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。     

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。     

Study of abnormal electrical phenomena effects on GSU transformers

Three generator-step-up (GSU) transformers successively failed in a large pumped storage plant, resulting in a considerable economic loss for the utility. A comprehensive investigation was done to find out the possible failure causes. Several aspects are considered in this study, including switching transients resulting from routine switching operations, lightning overvoltages, and harmonics and spikes due to static frequency converter (SFC) operation. The study showed that circuit breaker and disconnector restriking may affect transformer insulation due to their frequent occurrence, gas insulated switching gear (GIS) side surge arresters provide inadequate lightning protection to GSU transformers, and SFC operation has little effect on transformer insulation. This paper presents the simulation results. Methods to lower the lightning transients at the transformer terminals were provided and implemented.     

雷电波侵入XLPE电缆绕组的暂态特性

利用雷电波侵入XLPE电缆绕组的外端口特性得出其暂态等值电路,并进行分析求解.发现避雷器的放电电压和残压越高,电缆绕组上的电压越高;但是侵入波越陡、入口电容越大,反而可能使得电缆绕组上不会出现高于避雷器残压的过电压,有利于电缆绕组的保护.这与传统变压器绕组出现具有余弦振荡性质的过电压有很大不同.对绕组输入模拟雷电波进行实验并使用EMTDC仿真,对比表明电缆绕组在雷电冲击电压作用时外端口特性可用R、C串联支路来近似等效.为这种新型变压器的设计、保护技术提供了参考依据.     

VFTO作用下变压器绕组的谐振分析

为了研究气体绝缘变电站中陡波前过电压对变压器的影响,以多导体传输线理论为基础、以匝为单元建立了变压器绕组的单输入多输出端口模型,并详细推导了该模型中传递函数的求解。通过对变压器绕组的幅频特性分析,研究了绕组中的谐振情况并对谐振可能发生的位置进行了定位。仿真结果与试验结果相符,说明了该方法的可行性和正确性。     

Switching overvoltages in motor circuits

The switching of HV motor circuits in the megawatt range can cause large overvoltages on motor terminals. The amplitude of the resulting voltage spikes depends on breaker type and circuit characteristics. If the amplitude of switching overvoltages exceeds the basic insulation level of the motor, overvoltage protection circuitry should be installed to prevent a motor insulation failure. The decision whether overvoltage protection circuitry (surge pack) must be installed requires a prediction of the overvoltage level. This paper deals with switching overvoltages in motor circuits with a unit transformer between switchgear and motor. Overvoltages of motor circuits were simulated using specially developed simulation models. The results of three case studies revealed a large impact of cabling and transformer on motor overvoltages. In most of the cases, a unit transformer connected between switchgear and motor will provide an overvoltage protection to the motor. However, the transformer can also be a main cause of large overvoltages when connected to cables of specific length and capacitance. The paper provides some simple rules to recognize such critical configurations     

氧化锌避雷器在并联电容器装置中的应用及参数选择

本文从分析断路器分断电容器装置过程中产生单、双相重燃过电压对电容器装置的危害入手,进一步说明氧化锌避雷器对电容器装置操作过电压的保护作用及其参数选择,文末提供应用实例和计算结果。     

天生桥—广州直流工程控制保护系统改造后的过电压分析

基于改造后的天生桥—广州±500 kV高压直流输电工程,计算分析了在换流变Y/Y线圈阀侧单相接地、交流相间操作冲击、逆变侧失交流电源和逆变侧闭锁而旁通对未解锁4种典型故障工况下的系统过电压,确保在改造后的控制保护系统下,系统各点过电压及避雷器能耗限制在合理范围内,各电气设备能安全运行。分析结果表明:换流变Y/Y线圈阀侧单相接地故障将在中性母线上产生较高过电压,中性母线避雷器能耗较大;交流相间操作冲击会在阀两端产生较大过电压,阀避雷器动作;逆变侧失交流电源会在逆变站交流母线产生较高过电压,交流母线避雷器动作。逆变侧闭锁而旁通对未解锁会在逆变侧直流极线产生很高的过电压,直流极线避雷器能耗较大。上述4种故障工况下,各避雷器能耗均未超过设计通流容量,避雷器能安全稳定运行。     

氧化锌避雷器在并联电容器装置中的应用及参数选择

本文从分析断路器分断电容器装置过程中产生单、双相重燃过电压对电容器装置的危害入手,进一步说明氧化锌避雷器对电容器装置操作过电压的保护作用及其参数选择,文末提供应用实例和计算结果.     

Switching surge overvoltages on the feeding system of a MAGLEV train

This paper investigates switching surge overvoltages due to a section switchgear between coils and a feeding cable, and surge overvoltages due to a ground fault in the feeding cable. The maximum overvoltage due to switchgear closing is about 25 kV on the coil and 15 kV on the cable sheath. The coil overvoltage becomes greater as a source voltage reaches its peak. The overvoltages due to switchgear breaking is dependent on the breaking current and they reach 115 kV on the coil and 15 kV on the cable sheath when the current is 50 A. The fault surge overvoltage is about 24 kV on the coil which is smaller than the switching overvoltage. On the other hand, the cable sheath overvoltage reaches 32 kV, which is the largest among various overvoltages investigated in this paper, and could result in sheath insulation breakdown. The coil overvoltage due to current breaking by a section switchgear may cause coil insulation breakdown when the breaking current is large. Both the coil and sheath overvoltages can be controlled to less than the insulation level by arresters. © 1998 Scripta Technica, Electr Eng Jpn, (4): 58–66, 1998     

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。     

Analysis of transient surge transmission characteristics of electronic circuits due to arc discharge generated with disconnector on/off in GIS

In gas‐insulated switchgear (GIS), the arc discharge due to a disconnector on/off generates fast transient surges, which can be the cause of malfunction and damage to electronic devices such as microprocessors and AD converters, if the fast transient surge exceeds a specified level. In this paper, it is shown that the comparison and evaluation are realized between the measured results and the calculated ones of fast transient surges generated due to a disconnector on/off in 300 kV GIS by adopting the evaluation index. The calculation is carried out by applying the authors' proposed equivalent circuits using distributed constant lines in consideration of the structure of GIS and a newly developed divided‐type voltage sensor. Also, it is found by using the evaluation index that the measured results and the calculated results are in good agreement with each other. Furthermore, the cause of the occurrence of the peak of the evaluation index is clarified by analyzing the equivalent circuit. And the signal conditioning using a low‐pass filter for electronics circuits connecting the divided‐type voltage sensor is designed. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 149(2): 34–42, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10360     

天生桥—广州直流系统换流阀过电压机制研究

基于天广500 kV高压直流输电工程,分析了阀过电压产生的机制,结果表明,在以下2种情况下阀两端会产生较大过电压:1)最上层换相组的阀全部关断后,在该层换流阀两端可能产生严重过电压,而其他几层阀关断时一般不会在阀两端产生过电压;2)交流相间操作冲击将在阀两端产生较大过电压。据此对换流变高压端Y/Y绕组阀侧单相接地和交流相间操作冲击2种典型故障进行了仿真分析,结果表明:当直流系统以最小输送功率运行时,整流站换流变高压端Y/Y绕组阀侧单相接地故障在阀两端产生较大过电压,通过阀避雷器的能量最大,但随着输送功率的增加,能量会减小;整流站的换流变变比要比逆变站大,因而相同幅值的交流相间操作冲击在整流站换流阀两端产生的过电压相对严重。     

High‐frequency voltage oscillation in transformer windings and electrical breakdown properties of interturn insulation immersed in oil at VFT voltage

Switching operations in gas insulated switchgear (GIS) can generate very fast transient overvoltages (VFTO) which propagate in the GIS with little attenuation. When a transformer is directly connected to the GIS through a gas/oil bushing, the VFTO can enter the transformer and excite the voltage oscillation in the windings. In the paper, we firstly show a resonance phenomenon due to the superposition of the traveling waves which was found in the experiments using the coil windings of a 500 kV transformer. The fundamental resonance frequency ranged at about 2 MHz, and its voltage at the interturn (turn‐to‐turn) of the coil could reach 0.25 times of the applied voltage in the worst case. Secondly, the electrical breakdown properties of interturn insulation in oil were studied, applying the unipolar and bipolar voltages with 2 MHz oscillatory frequency. The breakdown voltages at the unipolar and bipolar VFT oscillatory stresses were about 1.25 and 1.40 times higher than that at the standard lighting impulse, respectively. We discuss the experimental breakdown stresses with the ones estimated from the analysis of VFTO in the transformer windings and also show the methods to cope with the VFTO. © 2000 Scripta Technica, Electr Eng Jpn, 132(4): 45–52, 2000     

Insulation coordination for delta connected transformers

It is common practice to install only phase to ground surge arresters for transformer insulation protection against electrical stresses. However, this may not adequately protect the delta connected transformer phase to phase winding insulation. High phase to phase overvoltages at the transformer terminals, due to capacitor switching, have been reported. This paper describes the excessive phase to phase overvoltages that can also occur due to wave propagation and surge transfer through transformers. This paper points out the need for surge arrester arrangements that protect both phase to phase and phase to ground transformer insulations. Surge arrester arrangements, selection criteria, installation practices, and application considerations are discussed in this paper     

1000kV变压器绝缘水平的探讨

1000kV变压器是特高压交流输电工程最关键的设备之一。文章对1000kV变压器3个绕组(高压绕组1000kV,中压绕组500kV,低压绕组110kV)之间的过电压和绝缘配置进行了深入探讨,以期进一步完善特高压系统的绝缘配置、改善特高压变压器抵御过电压的能力和运行工况。推荐了1000kV变压器500kV绕组高性能避雷器的参数,可为降低变压器500kV绕组的绝缘水平、改进特高压变压器的结构设计及提升容量等提供参考。     

锥形绕组特快速暂态过电压分布研究

为了研究在陡波前、高重复频率的电压冲击下,脉冲变压器(PT)锥形绕组中的特快速暂态过电压(VFTO)分布特性,建立了基于多导体传输线(MTL)理论的PT二次绕组分布参数模型;利用锥形绕组结构上的特性,提出一种有限元法(FEM)和插值公式相结合的方法以快速计算锥形绕组的感应系数矩阵K;通过求解频域下的电报方程可得到绕组的对地电压分布以及匝间电压分布;进行了绕组暂态电压的测量,从实验结果可以看出电压分布的一定规律,并分析了造成计算与实验结果间误差的原因;结合实验提出一种改善电压分布的措施,对大功率PT二次绕组的绝缘设计有一定的参考意义。     

试验研究VFTO作用下层式绕组暂态特性

为了研究特快速暂态过电压(VFTO)对层式绕组绝缘的影响,设计制作了分段层式绕组试验模型,该模型分为4段,每段5层,以每1层为1个单元,共分20个单元。试验过程分别对该分段层式绕组模型中有铁心和无铁心注入VFTO脉冲电压信号,并采集记录了入波后分段层式绕组模型各个单元节点电压信息,通过各节点电压信息分析了分段层式绕组模型暂态电位分布情况,并根据入波电压和响应电压求出分段层式绕组电压传输函数的幅频特性,分析了分段层式绕组中谐振频率情况。试验研究结果为层式绕组的绝缘结构设计提供了理论依据。     

GIS中VFT过电压数值分析简化模型的构建方法

为计算GIS隔离开关操作引起的快速瞬变过程 (VFT)的电压波形 ,首先通过分析各个GIS构件的几何形状、尺寸及空间布置情况 ,结合多年来VFT行波的相关研究结果 ,并按照不能明显影响VFT基本波形和过电压幅值的原则 ,简化了影响VFT波形的各个GIS构件的精确模型。其次 ,以一个由母线、隔离开关、接地开关、断路器、电流互感器、电压互感器和套管等组成的典型GIS单元电路为例 ,检验了模型简化方法的有效性 ,简化模型的构建将有助于分析VFT过电压的形成机制 ,以指导GIS的结构设计     

基于暂态过电压下行波分析的变压器绕组变形在线故障定位方法

绕组变形是变压器内部的主要故障类型之一,严重威胁电力系统正常运行。为有效提高绕组变形在线检测的准确性,结合变压器在运行中遭受暂态过电压冲击的特性,提出基于暂态过电压下行波分析的变压器绕组变形在线故障定位方法。当暂态过电压信号侵入变压器绕组时,在绕组末端获取电压行波信号,采用具有自适应白噪声的完整集成经验模态分解方法(Complete Ensemble Empirical Mode Decomposition with Adaptive Noise,CEEMDAN)对其进行分解,得到本征模态分量(Intrinsic Mode Function,IMF),计算各IMF分量下的相关系数,对比分析后选取一些IMF的相关系数作为绕组变形的故障特征量,最后结合BP神经网络构建故障特征和故障点的映射关系,实现绕组变形的在线故障定位。仿真结果验证了本方法的可行性。