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局部放电超高频信号时频特性与传播距离的关系 总被引:1,自引:0,他引:1
超高频(UHF)检测法具有频带宽、信息量大、抗干扰能力强等一系列优点,近年来在局部放电检测中得到了广泛应用。为此,建立了变压器油纸绝缘局部放电模型,研究了超高频电磁波信号与脉冲电流之间的对应关系,以及超高频电磁波信号与传播距离的关系。实验结果表明:1)随着传播距离的增加,超高频电磁波信号的能量和幅值均呈非线性衰减趋势;2)局部放电超高频电磁波信号幅值与脉冲电流幅值成正比关系,超高频电磁波信号能量与脉冲电流幅值的平方成正比关系,且比例系数随着超高频电磁波信号传播距离增加而减小;3)超高频电磁波信号中高频分量随着传播距离增加而衰减很快。以上结论有助于更加详细地了解局部放电超高频电磁波信号的辐射规律,是超高频检测法用来检测电力设备局部放电的依据。 相似文献
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直流电压下油纸绝缘中局部放电的超高频特性 总被引:3,自引:2,他引:1
为研究直流电压下油纸绝缘中局部放电的超高频特性,组建了一套直流电压下局部放电试验系统以及由局放超高频检测和超宽带检测组成的测量系统,其中脉冲电流超宽带检测的作用是确保超高频检测获取的信号来自于试品自身的局部放电。试验设计了6种油纸绝缘局放模型以模拟换流变压器的典型缺陷,并引入毫瓦分贝(DBM)频谱分析对超高频信号进行了统一化处理,以比较不同缺陷模型对应的超高频信号。直流下试验结果表明:局部放电电流脉冲具有极快的上升沿,能激励起大于300MHz的超高频电磁波,它可以通过超高频传感器加以耦合接收。各种缺陷模型局部放电的DBM频谱分布各异,超高频段能量幅值最大处也不一样。因此若想以高信噪比实现直流下局部放电超高频信号的在线监测,需要使用中心频率可调的窄带滤波器。这些特性为直流输电系统中使用油纸绝缘的电工设备进行局部放电超高频信号在线监测提供了试验依据。 相似文献
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油中局部放电检测脉冲电流法与超高频法比较 总被引:10,自引:6,他引:4
为了研究局部放电检测中超高频法参量与脉冲电流法参量之间的关系,比较分析了局部放电检测中超高频法和脉冲电流法在原理上的区别。利用脉冲电流法和超高频法对油纸绝缘的几种典型模型下的局部放电活动同时进行测量,比较分析同一模型下的局部放电中超高频法参量与脉冲电流法参量之间的关系并探讨了局部放电检测中脉冲电流法对超高频法的标定问题。研究表明,在反映放电活动强弱上,超高频法的参量和脉冲电流法的参量之间有着相同的变化趋势,但是二者之间不存在直接的线性关系。 相似文献
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The measured data transmission signaling performance for an AM broadcast (outbound) VHF radio (inbound) two-way distribution automation system is presented. The performance data are presented as a function of signal level, transmission path length and time of day. The outbound link, which uses inaudible low-speed phase modulation of the carrier of a standard AM broadcast station, demonstrated overall average signaling success rates of better than 99% in operational transceiver units. For the 154 MHz VHF return link, which used unconventional low-speed amplitude modulation resolved by a real-time FFT detector-receiver, the measured overall signaling success rate averaged about 60% 相似文献
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van Breen H.J. Gulski E. Smit J.J. Verhaart H.F.A. de Leeuw W. Krieg-Wezelenburg M. 《Dielectrics and Electrical Insulation, IEEE Transactions on》2002,9(1):140-149
Based on field experiences on a number of different turbo-generators in the Netherlands, several fundamental and applied aspects of on-line very high frequency (VHF) partial discharge (PD) diagnostics are discussed. In particular the systematic results presented in this paper contribute to: 1. the characteristics of different on-line detection using suitable VHF sensors, 2. the methods to suppress disturbances and to distinguish between different types of discharges and 3. the interpretation of measured results to obtain knowledge about the insulation condition 相似文献
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《Dielectrics and Electrical Insulation, IEEE Transactions on》2004,11(6):1057-1064
A VHF method (30-300 MHz) is applied to identify faults and defects in ceramic insulators. Insulators which exhibit internal cracks and fractures are used as test samples. Different artificial conditions are introduced to the test samples according to the IEC 507 standard under wet and dry conditions. Using a cascading signal processing technique and analysis methods such as FFT and fractal analysis, VHF signals acquired by digital scope are processed and analyzed. This study indicates that the fractal dimension can be used as an effective tool to isolate the common faulty conditions found on the ceramic insulators. The results from this study strongly support the prospect of using a VHF method to monitor the physical condition of ceramic insulators. 相似文献
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Ju Tang Qian Zhou Ming Tang Yanbin Xie 《Dielectrics and Electrical Insulation, IEEE Transactions on》2007,14(1):30-38
Very high frequency (VHF) measurement is a valid technique for partial discharge (PD) detection, and PD mathematical models are very important to study PD denoising and waveshape pattern recognition etc. However, these mathematical models based on the traditional PD measurement have been established according to RC or LCR resistance detection so that they are not suitable for VHF measurements. PD signals are detected based on four typical physical models of defects in gas insulated substation (GIS) using VHF method. The VHF PD mathematical models are established, and the principles and methods of establishment are summarized. Furthermore, the parameters of the mathematical models are given and the validity of PD mathematical model is proved by fitting error, power spectrum and time-frequency analysis. Results show that the VHF PD mathematical models can facilitate theoretical simulation of different insulated defects by using the values of given parameters. In the end, applications of the VHF PD mathematical models and complex wavelet transform for extracting the relevant signals from a white noise background are illustrated 相似文献
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利用时间分辨率为0.1ms的快天线电场变化和126MHz(带宽6MHz)甚高频(VHF)辐射资料,对甘肃平凉地区雷暴过程中闪电辐射特征进行了分析研究;并引入脉冲丰度这一概念,对地闪各特征阶段VHF辐射脉冲进行定量分析。统计分析发现:在地闪首次回击前,各特征阶段脉冲丰度有明显不同,回击过程脉冲丰度最高,并且其VHF辐射脉冲幅值远大于其余阶段;而在回击之后,有时仍存在很强的VHF辐射,其辐射脉冲幅值甚至超过了回击过程和梯级先导过程;云闪的初始阶段VHF辐射会有间歇性变化,其脉冲序列持续时间一般很短,活跃阶段VHF辐射脉冲较丰富,云闪末尾阶段VHF辐射脉冲稀少。最后对这些现象进行了理论探讨,认为地闪各特征阶段脉冲丰度的明显不同,是地闪各阶段放电强度以及放电机制的不同造成的。 相似文献
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特高压输电线路工程的建设对于实现远距离电力系统互联十分关键,随着特高压输电线路工程的建设,其对线路临近的甚高频信号(30~300 MHz)的无源干扰问题亟待解决。针对矩量法计算量的局限性以及现有特高压输电线路甚高频无源干扰问题尚没有确定的求解方法的问题,建立了特高压输电线路无源干扰的面模型,提出了采用迭代物理光学法(iterative physical optics,IPO)对甚高频特高压无源干扰问题进行求解的思路。以甚高频频段(30~300 MHz)为例,根据IPO理论,对特高压输电线路模型中存在的不连续情况进行了修正,对该频段下的无源干扰问题进行了求解。研究表明,采用IPO方法可以实现对甚高频特高压输电线路无源干扰问题的求解,也为该问题的确定求解方法提供了可行的思路。 相似文献
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基于VHF的交联电缆附件局放检测的研究 总被引:3,自引:1,他引:3
为在线检测XLPE电缆附件局放,基于电磁耦合法设计了VHF宽频带钳型电流传感器,该传感器检测频3~60 MHz,灵活方便、操作安全,易于安装,还建立了XLPE电缆附件和几种典型的电缆局放模型(气泡放电,毛刺放电等)。试验表明,不同局放类型统计特征谱图不同;VHF检测技术与传统检测方法的检测结果一致性较好。 相似文献
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针对甚高频脉冲谐振频率随回路阻抗变化而迁移导致脉冲电压幅值变化及甚高频脉冲双极性特点导致传统检测方法无法适用的问题,提出了基于极间分压检测的甚高频EDM放电状态检测方式。利用分压、整流、滤波多模块共同作用实现对极间高频高压双极性脉冲到低压单极性直流信号的转换,同时通过检测直流信号则可以直接表征出当前开路电压大小及极间放电状态的变化。在仿真及实验验证检测方法可行性的基础上,设计出基于该检测方案的放电状态检测系统及相应检测算法,成功验证了甚高频微纳电加工所需的脉冲频率自动寻优技术及甚高频放电状态检测的有效性,有利于提升甚高频电火花加工过程中放电状态检测精度。 相似文献