Investigation of VFT surges propagated into transformer and overvoltages applied to winding

Investigations were conducted on the VFT (Very Fast Transient) surges that propagate into a 500‐kV transformer. The disconnector restriking surge and ground fault surged were discussed. It was regarded that a large part of the surge voltage was applied just at the entrance of the transformer winding for the VFT surges. Thus, an equivalent circuit that models the windings was used for the analysis. The overvoltages that appear between the first winding sections at the entrance of the transformer were computed. The following was established. (1) The overvoltage between the first winding sections becomes greater when the magnitude of the voltage change at the transformer terminal is larger. The overvoltage between the first winding sections is not affected by the magnitude of the transformer terminal voltage. (2) For the disconnectors that are not connected directly to the transformer, the voltage change at the transformer terminal is not so large. (3) In the case of a ground fault at the GIS near the transformer, the voltage change at the transformer terminal is the same as that for a disconnector directly connected to the transformer. (4) In actual GIS, the disconnector that is connected directly to the transformer is not usually used. In this situation, the overvoltages that threaten the transformer insulation will not be generated by the restriking of the disconnectors. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 146(2): 20–26, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10225     

Results of lightning impulse tests for a 275‐kV full GIS substation

This paper describes the outline and results of the lightning impulse tests for a 275‐kV full GIS substation. The behavior of lightning surges is a very important factor for the rational design of substations and low‐voltage and control circuits inside the substations. For the above reason, we carried out lightning impulse tests for a new 275‐kV full GIS substation. In these tests, we measured voltage induced in low‐voltage and control circuits, transient characteristics of grounding grid, injected voltage and current waveforms, and so on. By investigating these data, we confirmed the behavior of lightning surges inside the substation. We also compared simulated waveforms by EMTP analysis with the measured waveforms. The simulated results agreed well with the measured results. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 146(1): 46–58, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10230     

特高压气体绝缘开关设备中特快速瞬态过电压特性的试验研究

气体绝缘开关设备（gas insulated switchgear,GIS）中隔离开关操作产生的特快速瞬态过电压（very fast transientovervoltage,VFTO）会影响电气设备的安全运行,随着系统电压等级的提高,该影响会越来越严重,在特高压系统中尤为突出。为掌握特高压GIS的VFTO特性,在特高压GIS设备的VFTO试验回路进行了大规模GIS隔离开关操作试验,并对VFTO测量结果进行了统计分析。研究得到了VFTO全过程波形的波形特征、击穿次数、频率成份和残余电压分布,单次击穿波形的波形特征和振荡系数分布,及预充/不预充直流电压下的VFTO幅值特性,揭示了隔离开关加装阻尼电阻对VFTO的抑制作用。所获得的特高压GIS中的VFTO特性为进一步研究VFTO仿真和绝缘配合等提供了依据。     

Quantitative evaluation of lightning surge range voltage–time characteristics in high‐pressure SF6 gas

Gas‐insulated switchgear (GIS) is subjected to very fast transient overvoltages such as lightning surges or disconnector switching surges. Therefore, the sparkover voltage and time (V?t) characteristics of SF₆ in a very short time range of less than are of great interest from the viewpoint of insulation design and coordination for a GIS. This paper describes the V?t characteristics of SF₆ at a gas pressure of 0.5 MPa using a steep‐front square impulse voltage under a quasi‐uniform field gap and presents a quantitative evaluation of the V?t characteristics for a nonstandard lightning impulse voltage. In the case of a square impulse, the V?t characteristics of positive polarity were observed to be almost flat over a long time range from 80 ns to , and rose steeply over a short time range from 80 ns down to 20 ns. For negative polarity, the V?t characteristics exhibit a gentle rise from 200 ns down to 40 ns. In the estimation of V?t characteristics, the equal‐area criterion parameters were quantitatively estimated using the square impulse. For a nonstandard lighting impulse, we found that application of the equal‐area criterion with these parameters for the nonoscillating impulse and oscillating impulse of up to 5.3 MHz as a model of lightning surge and disconnector switching surge is possible. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 159(4): 8– 17, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20309     

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。     

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。     

Electromagnetic‐circuit co‐simulation of very fast transient overvoltage in gas‐insulated switches

The very fast transient overvoltage (VFTO) originating from operations of an isolating switch in a gas‐insulated switch (GIS) will cause dangerous interference to the switch and its peripherals. Aiming at the engineering issue, a collaborative simulation method by field‐circuit‐wave of VFTO radiation interference is proposed in this paper. With a combination of project cases, the GIS equivalent circuit is first extracted by means of quasistatic electromagnetic (EM) field analysis. Furthermore, the equivalent time‐varying voltage source of VFTO is obtained by associating the time‐varying resistance model of the switching arc and the broadband circuit method. Finally, using the transient full‐wave technique in the time domain, the spatial EM interference by VFTO is simulated. It turns out that this method has high significance to the high‐voltage switch design. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

官亭750kV GIS隔离开关操作时的特快速暂态过电压实测研究

论文全面介绍了3种类型(内部、外部、瞬态外壳地电位)特快速暂态过电压(以下简称VFTO)的测试系统、方法和现场测试结果。750 kV GIS内部VFTO测试的一次传感器采用设备自带的内部传感器,二次传感器采用自主研制的高频响应同轴传感器;瞬态外壳地电位测试的采集系统采用高频TEK高压探头的测试设备。这两种类型VFTO测试采集系统均配备高频响应的阻抗变换器、光纤传输系统、记录系统等远距离传输测试系统;外部VFTO采用倒置式光纤测量原理和方法,配备所研发的整套采集、传输和记录系统。所有采集、测试系统均考虑现场测试的抗干扰设计。通过所研发的测试系统实测了750 kV官亭变隔离开关带电操作时的3种类型VFTO的测量结果,并进行了波形、数据分析,对实现750 kV和1 000 kV GIS中隔离开关正常带电操作具有重要的参考价值和指导意义。     

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。     

2.5MV特快速瞬态过电压发生器

气体绝缘开关设备（gas insulated switchgear,GIS）以其占地面积少、密封性好,受环境影响小,运行可靠、维修周期长等优点在中国电网中得到了广泛应用。在330kV以上电压等级的系统中,开关动作产生的特快速瞬态过电压（very fast transient overvoltage,VFTO）对系统有很大危害。为满足特高压GIS中VFTO的模拟,利用6MV敞开式冲击电压发生器与陡化装置结合的方法,研制出一种模拟VFTO产生的装置。通过增加GIS母线长度来补偿回路固有电感的影响,以及通过控制陡化间隙的击穿电压来控制输出电压幅值,使该装置可以输出幅值为2.5MV、高频振荡达到35 MHz的电压波,能够满足特高压试验对VFTO模拟的要求。采用外加积分器方式,制作了一种锥形电容传感器来测量该装置产生的电压波,测试结果表明该电容传感器可以满足试验的要求。     

一种限制GIS暂态地电位升高的措施

用EMTP程序对用不同的氧化锌避雷器限制GIS内快速暂态过电压的效果进行了计算,并给出了快速暂态过电压与暂态地电位升高的简单算式。同时对某GIS的隔离开关操作引起的暂态地电位升高数值进行了现场测量。提出了用氧化锌避雷器阀片限制GIS暂态地电位升高的措施。     

GIS中的快速暂态过电压及影响因素分析

在本文建议的简化等值回路进行验证的基础上,计算了某一国产GIS中隔离开关操作引起的快速暂态过电压,并对一些影响因素进行了分析讨论。     

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。     

GIS中VFTO对隔离开关气室中盆式绝缘子的影响研究

结合GIS隔离开关气室的实际结构,给出隔离开关燃弧状态的等效电路模型和参数,利用电场能量法计算了气室两端盆式绝缘子的对地等效电容值.在此基础上,对气室两端盆式绝缘子处的VFTO进行了数值仿真,提取频率和对应的电压信息,分析了在VFTO作用下盆式绝缘子的暂态电场分布,并且对盆式绝缘子发生热击穿的情况进行了研究.     

1100 kV GIS隔离开关分合容性小电流试验中的暂态电压测量

GIS隔离开关分合容性电流过程持续时间长,同时产生高幅值、大陡度、高频率的过电压。采用新研制的光纤式电压测量系统,对1 100 kV GIS隔离开关分合小电容电流试验中的暂态电压进行测量,得到了分合过程中负载电容上"台阶"状电压波形,同时采用EMTP仿真软件对电压波形进行相应的仿真研究,得到了负载上电压的幅值、频率、波形等相应特性。而且试验和仿真结果一致。证明该测量系统可以用于特高压隔离开关分合容性电流用暂态电压的测量。     

V-t characteristics of SF6 gas during lightning surges

The waveform of a standard lightning impulse differs greatly from those of actual lightning surges acting on GIS. This raises the problem of the equivalence of the standard lightning impulse. This report describes the effect of voltage waveforms on insulating performance in an SF₆ gas gap subjected to fast oscillating impulse voltages simulating actual lightning surges, and the evaluation of V-t characteristics by applying the equal area criterion. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 119(4): 1–11, 1997     

GIS中的电磁暂态现象

GIS以其较高的运行可靠性,易维护,占地面积小等优点在电力系统中得到了广泛的应用。但是,在隔离开关、接地开关和断路器的动作过程中,会出现快速暂态过程。主要表现为:GIS母线套管上的快速暂态过电压和GIS壳体上的暂态地电位升高以及GIS周围空间产生暂态电磁场。主要分析和探讨由快速暂态过程引发的暂态电磁场的产生和传播机理以及它对GIS的电缆出线和与GIS相连的变压器的影响。     

GIS电站内传导干扰计算模型的建立

为了仿真计算GIS电站内由开关操作在二次回路产生的传导干扰,提出了GIS传导干扰整体计算模型的概念,并建立了模型。在这个整体模型中,用有理函数建立了用于计算容性传导耦合的PT/CT的高频模型和用于计算阻性传导耦合的多端口地网模型。这些模型是基于实测数据采用矢量匹配法建立的。把这些有理函数模型植入EMTP后,不仅可以计算一次系统的特快速暂态过电压和暂态地电位升高,还可计算二次系统的干扰信号。     

550kV全封闭组合电器快速暂态过电压影响因素分析

分析了550kV全封闭组合电器(gas insulated switchgear,GIS)中隔离开关(disconnector,DS)操作时产生快速暂态过电压(very fast transient overvoltage,VFTO)的影响因素,提出了抑制GIS系统中VFTO的方法。以董箐水电站为研究背景,根据550kVGIS结构及运行特点,在计算了隔离开关7种操作方式下VFTO的基础上,分析了VFTO对变压器绝缘的危害与对避雷器计数器的影响以及残余电荷电压和合闸电阻对VFTO幅值与频率的影响。针对在建的特高压输变电系统,提出了抑制VFTO的措施,可为特高压GIS设备的生产与运行提供参考。     

500kV GIS隔离开关操作产生VFTO的研究

针对气体绝缘封闭式开关设备(GIS)中快速暂态过电压(VFTO)产生的原因、出现的种类、对GIS本身以及对外部设备的危害等问题,对某水电站500 kV GIS建立了系统的仿真模型,利用电磁暂态仿真软件ATP-EMTP,计算分析了隔离开关在3种典型操作方式时在主变压器线圈上引起的VFTO,并提出了防止VFTO的运行操作要求。