电流互感器密封失效引起的绝缘故障

首先介绍了油浸式电流互感器和SF₆电流互感器的整体绝缘结构,以近期多地出现的电流互感器绝缘故障为切入点,分析了电流互感器绝缘击穿的原因。通过电流互感器的解体检查进一步推断出设备故障的根源为互感器密封失效,针对油浸式电流互感器的金属膨胀器渗漏、SF₆电流互感器爆破片破损引发的密封失效现象,提出了运行维护建议和预防措施。     

500 kV SF6 电流互感器内部盆式绝缘子缺陷电场分析和实验研究

近年来,涉及SF₆气体绝缘电流互感器故障次数较以往明显增多。为此,对一起故障的500 kV SF₆电流互感器进行解体事故分析,发现事故是由运行过程中内部盆式绝缘子产生缺陷造成的。为深入了解气体绝缘电流互感器绝缘特性,从源头上防止突发性故障,依据SF₆气体绝缘电流互感器事故分析结果,对盆式绝缘子有气泡、裂缝、金属污染等缺陷的情况进行了三维电场仿真计算分析和局放实验研究。研究结果显示：有缺陷的盆式绝缘子电场发生畸变,尤其是有金属污染时电场畸变最为严重,局放电压急剧下降。研究得出的数据和结论为SF₆气体绝缘电流互感器的绝缘设计、结构优化、运行维护和故障分析提供了理论参考依据。     

一起500kV油浸倒立式电流互感器故障分析

油浸倒立式电流互感器应用广泛,其绝缘状况直接关系到电网安全。针对一起500kV油浸倒立式电流互感器损坏的故障,详尽阐述了故障的诊断与分析过程。首先介绍了电流互感器的基本参数和内部结构,阐述了电流互感器的故障过程和现场检查情况;然后,通过解体检查,结合系统运行工况、运行巡视情况和设备生产过程记录的核查,确定了故障发生的原因;最后,结合本次故障提出了相应的预防措施。     

一起220 kV SF6电流互感器故障的分析

SF6气体绝缘电流互感器采用20世纪90年代国际先进的倒置式结构,与传统油浸式电流互感器相比,具有绝缘特性稳定、维护简单(10～15年免维护),抗动热稳定能力强,寿命长等优点.在国内,220 kV及以上SF6气体绝缘电流互感器是近几年才发展起来的,目前其运行、试验等经验仍未成熟,故障时有发生.文中对一起220 kV SF6电流互感器故障的原因进行了分析,找出了引起故障的具体原因,并指出了当前SF6电流互感器的缺陷.     

一起油浸倒置式电流互感器故障分析及其防范措施

为了分析某550 k V油浸倒置式电流互感器发生故障的原因,对同型号同批次设备的绝缘性能进行了试验研究,结合试验后设备的解体情况和电场仿真模拟对故障原因进行了分析,并提出了相应的防范措施。结果表明,局部电场集中引起的局部放电和过电压作用造成的绝缘劣化是本次故障发生的主要原因。为有效避免此类故障的发生,需要对油浸倒置式电流互感器的出厂质量进行严格把控,同时对在运设备的绝缘性能进行定期检测,建立相应的跟踪对比数据库,并着重关注其承受过电压情况,这样可以对油浸倒置式电流互感器的绝缘劣化程度进行表征,以确保油浸倒置式电流互感器的稳定运行。     

倒置式电流互感器故障机理及诊断技术

针对倒置式SF6电流互感器和油浸电流互感器易发生瓷套断裂、爆炸、主绝缘击穿等故障缺乏针对性预防检测手段等问题,国网宁夏电科院开展了项目研究。此项目阐明了其故障机理及其预防措施,实现了嵌入式特高频局放检测及信号传输技术对倒置式SF6电流互感器绝缘缺陷的有效辨识和基于一次差分法局放检测技术对倒置油浸式电流互感器绝缘缺陷的有效检测。成果丰富了电流互感器现场检测体系,对合理设计、制造选用、安装、维护电流互感器,提高设备及电网的安全、可靠、经济运行水平,促进电气设备制造和电力生产行业的技术进步具有显著意义。     

SF6绝缘套管类设备中气体检测及运行维护

对SF₆绝缘套管类设备中气体进行检测分析有利于确保设备的安全运行。分析了SF₆绝缘套管类设备中典型放电性故障特征以及气体分解机理,并通过气体检测及现场实例分析,提出了对SF₆绝缘套管类设备的运行维护建议。     

220kV油浸式电流互感器故障分析及防范措施研究

针对一起220kV油浸式电流互感器首检期间发生的油中溶解气体数据异常情况,从电气试验、油中溶解气体分析、解体检查等方面进行分析,认为电流互感器零屏引出线根部绝缘不良,导致引出线与一次导体之间存在放电现象,是造成电流互感器故障的主要原因,由此提出相应的处理及防范措施,为设备制造商、检修及运维人员分析和处理油浸式电流互感器缺陷提供技术参考。     

500 kV SF6电流互感器的特点及结构分析

用SR气体作户外式电流互感器的主绝缘已在高压电网中得到广泛应用。SF6电流互感器与传统的油浸式电流互感器相比,在电气性能、电磁性能、热性能、机械性能、绝缘性能等方面具有显著的优点。本文对500kVSF6电流互感器的特点和结构进行了分析。     

SF6/N2混合气体绝缘特性的实验研究

目前绝大多数气体绝缘开关设备采用SF₆气体绝缘,SF₆泄漏导致严重的环保问题,人们迫切希望少采用或不采用SF₆气体,以降低对环境的污染。为此,试验研究SF₆和SF₆/N₂混合气体在不同混合比、不同压力以及在不同电场结构下的击穿特性,并与SF₆气体的绝缘性能进行比较,试验结果表明：在N₂中注入20%~30%的SF₆气体后,SF₆/N₂混合气体绝缘性能指标可以达到纯SF₆气体的80%左右,但若继续增加SF₆气体的配比,则其耐电强度上升的幅度明显变慢;此外,试验研究还发现,极不均匀电场会大大降低气体的耐击穿电压强度。试验研究证明了采用SF₆/N₂混合气体代替纯SF₆气体的技术方案的可行性。     

Comparison of SF6/N2 and SF6/CO2 gas mixtures as alternatives to SF6 gas

The interest in SF₆ gas mixtures has been re-ignited in recent years by the issue of the greenhouse effect of the SF₆ gas, and most research work is now focused on a SF₆/N₂ gas mixture, which is suitable for application in electrical apparatus with slightly non-uniform fields. This paper presents a comparison of SF₆/N₂ and SF₆/CO₂ gas mixtures with a viewpoint of their possible applications to gas-insulated transformers, where both highly non-uniform field problems and partial discharges in gas/film insulation are inevitable. It is shown that in this case the dielectric strength of SF₆/CO₂ is superior to that of SF₆/N ₂ with a minor disadvantage related to the gas decomposition in SF₆/CO₂. However, this may not be a problem for the SF₆/CO₂ gas mixture to be used in gas-insulated transformers, where internal breakdown is not allowed     

SF6/N2 mixtures: basic and HV insulationproperties

The widespread use of SF₆ by the electric power and other industries has led to increased concentrations of SF₆ in the atmosphere. This causes concern as to possible effects on global warming, because SF₆ is a potent greenhouse gas. This paper first touches on this issue and then documents the behavior of high pressure gases such as N₂ and SF₆/N₂ mixtures that can be realistically considered as acceptable intermediate or long-term replacements for pure SF₆ in some HV applications. The possible use of dilute SF₆/N₂ mixtures as an alternative to pure SF₆ for some of industry's insulation needs (albeit at higher pressure) is documented, and existing knowledge on these mixtures and on the individual components (N₂ and SF₆), both basic and applied, is compiled. A guide to existing literature is provided     

SF6/N2流注放电仿真及协同效应研究

建立反映气体放电过程中粒子运动特性的二维流体模型,采用有限元和通量校正传输法对该模型进行数值求解,计算了50%SF₆+50%N₂在均匀电场下的放电规律,模拟了流注发展过程中粒子密度的分布情况,分析放电过程中带电粒子对均匀电场的影响。搭建气体放电实验平台,测量平板电极下绝缘间隙5 mm时SF₆/N₂混合气体的击穿电压,将SF₆/N₂击穿电压的实测值与折算值进行对比,研究不同混合比、气体压强对SF₆/N₂协同效应的影响。结果表明：随着流注向阳极运动,放电间隙内的电子数密度不断增大;在放电初始阶段,空间电荷对电场的影响很小,随着电荷数量不断增加,空间电场产生明显畸变现象。SF₆/N₂混合气体击穿电压的实验测量值大于折算值,且SF₆含量越高,实测值和折算值越接近。可以看出,SF₆/N₂的协同效应在含有少量SF₆时较明显,而当SF₆含量较高时,混合气体的协同效应减弱。     

Partial discharge and breakdown mechanisms in ultra-dilute SF6/N2 gas mixtures

With the goal of reducing SF₆ gas usage, we investigated partial discharge (PD) and breakdown (BD) mechanisms in ultra-dilute (0 to 1%) SF₆/N₂ gas mixtures. The experimental results and discussions are given in this paper. In particular, we focused our research on the transition characteristics of the electrical insulation performance with an extremely small amount of SF₆ content, the PD behavior on the applied voltage, and the relation among prebreakdown streamer, return stroke and BD. Moreover, we discussed the PD and so mechanisms with reference of space charge behavior. From these results, the transition threshold at which the influence of SF₆ gas on the discharge characteristics began to appear, was clarified to be SF₆ content k=10 ppm for a total pressure of 0.1 MPa     

Fundamental insulation characteristic of high-pressure CO/sub 2/ gas under actual equipment conditions

SF₆ gas has been widely used in electrical power equipment such as circuit breakers and transformers due to its superior insulation and interruption characteristics. However since 1997, SF₆ gas has been designated a greenhouse gas subject to emission restrictions at COP3 (The 3rd session of the Conference Of the Parties to the United Nations Framework Convention on Climate Change) so a new insulating gas is needed as a substitute for SF₆ gas. This research considers the use of high-pressure CO₂ gas as an insulator while stressing the environment aspects. Fundamental insulation data for the insulating gas acquired supposing gas insulated switchgears (GIS) consists of; (1) insulation breakdown characteristics under clean conditions and, (2) insulation breakdown characteristics with metallic particle contamination. The parameters in this case were assumed from an actual apparatus viewpoint, to be a high gas pressure up to 2.0 MPa, an electrode size capable of determining the surface area effect, the electrode surface roughness, and metallic particle length, etc. at the base electrode of the 72 kV GIS. As a result, experiments using these parameters revealed insulation characteristics for high-pressure CO₂ gas and that negative lightning impulse decided the insulation design, as well as the present SF₆ GIS. The need for taking measures to suppress PD under AC voltage and also the need for restricting metallic foreign particles around the central conductor and insulating spacer were recognized     

Sulphur hexafluoride-A complex dielectric

Some of the factors that must be taken into account in designing with SF₆ are discussed. These factors include the effect of field inhomogeneities on the electrode which reduce the dielectric strength in SF₆ and the effect of SF₆ decomposition byproducts on the materials used in SF₆-insulated systems. Homogeneous and inhomogeneous field breakdown are discussed, and typical causes of failure in SF₆-insulated systems are examined. Many oversimplifications are used in the discussion, mainly to avoid having to define precisely the circumstances to which the assertions apply. In general, the system under consideration has been designed for a 30-year life, as is typical for a utility apparatus     

CF4/CO2混合气体工频击穿特性的试验研究

SF₆是目前电气设备中广泛使用的气体绝缘介质,但其产生的温室效应对环境影响极大,因此,研究能替代SF₆的环保型气体绝缘介质具有重要的意义。CF₄是一种具有低温室效应指数（global warming potential, GWP）和低液化温度的强电负性气体。通过工频击穿试验,研究了CF₄/CO₂混合气体的工频击穿特性,并对其协同效应和GWP值进行分析。结果表明：CF₄混合比为50%的CF₄/CO₂混合气体的绝缘强度能达到纯CF₄的90%左右,同时GWP值低,具有用于气体绝缘的潜力;CF₄/CO₂混合气体的协同效应值在0.12~0.38,表现出明显的协同效应。     

Applicability of simple expressions for electrical breakdownprobability increase in vacuum and gas

Simple analytical expressions for the law of breakdown probability increase are suggested. They are tested by comparing with experimental data obtained by impulse and DC breakdown. The pressure 10^-4 Pa and interelectrode gaps d<0.1 mm are used for vacuum, and the pressure 1 bar-5 bars and the interelectrode gaps 1 mm-50 mm are used for gas breakdown. The insulation gas was a SF₆, N₂ and gas-mixture: SF₆-N₂. It is concluded that such a simplified approach is not appropriate for vacuum. It is also concluded that, for gas, the BPI (breakdown probability increase) law, in the form of a simple expression, is valid in the considered range of relevant experimental parameters