques have reached maturity and they have been employed not only for the primary purpose of electric field or polarization profiling, but also in a wide range of problems posed by materials research. The present survey provides an overview of the historical development, the experimental implementation of the different techniques, the theoretical foundation, methods for the data analysis and a comparison of thermal and acoustic techniques. The thermal wave technique LIMM is used as an example among the thermal techniques, for a discussion of data analysis techniques and for the spatial resolution that can be achieved with thermal wave techniques. A tour d'horizon is provided through recent applications of thermal techniques, in order to demonstrate their capabilities for dielectric material characterisation.     

输电线路分段地线感应取能方法研究

利用导地互感公式推导了不同相线电流情况下地线损耗功率,在此基础上提出了一种可应用于分段地线网络的地线取能方法,并基于所提方法设计了取能设备。该取电装置具有输入动态范围大、转换效率高、抗干扰能力强的特点。在导线负荷满足要求的情况下该装置可以替代光伏电源实现对在线监测设备的稳定供电。     

Aging diagnosis of insulation systems by PD measurements.Extraction of partial discharge features in electrical treeing

The charge height values associated with PD measured during electrical tree inception and growth are processed according to the Weibull distribution. Test arrangements, based on the needle-plane electrode system, consider specimens having either a cavity at the tip or an intimate contact with insulation. It is shown that the Weibull-function parameters have close relation to discharges occurring in cavity and tree channels, and that an indication of inception of electrical trees can be obtained     

应用电缆温度实时监测系统防范电缆火灾

目前防范电缆火灾措施有缺陷 ,这些措施多在火情初期或后期时才查知和发挥作用。为了在火灾隐患的潜伏期早发现从而采取积极有效的防火措施 ,开发了电缆及电缆接头温度监测 (报警 )系统。该系统可在机房、变电站、电缆隧道等处实施电缆温度实时监测 ,防范电缆火灾 。     

Statistical pattern analysis of partial discharge measurements for quality assessment of insulation systems in high-voltage electrical machinery

In this paper, we present a new statistical analysis method of phase-resolved partial discharge (PD) measurements for the quality assessment of electrical insulation in high-voltage machinery. The method is based on a supervised classification approach which utilizes histogram similarity analysis. The motivation for choosing histogram similarity analysis is twofold. First, the phase-resolved PD measurement itself is, in fact, a two-dimensional histogram. Therefore, a histogram-matching-based approach suits the very nature of the data. Second, histogram similarity analysis combines the typical statistical parameters, used in PD analysis, in a statistically powerful and rigorous way. In our study, we utilize various histogram types and similarity analysis, including correlation, chi-square, and Kolmogorov-Smirnov tests. Further, we propose a postprocessing method to quantify the accuracy of classification results which enables the user to make soft decisions. Our experimental study on laboratory samples demonstrates that the method shows strong potential in detection and classification of insulation defects. The results from our study suggest that the proposed method provides a powerful, general, and mathematically simple approach to the analysis of phase-resolved PD measurements.     

Comparison of magnetic flux density meter responses over a databaseof residential measurements

Fourteen possible types of magnetic flux density meters based on the Faraday induction principle have been mathematically simulated. The different readings obtained from each type when the magnetic flux density is more complex than the ideal case of a single frequency (60 Hz) with linear polarization are shown. Using a real database of residential flux densities from 17 homes, it is shown that the presence of harmonics and elliptical polarization can result in significant deviations in readings between meter types. The highest variations from the total RMS (root mean square) flux density are found with broadband meters that have derivative responses or corrected peak detectors     

高压电缆防治白蚁蛀蚀措施初探

近年来由于白蚁蛀蚀电缆引起故障和造成缺陷事例有不断上升的趋势,为此广州分公司组织开展了高压电缆防止白蚁蛀蚀的研究。通过与专业科研机构合作并结合广州地区高压电缆的安装情况,对多个专题进行了研究,经过调研和实验室试验初步得出一些结论,可为生产和进一步研究高压电缆防白蚁提供参考。     

我国户外隔离开关从超高压向特高压跨越

我国于1966年为我国第一条330KV输电线路(刘天关线)自主研制成功GW7-330型户外隔离开关,揭开了我国超高压隔离开关发展史的第一页,在覆盖陕、甘、宁、青四省(区)的西北330KV电网建设中发挥了重要作用.20世纪80年代,开创了我国自主设计独立制造550KV变电站.