基于SF6混合气体绝缘性能的设备补气策略研究

随着电力需求的增长和环境保护要求的提高,SF6气体的使用逐渐受到限制.SF6混合气体在一定程度上减少了SF6气体用量,目前已经在电气设备中应用.文中针对SF6混合气体在220 kV气体绝缘组合电器(GIS)中发生泄漏引起的绝缘变化展开研究,通过改变微量的气压值和混合比,探究混合气体的绝缘性能变化,分析气压、混合比因素对工频击穿电压的影响规律,获取各气压下各比例混合气体的绝缘强度曲线图,从而得到保证设备安全稳定运行的补气策略.研究发现,混合气体击穿电压的变化规律呈现出随着压强和混合比的提高,非线性程度增大的特点,并且得到了设备安全运行的混合比和气压的边界值.文中的研究可以为SF6/N2混合气体绝缘设备提供运维规程和技术标准,同时为制定混合气体的检测技术标准奠定基础.     

不均匀电场下CF_3I/N_2混合气体工频击穿特性试验

从工频击穿性能的角度探讨CF_3I/N_2混合气体替代SF6气体用于气体绝缘设备的可能性。通过工频击穿试验探究气压、混合比和电极间距三种因素对CF_3I/N_2混合气体工频击穿电压的影响,并与相同条件下的SF6/N2混合气体进行对比分析,提出使用协同效应指数C值判定混合气体协同效应类型及协同效应强弱的定量分析方法。结果表明,随着混合比、气压的升高,CF_3I/N_2混合气体工频击穿性能逐渐接近SF6气体,较高气压下的CF_3I/N_2混合气体更具有应用潜力。CF_3I/N_2混合气体工频击穿电压呈正协同效应,而且CF3I气体具有优良的自恢复绝缘性能。综合考虑工频击穿性能、液化温度和环境影响三种因素,在特定的场合下,CF3I含量为20%~50%的CF_3I/N_2混合气体有可能替代SF6气体用于气体绝缘设备。     

SF6压力对GIS典型缺陷局部放电检测灵敏度的影响

气体绝缘开关设备(gas insulated switchgear,GIS)内部气压是影响局部放电检测灵敏度的重要因素。在局部放电实验平台中构建尖端、悬浮、气隙与沿面缺陷模型,基于特高频法、高频电流法与超声法开展气压0.2~0.5 MPa下局部放电信号特征的检测实验,并对比了高频电流法和超声法局部放电检测的灵敏度。实验结果表明：气压是影响尖端、悬浮与沿面缺陷放电的关键参数,3种缺陷放电起始电压与气压成正比,同一电压下的放电幅值和脉冲次数与气压成反比;气隙缺陷放电源于绝缘层内部气泡,因此设备气压对气隙缺陷放电影响不大。高频电流法可实现不同气压下的悬浮缺陷有效检测,但未测得气隙和尖端缺陷局部放电信号;SF₆压力降低,高频电流对沿面缺陷的检测灵敏度有所提升,但仍低于特高频法。超声法可实现不同气压下的悬浮和尖端缺陷有效检测,但未测得气隙和沿面缺陷局部放电信号;SF₆压力降低,超声法对尖端缺陷的检测灵敏度提高(当气压为0.2 MPa时,超声法对尖端缺陷的检测灵敏度与特高频法相当)。     

应用于直流GIL中低混合比c-C_4F_8/N_2混合气体的绝缘特性

目前GIL中使用的气体绝缘介质均为SF6气体。SF6气体虽然具有优异的电气性能,但是全球变暖潜能值(GWP)极高,因此迫切需要找到能够替代SF6的绝缘气体。文中以混合比k(c-C_4F_8在混合气体中的体积分数)低于20%的c-C_4F_8/N_2混合气体为主要研究对象,通过调节气压(0.1~0.65 MPa)和气隙间距(1~7 mm)测量了不同混合比k下混合气体的击穿电压和闪络电压,并与纯SF6气体的击穿电压和闪络电压进行了对比分析。试验结果表明:c-C_4F_8与N2呈协同效应关系;k=20%时,混合气体绝缘击穿强度约为纯SF6气体的0.6倍,绝缘闪络强度约为纯SF6气体的0.7倍,2 h耐受电压比短时闪络电压降低了5%~10%;通过提高c-C_4F_8/N_2混合气体的气体压强或增大绝缘距离可以实现替代SF6的目的。考虑到c-C_4F_8在放电中的碳析出问题,应避免混合气体用于频繁放电的设备中。     

基于混合气体热特性的GIL氮气使用配比研究

SF₆/N₂混合气体具有绝缘性能良好、环境效益好等优点,被认为是能替代SF₆的最具发展前景的气体之一,但SF₆/N₂混合气体在不同场景下的混合比问题尚缺乏研究。文中在保证气体绝缘输电线路(GIL)绝缘水平的前提下,建立多物理场耦合计算模型,从混合气体热特性的角度出发,分析不同绝缘气体压强、负载电流和环境温度下SF₆/N₂混合比与GIL温升之间的关系,为GIL在不同场景下选择合适的SF₆/N₂混合比提供依据。结果表明：绝缘气体压强和相同压强下SF₆含量均与GIL温升呈负相关关系;设备的负载电流长期超过3 kA时,建议SF₆含量为40%～60%;设备运行在中低纬度地区时,建议SF₆含量为40%～70%,运行在高纬度地区时,建议SF₆含量为30%～40%。此外,由于设计GIL设备时考虑了安全裕度,因此通常SF<...     

管道母线(GIL)中SF_6/N_2混合气体绝缘性能的研究

文中首先对GIL中SF_6/N_2混合气体的绝缘性能进行了计算,重点关注了SF_6体积分数配比以及气体压力对绝缘能力的影响,并且研究了高落差下是否出现气体分层从而对混合气体的绝缘能力产生影响。其次,利用试验装置,对SF_6/N_2混合气体在不同配比和压力下的雷电击穿电压进行了测量,并且对比分析了试验结果与计算结果的差异。计算结果表明SF_6/N_2混合气体绝缘强度随SF_6气体体积分数增加而提高,但SF_6体积分数达到10%后,混合气体的击穿电压呈现出饱和的趋势;在高落差下,SF_6和N_2的混合比随高度的变化很微小;GIL样机的雷电冲击试验结果验证了击穿电压计算结果的正确性。     

改进的击穿模型研究c-C4F8/N2混合气体绝缘性能

从绝缘强度和温室效应指数两方面研究了八氟环丁烷(c-C4F8)混合气体的绝缘性能.建立了改进的c-C4F8及混合气体的电击穿模型,理论计算c-C4F8混合气体在不同气压、不同混合比及不同电极距离下的击穿电压,并与SF6/N2混合气体在相同条件下进行了对比.研究结果表明:理论计算与实验结果相吻合.气体混合比在30%之内时,c-C4F8/N2混合气体绝缘强度非常接近相同混合比的SF6/N2混合气体.综合考虑温室效应指数和绝缘性能,c-C4F8混合气体中,c-C4F8气体含量以10%～20%为宜.     

CF3I/N2混合气体局部放电特性实验研究

CF3I气体是SF6气体的一种可能替代,然而其较高的液化温度使其难以用在气体绝缘设备中。为此,将CF3I气体和氮气混合,通过实验研究了压强、电负性气体(CF3I或SF6气体)与混合气体的气压比值(混合比)、电极距离3个因素对CF3I/N2混合气体局部放电起始电压的影响,并与相同情况下SF6/N2混合气体的局部放电起始电压进行了对比。实验结果表明:随着混合比和电极距离的增大,CF3I/N2混合气体与SF6/N2混合气体局放起始电压的比值呈现增长趋势;气压的变化对2种混合气体局放起始电压的影响大致相同;N2能较大程度地改善纯CF3I气体对不均匀电场的敏感程度,且N2体积分数为20%的CF3I/N2混合气体液化温度为-22.35～-18.35°C,其局放起始电压为纯SF6气体的0.7倍左右。因此从局放特性角度看,混合比为20%的CF3I/N2混合气体有可能代替SF6气体被用于气体绝缘设备。     

CF_3I/N_2混合气体在不同电场下的工频击穿特性试验研究

CF_3I及其混合气体作为SF_6应用于电气设备的潜在替代物被广泛关注,该文从不同电场下工频击穿性能的角度探讨CF_3I/N_2替代SF_6气体的可行性。通过工频击穿试验探究气压、混合比、电场利用系数3种因素对CF_3I/N_2工频击穿电压的影响,并与相同条件下的SF_6及SF_6/N_2进行对比分析,使用协同效应指数C值判定混合气体协同效应类型并定量分析协同效应强弱。结果表明,CF_3I/N_2在不同电场、不同混合比下的工频击穿电压随气压均呈线性增长,随着电场利用系数的增加,其工频击穿电压随气压增长的线性增长率逐渐提高;纯CF_3I对电场的敏感度尤其高。N_2的加入,改善了CF_3I对电场的敏感度;极不均匀电场下,CF_3I/N_2混合气体在0.15MPa及以上气压呈正协同效应,协同效应明显程度整体优于SF_6/N_2混合气体。稍不均匀电场和准均匀电场下,CF_3I/N_2呈现协同效应,气压越高,协同效应越明显;混合比为30%,气压为0.3MPa的CF_3I/N_2可以替代纯SF_6应用于气体绝缘输电线路和气体绝缘开关柜等电气设备中。     

雷电冲击下极不均匀电场中SF_6/N_2混合气体的协同现象EI北大核心CSCD

近年来在气体绝缘金属封闭输电线路(GIL)中开始逐步使用低SF6混合比的SF6/N2混合气体作为绝缘介质,用以替代纯SF6气体。为了在电力设备中更好地应用SF6/N2混合气体,在极不均匀电场、正负两种极性雷电冲击(LI)下,通过实验分析研究了较低SF6混合比的SF6/N2混合气体的放电特性与协同现象,并在负极性雷电冲击下发现了反常的负协同效应。研究发现:负极性雷电冲击下,N2的击穿电压随气压的升高趋势显著高于SF6与SF6/N2混合气体,当气压超过0.3 MPa后,N2的击穿电压明显高于SF6/N2混合气体,甚至在0.5 MPa时超过了纯SF6的击穿电压,即出现了显著的负协同效应,且随着气压的升高,负协同效应明显增强;正极性下仍存在一定的协同效应,但协同效应随着气压降低而减弱,当气压低至0.2 MPa,亦出现了负协同效应。     

Impulse insulation characteristics of a composite insulation system having a wedge gap in SF6 gas

Impulse insulation characteristics were investigated in a composite insulation system having a wedge gap in SF₆ gas. The partial discharge inception voltages of wedge gaps with various types of film were measured and compared with the calculated breakdown voltages estimated from Paschen's curve of SF₆ gas. Also discussed is how the charge accumulated on the film surface due to a partial discharge had an effect on the creepage breakdown voltage. Partial discharge inception voltages in wedge gaps were higher with higher SF₆ gas pressures and with lower film permittivities. Creepage breakdown voltages depended little on gas pressures or on creepage distances. The dependency of breakdown voltages on gas pressures and the effect of polarity on the breakdown voltage differed with the types of film. This may be partly because the charge on the film due to partial discharge had an effect on the discharge propagation, and that charging of the film differed with the types of film.     

PD time‐sequential properties of SF6 and SF6 gas mixture including CO2

This paper deals with partial discharge (PD) time‐sequential properties of SF₆/N₂/CO₂ ternary gas mixture as well as SF₆ and SF₆/N₂ gas mixture under AC and positive DC voltage applications. The measurements were carried out by changing the gas pressure up to 0.6 MPa and applied voltage with the N‐shape characteristics of breakdown voltage versus gas pressure for each tested gas considered. We obtained experimental results of the gas pressure dependence of maximum peak value of PD current pulse as well as the relationship between the time interval of PD pulses and the peak value of PD pulse. We discuss the mechanism of increase in breakdown voltage by adding CO₂ into SF₆/N₂ gas mixtures in terms of change of PD type from streamer to leader discharge. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 151(3): 32–40, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20073     

Insulation properties of a CO2/N2 50% SF6 gas mixture in a nonuniform field

This paper describes partial discharge (PD) inception and breakdown voltage characteristics of a CO₂/N₂/SF₆ gas mixture in a nonuniform field. These voltage characteristics were investigated with ac high voltage by changing the mixture rate of each gas of CO₂, N₂, and SF₆ gas and the gas pressure from 0.1 MPa to 0.6 MPa. It was found that adding a small amount of CO₂ gas into a N₂/SF₆ mixture causes a drastic increase in the breakdown voltage. For instance, when the mixture rate of SF₆ in N₂/SF₆ gas mixture is 50%, with the addition of 1% CO₂ the maximum breakdown voltage becomes 1.31 and 1.15 times higher than that of a 50% N₂/50% SF₆ gas mixture and pure SF₆ gas, respectively. Moreover, those voltage characteristics of a CO₂/N₂/SF₆ gas mixture were also investigated by changing the electric field utilization factor as well as by applying positive and negative standard lightning impulse voltages in order to discuss the corona stabilization effect, which seems to be one reason for the drastic increase in the breakdown voltage. These results and breakdown mechanism of the CO₂/N₂/SF₆ gas mixture are discussed on the basis of the corona stabilization effect and the dissociation energies of the component gases by observing PD light images, PD light intensities through a blue and red filter, and PD current waveforms. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 140(3): 34–43, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10019     

A study on hybrid insulation composition joint using gas and solid insulator for gas‐insulated power equipment

SF₆ is used as the main insulation gas for gas‐insulated switchgear (GIS), but it has recently become a gas that must be restricted because of its greenhouse effects. To date, we have studied the insulation characteristics of compressed N₂ and CO₂ as possible alternatives for SF₆. We have reported that N₂ or CO₂ must be pressurized to 2.0 MPa when it is used as a substitute for SF₆ at 0.5 MPa. Therefore, we have proposed a hybrid installation composition that uses gas and solid insulators. Because the central conductor of GIS is covered by a solid insulator in this composition, a high‐pressure gas at 2.0 MPa is not needed. However, the joint of the solid insulator becomes a weak point for discharge development. In this paper, we describe an effective configuration for improvement of the withstand voltage based on experiments. The most effective connector was made of resin without an implant electrode and the most effective configuration was one without a solid–solid interface between the solid insulator of the central conductor and the resin connector. In this experiment, the improvement of breakdown electric field of the hybrid composition was 44% or more compared with the case of only gas insulation (conventional method). In addition, further improvement can be expected by optimizing the insulation creepage distance and configuration. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 178(1): 11–20, 2012; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21107     

基于一维电弧模型的SF6混合气体灭弧性能评价

SF₆混合气体是广受关注的SF₆替代气体方案之一。为定量评估SF₆混合气体的灭弧性能,文中采用一维衰减电弧模型和玻尔兹曼方程相结合的方法,将电弧熄灭过程划分为热恢复阶段、弧前介质恢复阶段和弧后介质恢复阶段,分别引入热恢复率、弧前介质恢复率和弧后介质恢复率作为各阶段的评价参数,并计算三者的调和平均数作为综合评价参数,以此来评估SF₆-N₂、SF₆-CO₂、SF₆-CF₄以及SF₆-Air混合气体的灭弧性能。基于上述方法,文中初步探讨SF₆含量、背景气体种类和压强大小对SF₆混合气体灭弧性能的影响。结果表明,随着SF₆含量的减少,混合气体的灭弧性能整体上呈现下降趋势;当SF₆含量为10%～50%时,4种混合气体中SF₆-N₂的灭弧性能最优,其次...     

Insulation characteristics of SF6 gas for nonstandard impulse voltage polarity reversal pulse waveforms

Evaluation of insulation strength for lightning surge that actually enters into substations is important in estimating insulation reliability of gas‐insulated equipment. The standard lightning impulse voltage (1.2/50 µs) is used for factory tests. However, the actual lightning surge waveforms in substations are complex and are usually superimposed with various oscillations. Insulation characteristics of SF₆ gas as a function of such complex voltages have not been sufficiently clarified. This paper deals with gap breakdown characteristics in SF₆ gas under submicrosecond pulses. Breakdown voltages are lower under a polarity reversal condition than under a monopolarity condition. The cause of this difference is discussed while observing discharge propagation using an image converter camera. The electrode size effect is also discussed. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 146(4): 18–25, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10246     

Insulation characteristics and its evaluation method of N2 gas for nonstandard lightning impulse waveforms

Until recently, SF₆ gas has widely been used as the best insulating medium in substation equipment. However, SF₆ gas was specified to be a greenhouse gas at COP3 in 1997 because of its high global warming potential (GWP), and alternative insulation gases to SF₆ have been sought for a long time. Alternatives using the natural gases are considered to be suitable, but none of them show better properties for insulation as well as good environmental compatibility. Therefore, it is necessary to rationalize the equipment insulation level and reduce the test voltage of electric power apparatus to as low a level as possible. The actual lightning surge waveform (so‐called nonstandard lightning impulse waveform) occurring in the actual field is different from the standard lightning impulse waveform (1.2/50 μs). There are many cases in which the actual lightning surge waveform has a steep rise and large decay of overvoltage, and the insulation requirements are not as severe as those for the standard lightning impulse waveform. In this paper, we focused our research on N₂ gas as an SF₆ substitute and investigated the insulation characteristics of N₂ gas for a single‐frequency oscillatory waveform with various frequencies from 2.7 to 20.0 MHz and damping ratios. Based on the experimental results, it might be possible to reduce the test voltage of N₂ gas insulation by evaluating the crest value of the actual lightning surge waveform that has been converted into an equivalent standard lightning impulse waveform. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 167(2): 10–20, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20754     

A study on condition assessment method of gas‐insulated switchgear. part II. influence of moisture in the SF6, detection of a partial discharge on a spacer,repetition discharge and overheating by incomplete contact

Rationalization of the maintenance of gas‐insulated equipment under operation and lifetime extension based on the results of appropriate diagnosis are necessary to reduce the cost of gas‐insulated equipment. Therefore, condition‐based maintenance (CBM) is required and accurate methods for observing the inside of equipment are important. In this report, we describe a diagnosis method that can be used for actual gas‐insulated equipment, such as to assess the deterioration of the spacers made of epoxy resin and to detect loose connections in the central conductor. The principal results are summarized as follows: (1) The quantity of decomposition gases depends on the moisture and magnitude of the partial discharge. However, decomposition gases were detected even if SF₆ had low moisture content (less than 100 ppm) similar to that used in actual equipment. This means that our method can be applied to actual equipment. (2) It became clear that CF₄ is a typical gas generated by partial discharge on the spacer surface. Therefore, it is possible to diagnose spacer deterioration by monitoring CF₄. (3) Decomposition gases (SF₄, SO₂, SO₄, SO₂F₂) were generated by impulse breakdown, which was assumed to be due to repetition discharge caused by insulation failure and loose connections. (4) SF₆ gas was assumed to be exposed to a loose connection and was heated from room temperature to 800 °C, and the generated decomposition gases were analyzed by FTIR in real time. As a result, the decomposition gases were generated at temperatures above approximately 500 °C in a heating time of 1.5 minutes. Therefore, a loose connection can be detected by analyzing the decomposition gas. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 176(2): 22–30, 2011; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21108