含缺陷PTFE绝缘管型母线模型的局部放电信号特征分析

聚四氟乙烯(PTFE)绝缘管型母线具有载流量大、绝缘及力学性能好等优点,已经在我国变电站中获得广泛应用。在管型母线的生产、安装和运行过程中,可能在绝缘层内引入缺陷,诱发局部放电。长期受到局部放电的侵蚀作用,PTFE绝缘将出现加速老化导致母线绝缘击穿而引发事故。针对管型母线中典型绝缘缺陷引发的局部放电信号特征进行分析,对于辨识母线中局部放电的种类,评估其绝缘状态具有重要意义。采用PTFE薄膜建立了三种含典型缺陷的管型母线模型,通过高频电流互感器测量了交流高压作用下缺陷引发的局部放电信号,分析了局部放电的相位分布、放电频次-幅值关系、单次脉冲波形及频域谱等信号特征,讨论了外施电压的影响。结果表明不同缺陷模型引发的局部放电相位分布、放电频次-幅值等特征均有着明显的区别;放电幅值及每周波放电次数均随外施电压升高而增大。     

局放检测技术在10kV管型母线故障检测中的应用

针对某110 kV变电站10 kV变低管型母线在红外测温过程中2#主变B相变低管型母线出现测温异常的情况,采用常规停电方法测量具有一定的局限性,通过采用脉冲电流局放检测法及极性定位法查明缺陷原因,并解体进一步验证试验及分析结果。结果表明:10 kV管型母线的绝缘电阻、介质损耗及电容量、回路电阻等常规测试手段在绝缘受潮初期检测过程中具有一定的局限性,脉冲电流局放检测法能很好地弥补这些不足,可以在10 kV管型母线的检测中推广使用。     

几种合成绝缘子带电检测方法的比较

分析了观察法、电场法、紫外成像法和红外成像法这 4种合成绝缘子带电检测方法的实验室和现场运行情况 ,总结出它们不同的主要适用范围 :观察法、电场法分别适于外绝缘、导通性内绝缘缺陷 ;紫外成像法、红外成像法分别适于能产生局部放电、局部发热的缺陷。比较而言电场法成本低廉 ,直接检测 ,准确可靠 ,操作简单 ,更适于国内推广使用     

绝缘管型母线运行特性及状态评估方法

绝缘管型母线由于具有优异的电气性能在电力系统中使用逐年增多,但作为一种新型电气设备,国内外尚无统一的规范,导致绝缘母线市场混乱,投运后陆续出现了击穿、烧蚀、破损、进水等异常运行现象,而国内外对管母的结构工艺、电气性能、状态评估方法等均研究甚少。为此全面分析了绕包式、挤包式、浸胶式3类绝缘母线的结构与关键工艺,结合已投运母线的运行特性,对其主绝缘、外护套、中间连接件、终端、接地方式等薄弱点进行分析研究。研究结果表明:绝缘母线中间连接件与终端的电场集中与密封不严,是母线故障的主要原因;交流耐压、高频局部放电检测、红外测温、接地引下线电流检测是绝缘管型母线运行状态的有效评估方法。对交流耐压试验,应尽量在开展交流耐压的同时进行局部放电检测,且须在一较高电压下持续足够时间,使缺陷能有充分的时间发展到可检测范围,以发现运行隐患点。     

绝缘管型母线绝缘缺陷红外检测技术的研究与应用

绝缘管型母线绝缘缺陷的试验与排查手段缺乏。通过两起红外测温发现管母受潮和现场解体处理情况,结合管母结构,分析管母受潮发热的原理,论述红外测温是发现管母绝缘受潮缺陷的有效手段。通过专项排查,又发现了多起类似的缺陷,验证了该方法的有效性。     

110kV GIS局部放电缺陷的分析与处理

本文介绍了一起由于隔离开关合闸不到位引起的GIS内部发热并伴随局部放电的缺陷,运用超声波及特高频局部放电检测、红外测温、SF_6组分检测等技术进行了综合诊断,分析了造成缺陷的原因,对类似缺陷的处理具有一定的借鉴意义。     

管型母线绝缘材料的老化研究进展

绝缘管型母线具有占地面积少、功率损耗低和通流容量大等特点,在电力系统中具有广阔的应用前景。管型母线的绝缘老化是影响其长期稳定运行的重要因素。对近年来国内管型母线的相关研究进行了评述,对目前母线的结构类型、绝缘种类及成型工艺进行了总结,分析了可能产生的绝缘缺陷和潜在隐患,介绍了关于管型母线绝缘的热老化、局部放电老化的研究情况,为安全使用管型母线、保障电力系统安全提供了参考和借鉴。     

110kV主变套管污秽缺陷的诊断分析与处理

在变电站高压设备巡视中通过红外检测发现运行中的110 kV主变压器套管局部发热异常。综合应用红外、紫外成像和超声波局放检测技术诊断瓷套管存在裂纹或污秽缺陷。停电检查套管发现其表面积污严重,部分伞裙有明显的放电痕迹。分析认为引起发热和局部放电异常的原因是瓷套管表面污秽受潮。对瓷套管表面进行喷涂PRTV涂料处理后,套管带电检测数据正常,消除了套管缺陷,并提出了防污闪的建议。     

应用多种带电检测技术联合诊断设备缺陷效果分析

本文介绍了红外测温、SF6气体检测、局部放电类检测等带电检测技术的原理及应用现状。采用红外测温方法发现某变电站500 kV套管过热异常情况后,又采用SF6气体检测及特高频局部放电检测方法确定了造成套管缺陷的原因为套管内部导体接触电阻过大引起套管发热。通过将套管解体分析验证了该结论的正确性,证明了采用多种带电检测技术联合诊断设备缺陷方法准确、可靠。最后提出了完善带电检测工作的措施建议,为深入推进输变电设备带电检测以及状态检修工作提供了参考。     

非有效接地系统管型绝缘母线接地故障分析及处理建议

针对某电厂管型绝缘母线接地故障导致发电机停运的问题,分析了其在非有效接地系统中发生接地故障的原因,通过采用局部放电检测、高压试验与红外检测相结合,抑制系统发生铁磁谐振过电压的方法,解决了管型绝缘母线接地的问题,最后提出建议及预防措施:重置线路保护定值,确保灵敏性,采取在电压互感器开口三角绕组两端接阻尼电阻、按分频消谐装置等措施消耗谐振能量,破坏谐振条件。     

谐波的分类、检测与判别

近年来,随着用电设备的急剧增加,同时也给电网注入了大量的谐波,造成电网污染,使电力系统的发、供、用电设备出现许多异常现象与事故,必须引起我们的高度重视。     

System Grounding, Protection, and Detection for Cement Plants

Safety of personnel and equipment requires proper attention to power system and equipment grounding. The National Electrical Code, MSHA, IEEE, ANSI, and federal, state, and local codes contain regulations or recommendations on system and equipment grounding. Proper grounding practice can be achieved with several different methods and combinations of equipment. The use of ``portable' equipment in quarries requires specific grounding method and ground check monitoring. Current practice and recommendations on ground fault detection and protection in modern cement plants and associated quarries are discussed.     

Detection,classification, and location of faults in power transmission lines

This paper presents a pattern recognition approach for current differential relaying of power transmission lines. The current differential method uses spectral energy information provided through a new Fast Discrete S-Transform (FDST). Unlike the conventional S-Transform (ST) technique the new one uses different types of frequency scaling, band pass filtering, and interpolation techniques to reduce the computational cost and remove redundant information. Further due to its low computational complexity, the new algorithm is suitable for real-time implementation. The proposed scheme is evaluated for current differential protection of a transmission line fed from both ends for a variety of faults, fault resistance, inception angles, and significant noise in the signal using computer simulation studies. Also the fundamental amplitude and phase angle of the two end currents and one end voltage are computed with the help of the new formulation to provide fault location with significant accuracy. The results obtained from the exhaustive computation show the feasibility of the new approach.     

On Color-, Infrared-, and Multimodal-Stereo Approaches to Pedestrian Detection

This paper presents an analysis of color-, infrared-, and multimodal-stereo approaches to pedestrian detection. We design a four-camera experimental testbed consisting of two color and two infrared cameras for capturing and analyzing various configuration permutations for pedestrian detection. We incorporate this four-camera system in a test vehicle and conduct comparative experiments of stereo-based approaches to obstacle detection using unimodal color and infrared imageries. A detailed analysis of the color and infrared features used to classify detected obstacles into pedestrian regions is used to motivate the development of a multimodal solution to pedestrian detection. We propose a multimodal trifocal framework consisting of a stereo pair of color cameras coupled with an infrared camera. We use this framework to combine multimodal-image features for pedestrian detection and to demonstrate that the detection performance is significantly higher when color, disparity, and infrared features are used together. This result motivates experiments and discussion toward achieving multimodal-feature combination using a single color and a single infrared camera arranged in a cross-spectral stereo pair. We demonstrate an approach to registering multiple objects across modalities and provide an experimental analysis that highlights issues and challenges of pursuing the cross-spectral approach to multimodal and multiperspective pedestrian analysis.     

Sensitive,On-Line Turn-to-Turn Fault Detection in AC Motors

Turn-to-turn fault detection is based on the principle that symmetrical (unfaulted) motors powered by symmetrical multiphase voltage sources will have no negative sequence currents flowing in the leads. A turn-to-turn fault will break that symmetry and give rise to a negative sequence current which may then be used as a measure of fault severity or to initiate protective action, such as a circuit breaker trip. A new way of looking at the effects of turn faults has been developed that improves sensitivity andspeedwhile reducing the probability of misdetection, taking into account voltage balance, load or voltage variation, and instrument errors. The method has been implemented on a PC and tested, in real time, with controllable faults in a small motor. Reliable detection of one shorted turn out of 648 turns per phase (in a Y-connected motor) was demonstrated with the fault indicator becoming fully developed in two cycles of line frequency after initiation of the fault.     

基于i_p、i_q算法的谐波电流检测的仿真

介绍了目前应用广泛的基于瞬时无功功率理论的ip、iq算法原理、算法单个矩阵模块Simulink仿真模型的搭建过程和谐波电流检测仿真系统。选择不同的二阶低通滤波器(LPF)的截止频率,得出不同的滤波效果。结合有源电力滤波器(APF)的实时性和准确性,选择最佳截止频率,给出了滤波后的单相电流波形谐波畸变分析,对实现实际电路的滤波有较好的参考作用。     

超声波局部放电检测装置的检测及校验

超声波传感器及超声波局部放电检测装置的准确性、可靠性对于检测和保护电力设备的安全性至关重要,所以对超声波局部放电检测装置有效性的检定十分必要。文章主要分析了超声波局部放电检测装置的检测与校验系统的设计思路、构建了基于PCI总线工控机的系统结构和研究了超声波测试平台、局放信号超声波模拟模块和超声波信号采集模块的实现方法,这对于超声波局部放电检测装置性能的检测与校验方法以及相关系统的研制具有指导意义。     

电阻型电流检测在伺服系统故障检测中的应用

提出一种应用于伺服系统故障检测的电阻型电流检测方法。该方法采用电阻和光电耦合器进行电流检测,检测精度高,而且系统的性价比也得以提升,为伺服系统的故障检测和实际应用提供了新思路。     

高频电流局放和X光检测在高压电缆带电检测中的应用

随着交联聚乙烯(Cross-linked Polyethylene,XLPE)高压电缆在城市地下电网中广泛投运,其安全运行对于电网稳定越来越重要,找到切实可行的方法来监测现场运行电缆的绝缘势在必行。高频电流法是一种非侵入式的检测方法,安全可靠,针对某110 k V高压电缆接头绝缘击穿事故,对同结构电缆头进行局部放电,发现疑似局放信号并确定了其局放源,验证了此方法的实用性;X光检测是一种可实时成像的新型检测技术,通过一起电缆主绝缘击穿事故的X光检测,表明了利用X射线数字成像技术,可实现电缆内部结构的可视化诊断,快速准确的评估电缆缺陷程度。电缆高温运行实例将两方法综合应用,进一步验证了其有效性,为XLPE高压电缆局放带电检测提供理论支持。     

交联聚乙烯电力电缆水树产生机理、检测及预防

分析交联聚乙烯电力电缆绝缘中水树产生的机理及检测方法,并对如何防止绝缘中水树产生提出了解决措施。