变压器现场局部放电缺陷查寻及原因分析

局部放电测量技术作为检验电气设备内部绝缘好坏的有效手段得到越来越普遍的应用。采用“多端测量 ,多端校正”及电气一超声联合测试 ,可准确发现并确定现场安装后的电力变压器内部存在的缺陷及其位置。试验结果表明 ,在现场进行电力变压器的局部放电试验 ,对提高安装质量 ,防止设备损坏及保证电网的安全运行将会起到积极的作用。     

GA747Ⅱ剑杆织机织疵的产生原因和控制

重点介绍GA747Ⅱ型剑杆织机织造坯布常见的疵点，通过详细分析并结合生产实践，总结出相应的防治措施，把织物疵点控制在最低水平，以生产出高质量的产品，获得较好的经济效益。     

Characterization and comprehension of corona partial discharge in air under power frequency to very low frequency voltage

For the partial discharge test of electrical equipment with large capacitance, the use of lowfrequency voltage instead of power frequency voltage can effectively reduce the capacity requirements of test power supply. However, the validity of PD test under low frequency voltage needs to be evaluated. In order to investigate the influence of voltage frequency on corona discharge in the air, the discharge test of the tip-plate electrode under the frequency from 50 to 0.1 Hz is carried out based on the impulse current method. The results show that some of the main features of corona under low frequency do not change. The magnitude of discharge in a positive half cycle is obviously larger than that in a negative cycle. The magnitude of discharge and interval in positive cycle are random, while that in negative cycle are regular. With the decrease of frequency, the inception voltage increases. The variation trend of maximum and average magnitude and repetition rate of the discharge in positive and negative half cycle with the variation of voltage frequency and magnitude is demonstrated, with discussion and interpretation from the aspects of space charge transportation, effective discharge time and transition of discharge modes. There is an obvious difference in the phase resolved pattern of partial discharge and characteristic parameters of discharge patterns between power and low frequency. The experimental results can be the reference for mode identification of partial discharge under low frequency tests. The trend of the measured parameters with the variation of frequency provides more information about the insulation defect than traditional measurements under a single frequency (usually 50 Hz). Also it helps to understand the mechanism of corona discharge with an explanation of the characteristics under different frequencies.     

基于单片机的电力电缆绝缘故障在线监测系统的设计与构建

电力电缆在运行过程中,必然要出现绝缘老化,甚至引发绝缘击穿,导致供电线路的突发停电事故。绝缘老化的本质是材料性能发生不可逆转的改变,影响老化的因素一般涉及热、电、机械与环境等方面。在线监测通过全系统多测点数据联合分析计算电缆绝缘状况,综合确定漏电或绝缘降低的情况和故障点位置,因而具有重要价值。文章为此主要介绍基于C8051单片机的电力电缆在线监测系统的组成、监测功能和监测原理。     

空间电荷对油纸绝缘击穿和沿面闪络的影响

换流变压器是直流输电工程的核心设备之一,其结构和工作状况比传统交流变压器更为复杂,需要对其绝缘系统进行更深入的研究.本文针对换流变压器的特点,设计了相应的试验装置,对油纸绝缘中的体击穿和沿面闪络进行了试验研究.本文实现了变压器油纸绝缘空间电荷的测量,根据空间电荷的实测结果对油纸绝缘系统中极性反转现象进行了探讨,对直流电...     

表面修饰纳米SiO_2/XLPE的电导电流和空间电荷特性

为研究纳米颗粒表面修饰对纳米二氧化硅/交联聚乙烯(SiO2/XLPE)电导电流和空间电荷特性的影响,分别将未经表面修饰和经钛酸酯偶联剂TC9修饰的纳米SiO2颗粒添加到XLPE基体中进行了实验。显微观测和成分分析表明,TC9的非极性有机官能团取代了纳米SiO2颗粒表面的羟基,降低了羟基间的相互成键作用,从而改善了纳米SiO2与XLPE基体之间的相容性,纳米SiO2颗粒在XLPE基体中的粒径范围从几十到100 nm;同时,TC9表面修饰提高了纳米SiO2/XLPE复合介质的介电常数和介质损耗,降低了电导电流,抑制了空间电荷的注入;而未经表面修饰的纳米SiO2/XLPE复合介质的电导电流和空间电荷特性相较于XLPE并未得到改善。分析认为,由于经TC9表面修饰的纳米SiO2分散性的改善,增大了纳米颗粒与XLPE基体之间的界面区域,因而在纳米复合介质内产生了更多的深陷阱;电极与介质界面附近的大量深陷阱捕获注入的电荷,形成固定的空间电荷层,降低了其与电极间的局部电场,从而提高了注入势垒,抑制了空间电荷的进一步注入。     

高压/超高压电力电缆关键技术分析及展望

随着电力工业规模的发展和发电、送电形式的多样化,城市用电、水电送出、海底送电、资源环境保护的需要,各类电缆的应用日益广泛,包括气体绝缘电缆(管道)的应用也逐步提上日程。在总结电缆发展历史、存在的问题和国内外发展现状的基础上,对电缆今后的重点发展方向进行了探讨。讨论了电缆研究和发展中存在的高性能材料、电树枝老化、空间电荷、绝缘结构及工艺和电缆运行检测等重要问题,认为今后相当长的时间内,直流电缆在输电中的应用将越来越受到重视,但也面临由于空间电荷和非线性温度特性引起的绝缘的可靠性和新型材料的开发问题。在强调电缆需求越来越大的同时,也指出了拓展电缆应用范围与社会、经济和环境提出的新要求密切相关。提出在未来电网中,由架空线路、电力电缆线路和气体绝缘管道3种送电方式构成的混合输电线路模式,以解决远距离、大容量架空输电线路由于高海拔、跨海和生态环境保护带来的线路瓶颈问题,并对该混合输电线路模式的技术问题和可能存在的社会经济意义进行了深入探讨。强调由于用电需求增大、城市规模扩大和应用环境复杂化,交直流电力电缆的应用规模将得到大幅度增长,电力工业将迎来电力电缆和气体绝缘管道发展的新时代,随之而来的可靠性和经济性问题则是制约其发展的关键因素。     

直流电压下变压器油纸绝缘局部放电的发展过程

研究变压器油纸绝缘局部放电(PD)的发展过程对于特高压换流变压器的运行维护十分重要。为此,对典型油纸复合绝缘缺陷模型在直流电压长期(100 h)作用下的局部放电信号进行了统计分析;根据其统计特征图谱,将直流局部放电发展过程划分为4个阶段。此外,还采用无感电阻测量直流局部放电单个脉冲波形;并对直流电压长期作用下的油浸绝缘纸板表面形貌变化进行了观测。试验结果表明,直流电压下的局部放电脉冲的上升沿在10～100 ns范围内,首脉冲持续时间约500 ns,其余振荡脉冲脉宽在600～900 ns范围内;估算得出单次直流放电脉冲能量在0.01～0.1 J范围内。此外,研究发现绝缘纸板的表面会在针电极电蚀作用下产生"凹坑",这为实现基于多信息融合的直流局部放电发展趋势预测奠定了基础。     

直流电场下低密度聚乙烯纳米介质空间电荷特性的数值分析(英文)

The dynamic characteristics of space charge in nanocomposite of low-density polyethylene (LDPE) mixed with inorganic nano- fillers. Different from previous qualitatively theoretical works, we investigated the influence of trap depth, trap volume charge density and injection barrier height on the space charge and the electric field distribution in the nanocomposite under a DC external electric field (100 MV/m) systematically and quantificationally, through numerical simulations based on a bipolar charge transport model. The simulation re- sults showed that, the increase of trap depth would severely distort the balanced electric field distribution with the highest and the lowest electric field of 119 MV/m and 47 MV/m, respectively. It is concluded that the introduction of nanofillers creates more deep traps, which would block space charges by capturing most of them in the vicinity of electrode and hence reduce the local electric field largely. Further theoretical analysis of the simulation indicates that both the high permittivity and the low local electric field of the nanocomposite contri- buted to the increase of injection barrier height, and almost no charge could overcome an injection barrier higher than 1.25 eV. At last, a mechanism of space charge suppression in the LDPE nanocomposite was presented.