负极性直流电压下棒-棒间隙和绝缘子的雾中放电特性

为了深入研究空气间隙和清洁直流绝缘子在雾条件下的放电规律,进一步探讨污秽外绝缘受雾影响的特性,开展了棒-棒空气间隙和清洁绝缘子在雾条件下的负极性直流电压放电特性试验。选取0.5、1.0 m棒-棒空气间隙和6片绝缘子串3种试品,对比分析了其在干、雾条件下的负极性直流闪络电压Uav和闪络电流。随后通过改变试验室内的气压,探索了海拔高度H对棒-棒空气间隙和清洁绝缘子闪络电压的影响。试验结果表明,0.5 m和1 m棒-棒空气间隙在雾条件下的Uav比干条件下的分别高22%和23.6%,雾条件下的气压特征指数n与干条件下的基本相同,0~2 000 m范围内,H每升高1 000 m,Uav降低10%~11%;而绝缘子串的Uav在雾条件下比干条件下低,其雾条件下的n为0.39,小于棒-棒空气间隙的n。研究结果可供直流雾中放电研究和高海拔地区直流输电工程外绝缘设计参考。     

确定气体绝缘击穿电压的统计方法

§1 引言对于空气间隙(或绝缘子),为了衡量它们的绝缘能力,需要知道间隙的击穿电压(或绝缘子的闪络电压)。然而由于气体击穿具有一定的分散性,对同一个间隙,我们重复多次试验,每次所得结果并不完全相同。表1列出了1米棒—板间隙工频击穿电压     

空气间隙和绝缘子在直流电压上叠加冲击电压放电特性的试验

本文给出在+100kV、+200kV、+400kV和+500kV直流电压上叠加操作冲击(250/2500μs)或雷电冲击(1.2/50μs)电压的放电试验结果。试验是在棒—板间隙、支柱绝缘子以及悬式绝缘子上进行的。试验结果可供HVDC输电线路和换流站设计者参考。     

特高压直流线路复合绝缘子悬挂方式对其冲击闪络特性的影响

V串绝缘子在输电线路中得到了广泛应用,但其与I串绝缘子的冲击闪络特性差异尚不明确。为此,在特高压工程技术(昆明)国家工程实验室开展了V串和I串悬挂方式的±800 k V复合绝缘子在操作冲击和雷电冲击作用下的放电试验,并通过有限元仿真软件对2种悬挂方式下复合绝缘子附近的电场分布进行仿真分析。结果表明:当有效绝缘距离相同时,正极性冲击电压下的V串绝缘子50%冲击放电电压低于I串绝缘子,而负极性冲击电压下的V串绝缘子50%冲击放电电压高于I串绝缘子;V串缘子下均压环与横担间的空气间隙的电场分布更接近棒–板间隙,而I串绝缘子2个均压环间的空气间隙的电场分布更接近棒–棒间隙。因此,I串和V串绝缘子间冲击闪络特性的差异是由于电极结构的极性效应引起的。     

220kV线路悬式绝缘子串异物临近放电机制研究

为研究玻璃绝缘子串在鸟粪和鸟巢材料(异物)下落时的放电机制,用铁丝模拟异物进行了试验研究,首先开展了异物临近时间隙放电试验,基于对不同铁丝长度和空间布置时放电电压的测量和放电路径的观察,分析了放电机制。研究表明:当足够长的铁丝临近绝缘子串时,放电过程仅是铁丝上下两端空气间隙的击穿过程;当较短的铁丝临近时,放电过程为空气间隙击穿和绝缘子沿面放电的混合。然后开展了铁丝与金具电极间隙放电试验,基于对不同间隙长度下放电电压的测量,分析了间隙放电特性,研究表明铁丝–金具间隙与典型的棒–棒间隙击穿特性相似,理论计算中取平均击穿电压梯度为4.0 kV/cm。最后建立了实际线路和试验布置的三维有限元模型,研究异物临近对绝缘子串周围电位和电场分布的影响,将仿真计算得到的放电电压与实际试验电压进行对比,验证了试验结果的准确性。放电机制、试验和仿真结果可为输电线路杆塔涉鸟故障风险区域划定提供参考依据。     

高海拔地区500kV输电线路用复合绝缘子与并联间隙的绝缘配合

为丰富并联间隙用于在高海拔环境下500kV电压等级线路的绝缘配合研究,在2 100m海拔下对不同结构的500kV输电线路复合绝缘子用并联间隙进行了冲击击穿特性试验,并比较了不同结构并联间隙冲击击穿特性的差异。同时,根据雷电冲击试验和操作冲击结果,参考绝缘子串与并联间隙的绝缘配合原则,得到了合适的并联间隙间距。研究结果表明:3 780mm棒形并联间隙、3 780mm环形并联间隙2种并联间隙适合2 100m海拔的500kV线路工程运用,可满足保护绝缘子及线路绝缘的双重要求。研究结论可为并联间隙的工程设计提供支持。     

500千伏线路绝缘避雷线用绝缘子保护间隙的电气选型试验

500千伏晋京线的绝缘避雷线经绝缘子及并联间隙接地,要求在正常运行条件下,绝缘避雷线绝缘子、并联间隙的工频放电电压必须大于避雷线上的感应电压;在雷电冲击波的作用下,保护间隙击穿且流过导线与避雷线间的电容电流时,保护间隙应可靠地熄弧。为了电网的安全运行,并为设计和安装提供依据,测量了绝缘子在各种状况下的电导、电容;试验了绝缘子和保护间隙的工频干、湿闪放电电压和保护间隙的灭弧性能。选择XDP—7C型绝缘子作为绝缘避雷线用的绝缘子,并根据试验重新设计了保护间隙。     

600～4200千伏冲击电压发生器系列产品介绍

<正> 上海电缆研究所根据自行研制的4200千伏、220千焦冲击电压发生器近十年实际运行所取得的经验,研制开发了600～4200千伏冲击电压试验成套装置的系列,以满足高压电力电缆(包括附件)、高压电器(包括开关、避雷器、变压器、互感器、套管)和外绝缘(棒-板、棒-棒空气间隙、绝缘子串、支柱绝缘子)进行雷电冲击和操作冲击电压方面试验     

雨水对外绝缘特性的影响

介绍了在海拔高度为３６４８ｍ的高压实验室内,用正、负雷电冲击电压及工频电压对绝缘子串、棒——板间隙进行干、湿放电特性研究的结果。得出了绝缘子串干、湿闪电压与串长及棒——板间隙干、湿放电电压与间隙长度的关系。对影响绝缘子串湿闪特性的原因进行了分析。     

重污少雨环境下长棒形瓷绝缘子积污特性

长棒形瓷绝缘子在重污秽、少降雨环境下积污严重,存在污闪隐患。为此选取长棒形瓷绝缘子用量较大、年平均降雨较少的徐州市,在岱姚5667线d级污区悬挂长棒形瓷绝缘子和盘型瓷绝缘子,对比少雨积污期内的自然积污差异;采用人工积污试验和积污仿真模型,研究长棒形瓷绝缘子的积污特性。结果表明:2016年2—4月的自然少雨环境中,长棒形瓷绝缘子各月平均积污量都大于盘型瓷绝缘子,两者的等值盐密比约为3.4:1;风洞模拟的积污环境下,长棒形瓷绝缘子LP75、LP85的等值盐密、灰密均大于盘型瓷绝缘,芯棒直径较小的长棒形瓷绝缘子积污更多;仿真结果表明,受开放伞型结构的影响,污秽颗粒在气流作用下更易与长棒形瓷绝缘子表面发生碰撞。在重污少雨环境下,长棒形瓷绝缘子自洁性难以体现,应及时清扫。     

A Study of Early Discharges in Air Gaps

The corona pulses appearing in air gaps under high-voltage impulses are the bases for the complete discharge in these gaps. The various elements affecting the creation of these pulses and their consequent influence on flashover are investigated. The delay of corona pulses and the probability of their occurrence are related to those of breakdown. The results are used to form design grounds for the air insulation of high-voltage apparatus. The experimental work was performed on 50-cm rod plane air gaps at the High Voltage Laboratory of Cairo University.     

Review of research on nonstandard lightning voltage waves

Although the impulse insulation level of a power apparatus is specified under the standard 1.2×50-μs voltage wave, the apparatus seldom encounters such a voltage wave in the field. A wealth of knowledge exists on the behavior of air gaps under nonstandard lightning impulse voltages. The objective of the Task Force was to compile a bibliography on the nonstandard lightning impulse voltages and review the present state of research. This paper reviews the present status of research including the behaviour of air gaps under transient voltages, and the generation and measurement of fast-front impulse voltage waveforms     

A new technique to improve the dielectric strength of a multi-dielectric insulation system

In this study, an attempt is made to improve withstand-ability of the multi-dielectric medium by the effect of an additional electric field in the transverse direction to the main applied electric field. High voltage HV insulation system is chosen in this study is an air-solid insulation system. In this study, two types of gaps are used simultaneously: the first one is the main tested gap MG, and the other is the transverse gap TG. The MG consists of two parts: part one is air insulation, and part two is solid insulation. The transverse field is applied to part one, i.e., air gap of the MG. According to the results extracted from this work, the flashover voltage of the dielectric medium two increases as the transverse voltage TV within the region one increases whereas the conduction current of the MG decreases as the TV increases. Moreover, the effect of TV increases as gap pressure decreases. Actually, the effect of TV is much marked in low vacuum gaps than in atmospheric air gaps and compressed air gaps. The improvement in flashover behaviors in the presence of a transverse electric field illustrates a marked dependence on the item of pressure; the type of transverse applied electric field (AC or DC), and the transverse field plane level. However, the improvement does not depend on the specimen material. In addition, it is worth mentioning that this improvement in the flashover behaviors of solid dielectric in the region two is related fundamentally to the process of lowering electric stress in the region one of the MG.     

高温气冷堆核电站主氦风机驱动电机绝缘系统评定技术研究

设计了一套在0.1 MPa氦气和空气环境下测试绝缘系统电气绝缘性能的试验装置,完成了0.1 MPa气压下氦气和空气中主氦风机驱动电机绝缘系统模型的局部放电起始电压(PDIV)、起晕电压、匝间冲击、绝缘电阻和工频击穿电压对比试验。试验结果表明:在0.1 MPa气压下,绝缘系统在氦气环境下的部分绝缘性能较空气中大幅下降,氦气环境下绝缘系统的PDIV值约为空气中的50%,起晕电压值约为空气中的20%~25%,闪络(击穿)电压约为空气中的50%。     

沙尘对电力系统外绝缘电气特性影响分析

为了解沙尘对电力系统运行造成的影响,在查阅有关文献的基础上分析了沙尘对空气间隙和绝缘子放电特性的影响,同时在沙尘模拟实验室进行了风沙对间隙击穿电压影响的实验研究。分析和研究表明:在雷电冲击和操作冲击电压作用下,沙尘对空气间隙的冲击放电特性有一定的影响,主要是由于阴极表面上的沙尘引起;沙尘对空气间隙及绝缘子放电特性的影响程度与风速、沙尘的带电量等因素有关。     

Correction factors for positive dc voltages

Direct-current voltages are used mainly to test equipment utilized in HV dc transmission systems, as an alternative to ac for testing cables, capacitors, insulations in which internal discharges may lead to degradation of the insulation under ac testing conditions, in investigations in discharge physics and dielectric behavior. For atmospheric air the voltage measurements under any conditions are related to the standard conditions employed in the IEC-60 standard. It is demonstrated that the IEC correction procedure is not adequate for dc voltage measurements at high altitude; for example for rod-plane gaps there is a difference >10% between experimental data obtained at 2240 m above sea level and those corrected with the IEC-60 procedure. This is mostly a consequence of the fact that the physical model employed, which is based on the field of propagation of streamers, fails to account for the combined effect of humidity and altitude. It is surmised that the propagation field of the prebreakdown streamers varies linearly with the air-density. The experimental rod-plane results obtained by the authors are better modeled by an alternative semi-empirical model     

基于人工神经网络的变压器绝缘模型放电模式识别的研究

分析了变压器绝缘的主要放电形式,设计了模拟变压器放电的7种试验模型和3种模拟空气中放电干扰的模型,进行了不情况下模型的放电试验。使用数字化测量装置,取得了各种模型放电的放电量－相位信息。采用三维谱图提取放电指纹特征,并用人工神经网络ANN来识别不同的放电类型。研究结果表明,人工神经网络对油纸变压器绝缘放电有足够的识别能力。     

±500 kV同塔双回线路杆塔空气间隙操作冲击放电特性试验研究

在海拔2 100 m和50 m地区对±500 kV同塔双回线路杆塔空气间隙的操作冲击放电特性进行试验研究,在实验条件下,获得了上、下层间隙的50%放电电压曲线,验证了下横担的存在对上层空气间隙的操作冲击放电特性无明显影响。基于两种海拔高度试验结果对比,提出了海拔2 100 m及以下地区的海拔校正方法和校正系数,进而给出了当操作过电压标幺值取1.6时,不同海拔高度下所要求的杆塔上、下层空气间隙的最小允许距离。成果已用于指导溪洛渡右岸电站送电广东±500 kV同塔双回直流输电工程的外绝缘设计。     

带并联间隙地线复合绝缘子直流覆冰闪络特性

架空地线融冰已成为一个亟需解决的问题,目前通常对架空地线进行改造加装带间隙的绝缘子并采用直流融冰,其融冰电压受到地线绝缘子放电电压的制约,进而也影响了地线融冰的长度。对耐张型和悬垂型两种地线绝缘子在严重覆冰条件下并联间隙大小与地线绝缘子直流冰闪电压间的关系进行了试验研究。结果表明:两种地线绝缘子表面清洁、未覆冰情况下,其直流50%放电电压U50%与并联间距d呈幂指数关系,随着并联间距d增大,U50%增大,且增速逐渐减小;覆冰条件下,耐张型并联间隙地线复合绝缘子并联间距的选择与覆冰厚度di相关,可以选为(10+2di)mm;悬垂型地线绝缘子在严重覆冰地区建议选择80~100mm的并联间距。在保证融冰期间地线与杆塔保持良好绝缘的条件下,应选择较小间距来提高其防雷性能。     

Switching impulse strength of air insulation: leader inceptioncriterion

The author introduces a general criterion for leader inception of phase-to-ground air insulation under positive critical switching impulses. This criterion established the correspondence between continuous leader initiation in the vicinity of the highly stressed electrode and conditions prevailing later at the instant of the final jump. The criterion is applied to several complex electrode configurations, including rod-rod, conductor-rod, and conductor-structure gaps, where both analytic and digital techniques are used to compute the leader inception voltage, 50% breakdown voltage, and gap factor. The theory has been systematically tested against available experimental results with quite satisfactory agreement