Movement of particles in compressed SF6 GIS withdielectric coated enclosure

In compressed GIS (gas insulated switchgear), the control of wire particle contamination by dielectric coating of enclosure is demonstrated in this paper. Assuming that a particle acquires free charge through a partial discharge, the modeling of particle movement when the inside surface of a horizontal section of GIS/GITL (gas insulated transmission line) enclosure is coated is described. Under an applied 60 Hz ac voltage, the maximum height reached above the enclosure by a particle is much lower for a coated than for an uncoated enclosure. When the applied ac voltage varies, the maximum height reached depends on the magnitude of the applied voltage, phase and velocity at which the particle hits the enclosure. Typical results show that by coating the enclosure, the maximum height reached by a wire particle in a coaxial system can be reduced, thus inhibiting particle movement and minimizing the possibility of insulation breakdown     

Dynamics of metallic particle contaminants in GIS withdielectric-coated electrodes

Electrical insulation performance of compressed gas insulated switchgear (GIS) and gas insulated transmission line (GITL) systems is adversely affected by metallic particle contaminants. Dielectric coatings applied to the inside surface of the outer enclosure of a coaxial GIS/GITL system improve the insulation performance in several ways. Coating has the effect of smoothing the electrode surface and reducing the prebreakdown current in the gas gap. Also, the electrostatic charge acquired by a particle is reduced and hence the range of its motion under an applied power frequency field is inhibited. The movement of such particles is complex and dependent on several parameters. In this paper the dynamics of wire particles in a coaxial system under AC voltage is studied when the inside surface of the outer enclosure of a coaxial GIS/GITL system is coated with a high resistance material. Suggestions for reducing the particle excursion in GIS/GITL systems are discussed     

Understanding the partial discharge activity generated due to particle movement in a composite insulation under AC voltages

The UHF signals are generated due to partial discharges formed by particle movement in Gas Insulated Switchgears (GISs). It is observed that the bandwidth of UHF signals generated due to partial discharges formed by particle movement in GIS is independent of operating pressure and the applied voltage. The levitation voltage of the particle sitting on the dielectric barrier is high compared to that of it on the ground electrode. When a particle is present in between the barrier and an electrode, at certain voltage level the movement of particle will be in pseudo resonance with the applied voltage frequency. When the particle is on the barrier, on application of voltage the particle moves to the center of the electrode axis causes discharges thereby radiating UHF signals, with its dominant frequency in the range of 3–4 GHz, which is much different from that of the UHF signal generated due to partial discharges formed by particle movement. When the particle moving between the high voltage electrode and the barrier, at some time its motion get collapses and the particle settles in the low field region away from the axis of the electrode and generates UHF signals having characteristics of UHF signals generated due to corona discharge.     

Particle-triggered pre-breakdown phenomena in atmospheric air gap under AC voltage

Corona discharge mechanism and breakdown voltage characteristics of air gaps in the presence of metallic particles were investigated including the relationship between the corona discharge mechanism and the phase resolved partial discharge patterns. These results are of interest for detection of foreign particles in gas insulated systems (GIS). The results with different shaped particles show that the corona mechanism depends on the particle shape and applied voltage. Moreover the corona discharges on both sides of the particle interfere with each other by inflow of charge carriers into the particle. The breakdown voltage is a minimum when the particle is in the vicinity of the electrode due to active interference of coronas. The phase-charge characteristics as the phase resolved partial discharge patterns vary with the particle shape. This suggests that the corona discharge mechanisms for all types of particles should be considered in the particle-detection method for GIS based on the phase resolved partial discharge patterns.     

Acoustic diagnosis of gas insulated substations: a theoretical andexperimental basis

Loose particles and discharges inside the ducts of a gas-insulated substation (GIS) are considered hazardous to the insulation system. These irregularities or flaws can be detected by using acoustic sensors placed on the enclosure. An elementary review of sound propagation in a GIS together with corresponding experimental results are presented. By using ultrasonic acoustic emission sensors, an excellent sensitivity to discharges and moving particles is obtained. The method offers possibilities for quantification of the flaws, and thereby for a risk analysis. However, the degree of certainty of such an analysis is still low, especially for particles     

Insulator surface charge accumulation under impulse voltage

The surface charge distribution under impulse voltage is measured using a static capacitance probe. A probe with very small charge leakage is designed. The condition of surface charge accumulation under impulse voltage is analyzed, and it is concluded that micro discharges in the gas near the insulator surface such as the corona caused by free and fixed metal particles is usually a prerequisite condition. The dynamic equation describing the relationship between surface charge density and the applied voltage is established, and the process of surface charge accumulation under impulse voltage is analyzed. Theoretical analysis and experimental results show that the decrease of wave front time of the impulse voltage can result in an increase of surface charge accumulation. A GIS spacer is used to investigate the influence of charge accumulation on the flashover characteristics. It is shown that the 50% impulse flashover voltage can be reduced by 23.4%, and the lower limit of the V-t characteristics can be lowered drastically if the polarity of the surface charge is opposite to that of the applied voltage.     

Charging and behavior of a spherically conducting particle on a dielectrically coated electrode in the presence of electrical gradient force in atmospheric air

This paper discusses the charging and behavior of a spherically conducting particle on a dielectrically coated electrode in non-uniform dc and ac electric fields between non-parallel plane electrodes in atmospheric air. The charging mechanism of a particle resting on a dielectrically coated electrode is investigated by observing light emissions from partial discharges and by utilizing the dust figure technique. The charge acquired by a particle is estimated from the results of particle motion onset voltage measurement and direct measurement with a Faraday cage. The basic particle movement as well as particle-triggered breakdown characteristics under non-uniform electric field distribution along the electrode surface is also investigated. The results suggest that the effect of the electrical gradient force/dielectro-phoretic force on particle motion on a dielectrically coated electrode should be adequately considered in the design of gas insulated systems (GIS). This is because a particle can move laterally on the coated electrode toward increasing electric field regions by the action of the electrical gradient force which is independent of the charge on the particle. Also the possibility of the particle charging and lifting at high field regions or reaching and adhering onto an insulating spacer further increases the risk of breakdown.     

内部故障电弧下GIS母线壳体的分析及设计

为验证GIS母线壳体在发生内部故障电弧时,壳体烧穿或短路电流被开断而不会发生爆炸,笔者依据经验公式完成了GIS母线筒的结构设计,并通过ANSYS结构模块对母线筒的强度进行了计算验证,同时通过2.8 MPa水压试验完成了对母线筒强度的校核,验证了设计和理论计算分析的可靠性。另外,考虑到母线筒内电弧的运动效应,由此引起的壳体烧穿时间加长,计算分析了此种情况下GIS母线耐内部故障电弧的能力。分析的结果表明,设计的母线壳体能够满足标准要求。     

特高压GIS隔离开关操作时其壳体电压暂态特性仿真分析

特高压(UHV)系统电压等级高、容量大,电磁暂态问题相当严重。为研究特高压气体绝缘变电站(GIS)在隔离开关操作时壳体电压的暂态特性,从而对今后特高压变电站的建设及绝缘配合问题提供参考建议,结合我国某1 100kV特高压气体绝缘变电站的具体情况,分析了特高压下GIS暂态壳体电压(TEV)的计算原理,利用多导体传输线模型计算了壳体各处的TEV,并对其进行了频谱处理。最后,分析了隔离开关的操作方式、操作相别、接地方式等对暂态壳体电压的影响。仿真结果表明:隔离开关操作方式不同时,暂态壳体电压最大值出现的位置不同;在GIS出线段,由于布置的对称性使得暂态壳体电压幅值也具有对称性。     

特高压GIS变电站VFTO仿真计算研究

气体绝缘开关设备（gas insulated switchgear, GIS）中的隔离开关投切空载短母线时会产生陡波前、高幅值的特快速瞬态过电压（very fast transient overvoltage, VFTO）,对GIS及其连接的设备产生危害,严重影响设备的安全运行。通过电磁暂态程序（electro-magnetic transient program, EMTP）,针对我国“皖电东送”工程某特高压变电站开展了仿真研究,并对影响VFTO的几种因素进行分析。结果表明,母线拓扑结构和残余电荷电压对VFTO影响较大,通过合理设计隔离开关可减小残余电荷电压水平,从而显著降低变电站VFTO水平。     

气体绝缘金属封闭开关设备接地开关短路事故分析

以一起气体绝缘金属封闭开关设备(gas insulator switchgear,GIS)接地开关短路事故为例,分析事故发生的原因是隔离开关气室内金属异物在电场力和机械振动的作用下,引起盆式绝缘子沿面放电,导致绝缘破坏;在重合闸过程中,盆式绝缘子再次发生放电,电弧在气流的作用下,引起隔离开关静触头屏蔽罩与筒壁发生短路,...     

Motion and size estimation of a free moving metallic particle in GIS based on propagation properties of acoustic waves

We have investigated the propagation properties of Lamb waves and motion characteristic of free moving metallic particle in a gas‐insulated switchgear (GIS) tank to diagnose the insulation performance of GIS. We have proposed a new identification technique for defect location in GIS based on the time–frequency analysis of the Lamb waves using the Wavelet Transform. In this paper, we measured the acoustic signals excited by a metallic particle colliding with the tank sheath. Furthermore, we measured the moving particles under a high electric field in GIS using a high‐speed video camera. As a result, we examined the relationship between maximum lifting height and the flight time during subsequent impacts of a moving particle. Moreover, we estimated particle size based on the propagation properties of Lamb waves. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 150(1): 26–33, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20023     

气体绝缘开关设备中特快速瞬态过电压研究的新进展

气体绝缘开关设备（gas insulated switchgear,GIS）中的隔离开关操作空载短母线会产生陡波前、高幅值的特快速瞬态过电压（very fast transient overvoltage,VFTO）、瞬态壳体电位和电磁干扰,对GIS及其连接的具有绕组的设备、与壳体连接的二次设备绝缘产生危害,干扰二次设备工作,严重影响设备的安全运行。对2009年前国内外在VFTO测量方法、特性试验、数字仿真和对绝缘影响以及外部VFTO方面的研究状况进行了综述。概要总结了国家电网公司在特高压GIS中VFTO实测及仿真研究方面取得的新进展,提出了特高压GIS中VFTO需要深化研究的内容,即重点关注VFTO的传播特性与仿真建模,VFTO下的绝缘特性和机制研究,以期全面掌握特高压GIS中VFTO特性,对特高压输变电设备的研制、工程设计和运行提供依据和有益的参考。     

GIS母线外壳环流与暂态地电位升高现象研究

近年来GIS在电力系统的应用中体现出很大的优越性,我国电压等级较高的变电站都采用GIS形式,我国即将投建的1 000 kV变电站也采用了GIS形式.介绍了GIS母线金属外壳环流及暂志地电位升高的特性:分析了分体式连续型金属外壳产生环流的机理和影响外壳环流大小的因素,以及环流对二次设备的影响、对变电站工作人员的人身安全的威胁,并对为降低环流大小而采取的接地方式进行了讨论.     

A unique sensitivity verification combined with real-time partial-discharge identification method

The sensitivity verification with the ultrahigh-frequency (UHF) method will be discussed in this paper. The sensitivity line with the UHF method based on the conventional (IEC 60270) one is different in the radial position of the defects inside gas-insulated substation (GIS), because transverse-electromagentic mode can be more weakened while transverse electric (TE)/transverse magnetic (TM) modes can be more enhanced as the defect comes close to the enclosure than the conductor. The result makes it difficult to detect the free particle with IEC 60270. A unique sensitivity verification, which is combined with real-time PD identification method, first enables us to identify the defects and thereafter to calibrate the apparent charge of each specified defect according to the sensitivity line.     

Activity of moving metallic particles in prebreakdown state in GIS

The paper presents experimental results of measurements of prebreakdown activity, caused by free metallic particles in GIS, obtained using a phase resolved partial discharge (PRPD) analysis and acoustical measurements. The numerous parameters characterizing prebreakdown activity of particles were identified and analyzed. These included phase resolved distribution of charge, maximum charge, average charge per period, or per pulse, a balance of charge in positive and negative half-wave of voltage, pulse rate (number of pulses per period) for electrical and acoustic methods. The measurements were conducted in a compartment of real GIS, and Al as well as Cu particles of different shapes were investigated. The pressure varied from 150 to 550 kPa, however most measurements were taken at 450 kPa. A discharge model which takes into account the effect of a free metallic particle in GIS is presented     

一起363kVGIS充电闪络故障的原因分析

分析了一起363kVGIS充电时闪络故障的原因,提出了GIS交接试验中做交流耐压试验的同时应进行局部放电的测量,并在条件许可的情况下进行操作冲击电压试验,以避免如绝缘子伤痕和裂痕、自由微粒、悬浮电位和异物遗留在GIS内部等原因而造成GIS故障。     

隔离刀闸操作引起壳体暂态电位升高的数值计算与分析

为考核气体绝缘组合电器设备(GIS)在暂态下的绝缘配合和提高电力系统运行的可靠性,对由隔离刀闸操作所产生的壳体暂态电位(TEV)升高进行了研究,阐述了GIS壳体TEV的形成机理,并针对我国550 kV董箐GIS变电站由隔离开关操作产生的TEV进行了计算,分析了影响TEV的因素及TEV可能带来的危害.     

220 kV GIS设备故障消缺探讨

为查找运行中的发电变压器组甩负荷跳闸停机及GIS设备外壳被烧穿故障原因.通过查看监控系统信息、故障录波图及保护动作报文,并结合现场被烧穿GIS设备的解体检查.发现本次事故是由于GIS隔离开关动触头齿条设计不合理,隔离开关动触头转动体轴承破碎,钢珠掉落引起静触头均压环对其放电引起.针对事故原因,制定改进措施,对隔离开关动触头齿条进行设计优化改造,并提出加强对该批隔离开关运行监控的建议,将同类事故防范于未然.     

特高压交流试验示范工程GIS隔离开关带电操作试验

为验证我国特高压交流试验示范工程金属封闭开关设备(gas insulated switchgear,GIS)中隔离开关带电操作的安全性,在长治、南阳和荆门变电站对所有特高压GIS隔离开关进行了带电操作试验。在前期特高压GIS和复合型气体绝缘金属封闭开关设备(hypid gas insulated switchgear,HGIS)中特快速瞬态过电压(very fast transi-ent overvoltage,VFTO)实测研究基础上,开展现场典型运行方式下隔离开关带电操作,监测产生的VFTO和暂态壳体电位(transient enclosure voltage,TEV)。试验初步得出了特高压变电站实际VFTO和TEV水平及分布,结果表明:特高压GIS隔离开关的带电操作是安全的,但应注意产生的TEV对二次设备的影响,阻尼电阻能够有效抑制VFTO和TEV。带电操作试验的开展为今后特高压GIS隔离开关的带电操作提供了依据。