GIS直线与L型结构中电磁波传播特性的仿真研究

本文使用有限时域差分法(FDTD)对由局部放电产生的电磁波在GIS典型结构(直线型和L型结构)中的传播特性进行了仿真研究。通过设置不同的电磁波激发方向、对比不同测量角度的信号时域和频域特征、以及比较两种结构的仿真结果,获得了TEM波和TE模波在直线型和L型结构中的传播特性,以及L型结构产生的反射波特征。仿真结果表明,影响电磁波传播的因素主要包括电磁波激发方向、模波速度色散和模波模式转变等。     

Resonance characteristics and identification of modes of electromagnetic waves excited by partial discharges in GIS

Electromagnetic waves are used for detection of partial discharges (PD) in GIS (gas‐insulated substations). A very wide frequency band up to 1.5 GHz is utilized for detection. There are three categories of electromagnetic wave which can be excited and propagate in coaxial cylindrical structures like GIS, namely, TEM, TE, and TM modes. The characterization and identification of each mode is indispensable to understanding the partial discharge phenomena in GIS. In this paper, peaks in the frequency spectrum excited by PD are identified in each mode and the resonant characteristics of each mode are studied. The following are the major results: (1) The resonance peaks appear at the frequencies defined by the spacer distance. (2) The intensity of each mode depends on the position of discharge source along the radial direction. The lower‐order modes including TEM are excited when a discharge source is located near the center conductor. On the other hand, higher‐order modes are excited when the discharge source is at the enclosure surface. (3) The experimental profile of each mode excited by PD along the radial direction approximately agrees with the general theory of electromagnetic wave propagation in coaxial cylindrical cavity. © 2000 Scripta Technica, Electr Eng Jpn, 131(2): 1–11, 2000     

Partial Discharge Diagnosis Method Using Electromagnetic Wave Mode Transformation in Actual GIS Structure

The diagnosis algorithm using ultra high frequency (UHF) method with the higherorder electromagnetic wave (EM-wave) was examined as the advanced partial discharge (PD) diagnosis method in a gas insulated switchgear (GIS) in the former paper. Previous studies evaluated the characteristics of EM-waves propagated in a simple coaxial cylindrical pipe, or through an L-shaped or a T-shaped pipe formed by combining these. In the present study, components (a hand hole, a post-type spacer, etc.) present in an actual GIS structure were identified, and an evaluation done mainly through an analysis on what effects their presence has on the mode transformation of EM-waves propagated inside a GIS tank. The direction in which a GIS tank is bent is horizontal (0°) in the L-shape structure. If there is either a post-type spacer or a shield ring inside, and the signal source is in the 0° direction, the distribution of the EM-wave strength varied according to through the L-shape structure. Also in the case of a Tshaped structure, the distribution of the output after signals are transmitted through the T-shaped junction varied depending on each component. Based on these characteristics, the diagnosis algorithm for PD with higher-order mode EM-waves was improved taking into account the effects of various components existing in an actual GIS, and a PD diagnosis method more suitable for an actual structure was established.     

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。     

Electromagnetic Wave Propagation in a Coaxial Pipe GIS Model

Partial discharge (PD) detection using a UHF band signal is a well known advanced insulation diagnosis method in a gas insulated switchgear (GIS) and has been actively studied. Detailed investigation of detection principles and electromagnetic wave propagation inside the GIS tank is required for significant improvement in sensitivity and accuracy. As the wavelength of UHF-band signals is comparable to the GIS tank size, higher-order modes also appear in electromagnetic waves propagating inside at frequencies at or above a certain value, creating complicating phenomena. This study investigated these phenomena, focusing on experiments with a UHF sensor inside a coaxial pipe as a simplified model of GIS structure, while varying conditions such as sensor shape and installation position (both circumferential and longitudinal), the input method of a simulated PD signal, and the presence or absence of an insulating spacer. On the low frequency side (TEM mode only), the sensor output can be described by an equivalent electric circuit determined by the coupling capacitance between the sensor surface, the center conductor and the tank. At the cutoff frequency of the TE₁₁ mode or above, resonance phenomena appeared, which were related to the pipe length. Further, it was found that installing an insulating spacer inside the coaxial pipe shifted the resonant frequency in a manner closely connected with the spacer position's relationship to the electric field distribution inside the tank.     

Electromagnetic wave radiated from an insulating spacer in gas insulated switchgear with partial discharge detection

As a means of diagnosing partial discharge (PD) signals propagate inside a Gas Insulated Switchgear (GIS), a study for the leakage of electromagnetic waves (EM-waves) emitted from the insulating spacer was implemented. The EM-waves leaking out from the solid insulator have the resonance frequencies depend on the spacing between adjacent bolts in the direction of the flange circumference, because the leakage portion is the equivalent of a slot antenna. In this paper, using an electromagnetic analysis model which has a simulated spacer on a concentrically-shaped GIS tank, the output characteristics of the EM-waves that leaked out from the slit were analyzed under various conditions such as the spacing between adjacent bolts, the width of the spacer, the dielectric constant of the spacer and the form of the flange. Also the actual measurement by the experimental equipment used to simulate the model was implemented for comparison with the analytical results. Consequently, the optimal specifications of the sensor and the measurement method used to achieve highly-sensitive detection for practical use were summarized and proposed as well as evaluating the effectiveness of the electromagnetic analysis model adopted in this paper.     

GIS中电磁波传播特性的仿真研究

为研究UHF信号在GIS中的传播特性,采用时域有限差分法进行了仿真建模和计算。GIS内部的局部放电会在腔体中激励超高频(UHF)电磁波信号,UHF法是通过对局部放电时产生的超高频电磁波信号进行检测,获得局部放电信号的有关信息以实现对设备的绝缘状态诊断和评估。UHF法抗干扰能力较强、灵敏度高。仿真结果表明,UHF信号在GIS内传播时呈现明显的时延特性,有利于局放源的定位;UHF信号的强弱和检测点与局放源的夹角Φ有关,Φ=0°和180°时信号的能量最大;局放脉冲越陡,在GIS腔体中激励的高次模波分量越大。     

GIS局部放电的超宽频检测系统初探

针对GIS运行中存在的潜伏性绝缘缺陷,根据GIS局部放电脉冲所激发的电磁波传播特性的宽频带特诊,对一种新型超宽频带天线局部放电检测系统实验方案作了探讨.     

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     

有限时域差分法对GIS局部放电传播的分析

用特高频法测量GIS局部放电所面临的困难是无法标定出视在放电量,并且也无法确定何种因素影响特高频传感器输出信号的强弱.针对上述问题,利用同轴波导模拟GIS腔体结构,并应用有限时域差分法对局部放电辐射的电磁波在波导内传播情况进行仿真.通过仿真数据分析,找出对特高频信号能量产生影响的多种因素,如：放电位置,波导尺寸,放电电流幅值和放电源的脉冲形状.从而阐明了特高频输出信号能量与原始放电脉冲的关系,为进一步探讨GIS放电量特高频标定打下基础.     

GIS局部放电超高频电磁波的传播特性研究

SF6气体中的局部放电过程可激发产生超高频电磁波。为研究GIS中超高频电磁波的传播特性,采用时域有限差分法仿真计算GIS中超高频信号的传播特性。仿真计算表明,GIS中局部放电产生电磁波在传播过程中存在延迟现象,有利于局部放电点的定位。因GIS中存在不连续点,超高频信号在传播过程中产生衰减,通过绝缘子时平均衰减3dB,通过T型接头时最严重的支路信号平均衰减10dB,而传播过程中产生的谐振使其衰减变慢。     

气体绝缘开关中电磁波的传播特性

章对局部放电脉冲激发的电磁波在气体绝缘金属封闭开关（ＧＩＳ）同轴线中的传播特性进行了理论分析,并在实验室ＧＩＳ母线上进行了实测。结果表明,高频电磁波在ＧＩＳ母线中的谐振现象为超高频法检测ＧＩＳ中局部放电提供了有利条件,同时,可利用电磁波的传播时间对局放源进行准确定位。     

基于分布式传感器的GIS局部放电在线监测实时数据传输方式的研究

针对检测GIS(Gas Insulated Switchgear,简称GIS)局部放电的分布式传感器采集局部放电信号的数据量大,通过RS-422串口进行数据传输时间长的不足。基于GIS局部放电分布式传感器在线监测系统,采用一种最大值数据压缩算法,将高速A/D采集到的大量实时数据,有效地传输到后台监测系统,解决了分布式在线监测系统中大量数据传输的瓶颈。通过实验验证,该数据传输方式速度快,性能安全、可靠,实用性强。     

The excitation of UHF signals by partial discharges in GIS

The fundamental theory of the UHF method for detecting partial discharge (PD) in gas insulated substations (GIS) is presented. The effects of position, size, current amplitude and pulse shape of the PD source on the UHF signal can be predicted using this theory. Excitation of propagating electromagnetic waves by a PD current pulse within the coaxial waveguides formed by GIS components is explained by making use of dyadic Green's functions for the electric fields of propagating modes. Experiments with a coaxial test chamber are used to verify the theoretical predictions, and comparisons are made between measured and simulated UHF signals. Some implications for the UHF measurement of PD are discussed, together with positioning and sensitivity requirements for UHF couplers. A scheme is proposed for standardizing PD measurements made using the UHF technique     

考虑多重故障的热稳关键断面在线识别方法

受限于内外部环境影响,电网发生多重故障的概率增加,离线计算确定的关键断面在网架结构受到严重破坏时无法准确反映故障后电网的薄弱环节.为此,提出一种考虑多重故障的热稳关键断面在线识别方法.首先通过故障前后支路负载率变化量和潮流方向一致性判别,识别出故障潮流转移通道.然后依据不同故障的潮流转移特征,建立基于开断分布因子的故障...     

基于超高频法GIS局部放电监测技术的研究

对于GIS局部放电的测量,超高频法是一种较为有效的方法。将频谱仪设置为零扫描模式,采用高频窄带的方法,通过安装在GIS内的超高频传感器获得的局放信号可以通过相位解析的方法表征其局放的点波波形。笔者给出了GIS中几种不同绝缘缺陷的点波波形及其指纹图。通过点波波形及指纹图,可以识别GIS中不同的绝缘缺陷类型。     

L型及T型气体绝缘开关模型中电磁波传播特性的仿真研究

采用有限时域差分方法对L型及T型气体绝缘开关(gas-insulated switchgear,GIS)模型中电磁波的传播特性进行仿真计算,分析L型及T型结构GIS中电磁波的分布及其对自身传播特性的影响。研究表明,受速率色散特性的影响,在GIS腔体的直线部分,随着接收点远离激励源,接收电磁波信号的峰-峰值呈衰减分布,但总体能量变化不大。对于L型及T型结构的GIS,在经过L型及T型结构后,信号能量衰减很大。信号频域分析表明,在0°方向存在横电磁波和横电波的11型模波TE11、21型模波TE21和31型模波TE31等高次模波,而在90°方向只存在横电磁波和T21型模波,且信号频率分量的不同导致在不同接收方向上信号能量的分布也会有差异。     

On-site measurement for the development of on-line partialdischarge monitoring system in GIS

This paper deals with the results of field tests carried out to develop an online sensor for monitoring partial discharges generated in the GIS. It covers noise distribution in the GIS tank, the propagation of partial discharge pulses, and its mechanisms, while presenting applications of partial discharge online monitoring sensors     

110 kV XLPE电缆GIS终端局部放电检测技术综合应用

对深圳电网一起典型的110 kV XLPE电缆GIS终端局部放电异常,通过综合采用基于超高频-超声波术的GIS局部放电检测技术和基于电磁耦合分离诊断的高压电缆局部放电检测技术,精确定位该电缆GIS终端局部放电是由内锥绝缘子缺陷所致,并指出此缺陷是产品质量问题,且由于出厂试验时局部放电项目漏检而成为隐患。因此,对高压交联电缆终端产品出厂检测提出了改进建议。     

基于超高频法的GIS局部放电在线监测研究现状及展望

文章综述了基于超高频(UHF)的气体绝缘组合开关设备(GIS)绝缘在线监测近年来所取得的进展，包括在UHF传感器、GIS中UHF电磁波的传播特性、局部放电源识别和定位等方面取得的研究成果，并指出了UHF在线监测系统及其应用中存在的问题，如检测频带的选择等。最后还对未来UHF局放监测的研究方向进行了展望，指出新型传感器及快捷方便的定位方法等依然是研究的重点。