Real-time PD identification in diagnosis of GIS using symmetric and asymmetric UHF sensors

A new practical method for real-time insulation diagnosis of gas-insulated switchgear (GIS) has been developed and introduced. A notable technique, which takes the output ratio of a symmetric ultra-high-frequency (UHF) sensor (e.g., a loop electrode) to an asymmetric one (e.g., a conical coupler), makes it possible to immediately identify defects and also to eliminate noises because the output ratio of those UHF sensors strongly depends on the radial position of the GIS. It would be remarkably effective for dc power transmission, intermittent partial discharge (PD), and sequential risk assessment based on each identified PD pulse, which would support condition-based maintenance.     

GIS内部局部放电检测的研究

根据测量系统等效电路的传递函数的幅频特性图,优化设计了CT线圈测量系统和外被电极测量系统,CT线圈测量系统有一个较好的频率选择特性,有一个可以减少外界干扰的谐振频率,当第一个谐振点频率约为100kHz时,CT线圈测量系统的测量灵敏度为2～10pC,外被电极测量系统的灵敏度为15～30pC,应用这两种测量系统,对充有SF_6或SF_6/N_2或SF_6/空气混合气体且带有固定微粒或自由微粒的同轴电极系统,获得了一些检测局部放电的结果。     

GIS中局部放电电磁波的模式特性

超高频法(UHF)通过检测GIS中局部放电(简称局放)时产生的超高频电磁波信号实现局放检测,具有灵敏度高、抗干扰能力强等优点,在GIS现场在线监测中得到了广泛的应用和关注。为进一步研究GIS中局放产生的电磁波特性,从局放源的激励特性出发,采用时域有限差分法(FDTD)进行仿真计算分析,着重研究了GIS中局放激励的电磁波模式分布特性以及各模式分量与局放源之间的关系。研究结果表明,GIS中局放激励的电磁波各高次模式中TE11(0°)、TE21(0°)、TE31(0°)模式分量为相应模波的主导分量,电磁波信号在φ为0°和180°处最强,且电磁波各模式分量的大小与局放脉冲波形、局放源位置、局放通道长度等因素之间具有一定的关系特性。     

GIS设备局放类型图谱以及现场局放测试诊断图谱的应用

笔者介绍了现场GIS的检测方法,包括特高频与超声波检测法;而且通过现场大量的实测案例,总结出由特高频与超声波检测方法所得出的局放类型图谱;同时将局放类型图谱与GIS的具体部位结合得出GIS现场局放测试的诊断图谱,并通过一起应用实例,证明了该诊断判据的有效性。     

变压器超高频局部放电自动识别系统

本文研制了一套变压器超高频局部放电自动识别系统，详细介绍了系统的硬件和软件实现。硬件主要包括超高频天线和频谱分析仪，软件由信号采集，统计谱图生成，统计算子（指纹）计算，用基于遗传算法的神经网络进行模式识别四部分组成，在实验室中对变压器典型局放模型进行实验，结果表明，该系统可以很好地用于提取高频（中心频率在500－1000MHz之间可调）窄带（带宽5MHz)时域放电信号，并且具有强大的数据处理，显示、分析、识别等功能，从而为变压器超高频局部放电检测以及绝缘状态评估提供了丰富的信息。     

Application of Maxwell solvers to PD Propagation. III. PD propagation in GIS

A transient electromagnetic field analysis by the method of moments (MoM) has been used to simulate the propagation of high-frequency PD pulses in electric power equipment. The analysis of transient electromagnetic fields described here enables the propagation of high-frequency signals in electric power equipment to be displayed. The motivation for this work is the expectation that such computational methods will provide an improved basis for the application of PD-based diagnostics to power apparatus.     

Accelerated microwave-assisted hydrothermal/solvothermal processing: Fundamentals,morphologies, and applications

This article is designed to serve as a roadmap for understanding the fundamentals, the key advantages and the potential applications of microwave-assisted hydrothermal/solvothermal (MAH/S) processing. MAH/S synthesis is a versatile chemical method for preparing a diversity of materials such as metals, semiconductors, electroceramics, graphene and their composites as bulk powders, thin films, or single crystals. The key to improve performance of these materials is achieving controlled morphologies (0 to 3D dimensionality) that favor desirable physical-chemical phenomena at the surface, and in the bulk of these advanced materials. The main features related to the improvement of the thermal and non-thermal effects associated with the use of microwave power concurrently with hydrothermal or solvothermal methods are discussed. Furthermore, the main crystal growth mechanisms (Ostwald ripening and oriented attachment) of these solids in solution under MAH/S treatment are described. Products synthesized by the MAH/S, particularly of interest in the development of gas sensors, batteries, fuel cells, solar cells and photocatalysts are emphasized. We conclude by envisaging new future directions for the use of this rapid and versatile processing approach.     

一种用于GIS超高频检测的滤波器

为提高使用外置天线的GIS超高频检测系统的信噪比,设计了一种工作频带300~1000MHz的微带线带通滤波器。根据微带线滤波器设计原理,确定滤波器类型、结构和级数,利用先进的EDA仿真工具进行结构仿真和优化并提出了一种减小滤波器尺寸的方法。特性曲线和实测性能表明,该滤波放大器能抑制低频干扰信号,放大局放信号,提高信噪比,从而满足了UHF微弱信号滤波预处理要求。     

GIS中局部放电在线监测现状及发展

对GIS中局放的在线监测现状进行了综述,并指出了目前在GIS局放监测中存在的问题及发展趋势。     

GIS中局部放电特高频信号与放电严重程度的关联分析

局部放电激发的特高频信号大小与放电严重程度紧密相关,笔者利用220 kV GIS设备,采用特高频检测法和IEC 60270—2000检测法同时对多种典型局部放电源进行试验。通过分析特高频信号的时域峰峰幅值与局部放电量之间的关联,发现不同类型局部放电源所激发的特高频信号峰峰值与视在放电量的对应关系存在显著差异。针对不同局部放电源特有的物理结构,通过对放电机理的对比分析,给出了不同缺陷激发的特高频信号峰峰值与视在放电量关系不一致原因的定性解释。     

Frequency domain discussions on PD signal propagation characteristics in GIS

The frequency dependency of PD signal propagation in GIS was investigated at an underground substation. Injecting dummy pulses into a GIS through its internal electrode, frequency spectra were measured by a spectrum analyzer at various points of the GIS. It is shown that this measurement is very reproducible and the signal propagation phenomena are independent of its direction. It is also clarified that the PD signal reduction phenomena are closely related with mode transfer from TEM to TE or TM. The major higher mode seems to be TE₁₁. Pulse waveforms were also measured with 65‐MHz bandpass filter. Their magnitudes are compared with the gain of the 65‐MHz component of the frequency spectra and good agreement is obtained. This implies the possibility of PD location by observing a frequency pattern with several bandpass filters. © 2000 Scripta Technica, Electr Eng Jpn 133(3): 9–17, 2000     

运行中GIS局部放电超高频-超声波的联合检测

介绍了运行中GIS局部放电检测所常用的两种方法：超高频发和超声波法。对两种方法的检测原理、使用范围、抗干扰能力等各自的优缺点进行了阐述。联合使用两种方法同时对运行中的GIS进行了局部放电的现场检测,对现场使用中需要注意的问题及联合检测的优越性进行了论述。对使用超高频-超声波联合诊断的结果判别方法进行了说明。     

GIS中局部放电与超高频电磁波关系的仿真研究

GIS内部由于存在各种绝缘缺陷而发生局部放电时,会激发起数百MHz至数GHz的超高频(UHF)电磁波在GIS腔体内传播。笔者根据电磁波在同轴波导中的传播理论,运用有限差分时域(FDTD)算法,对局部放电脉冲波形与其激发UHF电磁波之间的关系进行了仿真分析。首先研究了局部放电量与电磁波电场强度的关系,指出在一定的局放脉冲电流变化率下局放量的变化对电磁波电场强度的影响较小;然后研究了局放脉冲电流变化率与电磁波电场强度的关系,指出在局放量一定时二者近似呈线性关系;最后研究了局放脉冲电流变化率对电磁波中高次模成分的影响,运用变异系数对高次模成分在电磁波中所占比例大小进行分析,指出高次模成分所占比例随局放脉冲电流变化率的增大而增大。     

Comment and discussion on digital processing of PD pulses

Some of the more salient aspects of the digital processing technology of PD signals are examined. Most of the efforts in this field are concentrated on the application of digital analyzers for pulse height analysis, pattern recognition and identification of the physical phenomena. It is demonstrated that errors in the signal processing unit can lead to dominant mistakes in the interpretation of the test results     

GIS中金属微粒诱发沿面局部放电发展过程的研究

局部放电的检测和识别对气体绝缘全封闭组合电器(GIS)运行状况的监测起着至关重要的作用。金属微粒缺陷是一种极易引发GIS局部放电的典型缺陷。文中主要研究金属微粒诱发的GIS内局部放电沿面爬电的发展过程。为此,根据GIS实际运行条件,搭建GIS模拟实验平台,采用阶梯升压法划分试验阶段,利用脉冲电流法检测各阶段下的局部放电模式,与此同时架设增强型电荷耦合检测器相机(ICCD)实时记录金属微粒局部放电的沿面发展过程,并采用K-Means聚类算法结合特征参量对其发展过程进行划分。结果表明GIS盆式绝缘子上金属微粒的沿面局部放电演变过程分为3个阶段:电晕放电主导阶段、电晕与流注放电并存阶段和流注放电主导阶段。     

GIS局部放电在线检测中滤波器的应用

在GIS设备绝缘局部放电检测中,各种因素将会产生各种不同的干扰.局部放电信号的测量为GIS内部绝缘的整体情况提供了重要的信息.除了在硬件上采取措施抑制干扰,还可以在软件上采用数字滤波,也可以得到良好的效果.对信号采用软硬件结合的预处理措施达到满意的抑制各种噪声和干扰的效果.同时也给出了采用Maxim公司有源滤波芯片MAX274设计有源滤波器的方法.     

小波变换在抑制GIS局部放电白噪干扰中的应用

分析了GIS局部放电中白噪声干扰.仿真实验结果表明,小波分析方法抑制白噪干扰能力强,信号畸变小,能够有效的从白噪干扰中提取局放信号.     

PD雷达基本信号处理的快速原型设计方法

为了克服传统手动编写代码费时费力且易出错的缺点,本文提出了一种新的基于MATLAB/Simulink/RTW的脉冲多普勒(PD)雷达基本信号处理的快速原型设计方法.利用Simulink快速构建了一个简单PD雷达信号处理系统原型,通过RTW自动生成代码,使用Tornado将由RTW程序创建工具产生的目标文件下载到VxWorks目标CPU中,实现了雷达信号处理从系统设计、算法设计、软件开发、实时性验证各阶段工作的无缝连接,大大缩短了开发周期,提高了系统设计的可靠性,并验证了此方法在雷达信号处理中的可行性.     

PD signal propagation characteristics in GIS and its locationsystem by frequency components comparison

Propagation characteristics of partial discharge signal in GIS were investigated in a laboratory and at a 300 kV underground substation. The laboratory test indicates that signal damping can be attributed to two major mechanisms; reflection due to irregularity of characteristic impedance such as spacers, and the mode shift from TEM to TE or TM. Tests at the substation show that the signal damping phenomena are independent of propagation direction, and the mode shift gives rise to a large signal damping. The major higher mode seems to be TE₁₁ . Amplitudes of observed waveforms using narrow-band filters that agree well with the corresponding frequency components observed with a spectrum analyzer show irregular or random behavior depending upon their observation point. This indicates that narrow-band filters do not seem to be suitable for a partial discharge location system by a frequency component comparison, and the realizability of the system using broadband filters instead is discussed     

On line PD measurements and diagnosis on power transformers

On line partial discharge (PD) measurements provide information on the dielectric integrity of the high voltage insulation of oil insulated power transformers during service. These PD measurements are performed using a broadband antenna on an oil valve and UHF detection of PD signals. The sensitivity of this new detection technique is high and immunity for electromagnetic (EM) interference and corona discharges in air outside the transformer is very good. Dielectric faults can be detected in this way in an early stage of development and are classified in four categories. Automatic pattern recognition techniques of phase resolved pulse sequence (PRPS) data are very useful in risk assessment of dielectric faults.