局部放电在线监测的数据分析及现场干扰抑制

分析总结了局部放电在线监测数据及现场干扰抑制的经验,基于变压器油中局部放电特征的试验研究提出了小波变换局部放电干扰抑制法。该法充分利用局部放电信号特征,采用多尺度分析及多工频周期叠加方法抑制干扰。数据处理结果表明该法可有效抑制现场局部放电测量中的白噪、周期性窄带及随机性脉冲干扰。     

交流特高压变压器局部放电试验干扰信号排查案例分析

结合交流特高压变压器局部放电现场试验排除外部干扰的案例,分析总结了不同方法的适用性,为提升现场局部放电试验质量提供了帮助.     

大型变压器局部放电的现场测量

大型变压器在现场进行局部放电测量,要解决两个主要问题,电源和干扰。本文以十几台500千伏和220千伏变压器的局部放电现场实测为例,着重介绍了使用调压器并电容补偿的几种常用加电方法、“多端测量法”以及如何识别并排除背景和电源干扰等,对现场使用有一定参考价值。     

大型电力变压器局部放电试验干扰排查

介绍不同干扰信号对局部放电的影响,提出局部放电试验系统外部干扰和内部干扰的排查方法,结合一起500kV变压器现场局部放电试验中的干扰排查实例,分析试验干扰排查的过程及干扰源判断方法,为现场局部放电试验干扰信号处理提供借鉴。     

GIS超声波局放检测现场典型干扰分析

超声波局部放电检测法是检测气体绝缘组合电器(GIS)绝缘状况的重要手段。对GIS进行超声波法局部放电检测时,现场会遇到机械振动、外部电晕干扰和磁致噪声这三种典型的干扰,这三种干扰与放电特征图谱相似,极易对检测人员造成误判。结合现场实测经验,分析了三种典型干扰的信号特征,提出了现场干扰的判别及排除方法。文中提出的干扰辨别及排除方法在现场超声波局放带电检测中取得了良好的效果。     

变压器现场局部放电试验有关问题的分析

总结了近年来多台次变压器现场局部放电试验的情况,分析了试验时容性无功容量的估算方法,通过与实际容量的对比,验证了估算方法的可行性。同时通过实例,分析了现场试验中典型干扰的抑制排除方法,展望了变压器局部放电技术的发展趋势。     

变压器套管末屏对现场局部放电测量影响分析

介绍了使用变频电源进行现场局部放电测量的方法,分析了套管末屏对现场局部放电测量的影响,并提出了处理方法.     

油中局部放电UHF频带选取及干扰的抑制

为消除变压器局部放电对现场测量的干扰,在对绝缘油中局部放电特高频信号频谱特征研究基础上,给出了特高频法测量绝缘油中局部放电的频率范围;为满足实际测量要求。采用包络检波方法对放大后的特高频信号进行降频处理;同时,提出了高频与特高频联合测量方法,用来消除现场局放测量中的干扰。对现场测量数据的处理结果表明,所提出的方法可很好抑制干扰信号。     

局部放电UHF脉冲干扰的排除与信号的聚类分析

为了排除变压器局部放电信号中的各种信号干扰中的脉冲干扰信号,提出了利用内外信号对比法及相间信号对比法排除外部脉冲型干扰信号,并应用于500kV三相分体式变压器的局部放电现场监测。通过提取工频周期上特高频检波脉冲信号的特征参数,选取脉冲初始相位、平均脉冲幅值、脉冲次数3个特征参数,采取灰聚类与模糊聚类相结合的方法对排除干扰后的数据进行了聚类分析,实现了对部分干扰信号的排除以及特高频信号的分类。对分类后的疑似放电信号的现场特高频检波信号进行统计分析,通过分析PRPD谱图对变压器的局部放电活动做出了诊断说明。通过分析表明,提出的方法能够有效排除干扰信号,便于提取局部放电故障信息。     

某水电站110 kV主变压器局部放电定位分析与处理

变压器由于运行环境的限制,在进行局部放电带电检测时,现场一般干扰因素较多,需要对众多干扰因素进行仔细排除,对局部放电进行定位时,亦会受到内部结构复杂性、信号传输不确定性的影响。文章介绍了某水电厂110 kV主变压器局部放电带电检测过程,包括现场检测、分析与定位,为设备缺陷维护保养提供了较为科学的处理策略。     

±800kV换流变压器现场局部放电试验的干扰监测

研究干扰识别和定位技术是解决换流变压器现场局部放电测量难题的关键。针对南方电网开展的国内外首次现场修复±800 k V换流变压器的试验要求,采用特高频(UHF)法对局部放电测量干扰进行了旁路监测,通过分析UHF检波信号的波形特征和相位分布统计特征验证了现场检修试验厂房对换流站电磁辐射的屏蔽效果,通过UHF天线阵列精确定位并妥善处理了厂房内的多种局部放电干扰源,支撑被试的±800 k V换流变压器顺利通过了各项试验,视在放电量满足了出厂试验的限值要求。为今后研究在无厂房条件甚至运行条件下实现换流变压器局部放电水平的精确评价提供了技术基础。     

110kV交联电缆交接试验中带电局放检测及干扰抑制分析

笔者介绍了某新建变电站工程110 kV交联聚乙烯电缆交接耐压试验中实施局放检测的过程,通过对谐振系统加装屏蔽及抑制措施,在局放测试系统中设置滤波和检测频带,减少背景噪声干扰,提高了检测系统信噪比。检测结果证实了搭建的局放检测平台和干扰抑制方法对现场检测电缆局放的有效性,为今后开展现场电缆局放带电检测提供参考。     

Rejection of narrow-band noise and repetitive pulses in on-site PDmeasurements [corrected version]

This paper deals with the possibilities of noise suppression in partial discharge (PD) measurements under on-site conditions. After the presentation of previous work, a new concept of designing a digital FIR filter with a fixed order to suppress narrow-band disturbances is presented. The method is compared to a design using adaptive filters. A filter device, which was developed as an extension for a conventional PD detector, is presented. In the second part of the paper, a method for suppressing pulse shaped noise synchronous to the test voltage is discussed. The disturbing pulses are detected automatically in a PD signal by comparing several recorded cycles of the test voltage. There are two possibilities of suppressing the pulses. The first one is an off-line method that allows attenuation degrees up to 30 dB, the second one works on line, and can process continuous PD signals. For the latter case a suppression of 14 dB for worst case pulses is possible with the developed hardware. In order to demonstrate the abilities of the filters, several measurements are shown     

局部放电检测中傅立叶级数法与几种抗干扰方法的比较分析

提出了一种新的抗窄带干扰方法,傅立叶级数法.首先利用原始局放数据估算窄带干扰的频率和傅立叶级数的系数,然后利用傅立叶系数估算窄带干扰波形,再将原始数据与估算结果相减,则窄带干扰被抵消而局放脉冲得以保留.文章利用仿真数据和现场试验数据分析了该方法的抗干扰效果,并与常用的数字滤波器、时频转换法、自适应滤波和小波滤波等方法进行了比较.发现该方法能够较好地消除窄带干扰,同时尽量保留了局放脉冲的幅值和极性特征.特别是在脉冲的主要频谱与窄带干扰的频谱非常接近时,傅立叶级数法的抗窄带干扰效果更明显.     

Wavelet-based denoising of partial discharge signals buried in excessive noise and interference

Achieving acceptable levels of sensitivity during online and/or onsite partial discharge (PD) measurements still continues to remain a very challenging task, primarily due to strong coupling of external (random, discrete spectral and stochastic pulsive) interferences. Many analog and digital approaches have been proposed for suppressing these interferences, and amongst these, rejection of the pulsive type of interferences is known to be very difficult, if not impossible. The time and frequency characteristics of the pulsive interference being very similar to that of the PD pulses is the main reason posing difficulty in their separation. In this paper, a novel, semi-automatic, and empirical wavelet-based method (using multi-resolution signal analysis) is proposed to recover PD pulses, buried in excessive noise/interference comprising of random, discrete spectral, pulsive, and any combination of these interferences occurring simultaneously and overlapping-in-time with the PD pulses. A critical assessment of the proposed method is carried out, by processing both simulated and practically acquired PD signals. The results obtained are also compared with those from the best digital filter (infinite impulse response, IIR and finite impulse response, FIR) method proposed in literature. From the results it emerges that, the wavelet approach is superior and further, has the unique capability of successfully rejecting all the three kinds of interferences, even when PD signals and one or all interferences occur simultaneously and overlap-in-time.     

Rejection of narrow-band noise and repetitive pulses in on-site PDmeasurements

This paper deals with the possibilities of noise suppression in partial discharge (PD) measurements under on-site conditions. After the presentation of previous work, a new concept of designing a digital FIR filter with a fixed order to suppress narrow-band disturbances is presented. The method is compared to a design using adaptive filters. A filter device, which was developed as an extension for a conventional PD detector, is presented. In the second part of the paper, a method for suppressing pulse shaped noise synchronous to the test voltage is discussed. The disturbing pulses are detected automatically in a PD signal by comparing several recorded cycles of the test voltage. There are two possibilities to suppress the pulses. The first one is an off-line method that allows attenuation degrees up to 30 dB, the second one works on line, and can process continuous PD signals. For the latter case a suppression of 14 dB for worst case pulses is possible with the developed hardware. In order to demonstrate the abilities of the filters, several measurements are shown     

基于向量分析法的三相交联电缆局部放电检测与分析识别技术

三相交联电缆的局部放电诊断易受到外界环境、相间串扰等因素的影响。为了解决信号的串扰问题,介绍了基于向量分析法的三相交联电缆局部放电检测与识别技术。该方法基于不同的局放脉冲衰减程度不同的原理,利用三相信号脉冲组的幅值关系构建三相幅值相位关系图,用来区分外部噪声和内部局放信号,同时分离不同的局放源。通过理论研究与现场实例的分析可以得出结论,该方法在高压交联电缆的局放诊断方面具有较好的可行性和优越性,可有效应用于三相交联电缆局放现场检测和绝缘诊断。     

Advanced partial discharge diagnostic of MV power cable systemusing oscillating wave test system

To obtain a sensitive picture of discharging faults in power cables the PD should be ignited, detected, and located at power frequencies that are comparable to operating conditions at 50 or 60 Hz. In this way, realistic magnitudes in [pC] and reproducible patterns of discharges in a power cable can be obtained. PD measurements during service as well as on-site continuous energizing at 50 (60) Hz of MV cables are not always economically realistic for on-site inspections. Different energizing methods have been introduced and employed during recent years. Therefore, based on the assumption that sensitive detection of critical PD sites occurs by a method mostly similar to 50 Hz energizing conditions, a method as introduced for on-site PD diagnosis of MV cables is discussed: oscillating wave test system (OWTS)