直流电压下冰棱尖端放电实验研究(英文)

由于冰凌尖端和覆冰绝缘子表面之间的放电情况与覆冰绝缘子闪络电压紧密相关而引起了高度的关注,在冰凌和冰板模型基础上,通过实验研究了直流情况下冰凌尖端电晕放电现象。研究结果发现:冰凌到覆冰绝缘子表面间距、环境温度、冰水电导率对起晕电压有一定的影响,其影响原因也被逐一分析;揭示了电晕放电发展过程,在不同电压极性下,电晕放电对冰凌尖端的影响不同;当环境温度为?5℃,不同电压极性下冰凌尖端起晕电压与普通电极情况不一致,这种情况希望得到更多的证实。研究结果将会提升对覆冰绝缘子放电的理解,并有助于防止闪络情况的发生。     

Space charge behavior in SF6 gas and sequentialgeneration of PD pulses

We observed time-resolved partial discharge (PD) characteristics under ac and dc conditions in order to demonstrate the effects of space charge behavior and the corona stabilization effect in SF₆ gas. From the experimental results, we found that the charge magnitude of the first PD in the positive half cycle of applied ac voltage depended only on the instantaneous voltage. Under dc conditions we found that the magnitude of the PD charge related closely to the time interval between PD pulses. Space charge behavior and the PD generation mechanism are interpreted diagrammatically, and we describe how positive ions reduce the magnitude of PD charge and activate the corona stabilization effect and that the negative ions shorten the time interval between PD pulses     

冰凌针-板间隙直流正极性下起始电晕特性的研究

覆冰是电力系统的严重自然灾害之一。覆冰绝缘子伞裙间隙未桥接时,冰凌尖端的放电是影响绝缘子闪络电压的主要因素之一。选择冰柱-冰板间隙模型,借助于紫外线成像仪等设备,在人工气候室内研究了冰凌-冰板模型的电晕特性,提出了用紫外线成像仪确定冰凌-冰板起晕电压的方法, 分析了影响冰凌起晕电压的因素。结果表明:冰凌-冰板间隙起晕电压与冰凌状态有关,湿冰的起晕电压较低,干冰的起晕电压较高;间隙较长,起晕电压较高;气压较低,起晕电压较低;冰凌起晕电压与覆冰水电导率没有明显关系。     

气压对直流正极性下冰柱-冰板间隙电晕放电的影响

为进一步了解低气压下覆冰对绝缘子的危害,该文选择冰柱-冰板间隙模型,借助数据采集卡、紫外线成像仪和自行设计的电流传感器等设备,在人工气候室内研究低气压下冰柱-冰板模型的电晕放电特性。文章分析了气压对冰柱-冰板间隙的起晕电压、平均放电量和冰柱尖端处的放电区域等方面的影响。结果表明：起晕电压随着气压的降低而降低,平均放电量和冰柱尖端处的放电区域均随着气压的降低而减小,同时,在较低气压下,起始放电更容易形成辉光放电,放电测量也更困难。     

Corona discharge from a grounded needle electrode inserted into a charged droplet cloud

The discharge occurring in a space-charge cloud was investigated by using a cloud of charged droplets. To produce a charged cloud with a definite space charge density and to cause a reproducible discharge, droplets ejected from an airless nozzle were induction charged and transported by air flow. The transportation of charged droplets by air flow was found to be quite effective in increasing the charge on the droplets and the charge density. Corona discharge was observed at a grounded needle electrode inserted into a charged droplet cloud with a charge density not exceeding 13 μC/m³. In negatively charged droplets, positive streamer coronas occurred. As the charge density of the cloud increased, the time interval of streamer pulses decreased and the discharge shifted to a glow corona. In positively charged droplets, the height and frequency of negative corona pulses increased with the charge density and the velocity of the charged droplet cloud. © 1998 Scripta Technica. Electr Eng Jpn, 122(4): 1–7, 1998     

低气压下直流正极性冰电极电晕特性研究

覆冰将改变绝缘介质的放电过程，导致电力系统绝缘性能下降，为深入研究覆冰绝缘子串中空气间隙的电晕放电特性，基于冰棱-冰板电极系统，通过脉冲电流传感器和紫外线成像仪CoroCAM IV+揭示了气压对起晕电压、放电模式、放电波形及其幅值等的影响。通过数学分析提出表征不同大气压下不同间隙长度时起晕电压的修正公式，分析和讨论气压对放电脉冲及其幅值的影响。理论分析表明，随着气压的降低，覆冰空气间隙起晕电压呈幂函数或指数函数降低，特征指数同间隙长度相关。试验结果与理论分析一致，进一步揭示了覆冰环境下电晕放电的特性。     

冰棒—冰板间隙负极性电晕起始放电特性

国内外研究结果表明,绝缘子覆冰过程的一个显著现象是:在带电情况下,其表面冰凌并未完全桥接,而是在伞裙间形成一定的冰棱空气间隙。为研究这种空气间隙对放电发展的影响,利用冰棒-冰板空气间隙放电模型在人工气候室内进行了负极性直流电晕放电试验,并分析了不同间隙距离、不同大气压、不同覆冰类型(包括冰的表面状态以及覆冰水电导率)情况下的电晕起始放电特性。研究结果表明:随着空气间隙长度的减小和气压的降低,负极性电晕起始电压也明显下降;湿冰时的电晕起始电压高于干冰时的电晕起始电压。这些研究结果为进一步深入开展覆冰电极系统的电晕放电机理和覆冰绝缘子闪络研究打下了基础。     

表面电荷积聚对冲击电压下绝缘子沿面放电的影响

绝缘子的表面缺陷会导致表面电荷积聚，使绝缘子表面的电场发生畸变，影响冲击电压下绝缘子的沿面放电。研究了表面电荷对绝缘子沿面放电进程的影响，发现表面电荷积聚可以降低绝缘子沿面放电的起始电压。外施冲击电压的极性与绝缘子表面电荷极性是否相同会影响绝缘子的电晕起始时刻、由流注向先导的转变时间间隔和流注电晕电流。表面电荷对GIS支撑绝缘子的50％冲击闪络电压和伏秒特性也有一定的影响。     

A phase-related investigation of AC corona in air

A computer-based partial discharge detector has been used to measure AC corona pulses in air in a point-cup electrode system. The pulse height distribution was measured as a function of phase angle and pulse height for a range of voltages. The onset voltages for both positive and negative half-cycles are the same, and significantly lower than for the DC case, due to space charge effects. In all other respects the patterns for the two half-cycles are different: pulses only occur at the onset voltage (rising) for the positive half-cycle, but continuously for the negative half-cycle, except for the higher applied voltages which exhibit a glow discharge transition near the (negative) peak. Differences between the distributions for avalanches and streamers increase as the breakdown voltage is approached. Qualitative explanations of the patterns and behavior are given, together with calculations showing that space charge from one cycle can linger in the gap between half-cycles.     

Influence of voltage and load current on dc bipolar corona pulses

Digitizing oscilloscopes were used to observe anode and cathode corona pulses on a laboratory scale HVDC bipolar transmission line. Data was collected with the transmission line energized at a nominal voltage of ±60 kV with no load current. The effects of increased voltage and added load current were then separately investigated. Histograms show distributions of corona pulse amplitude and time between consecutive corona pulses (corona pulse time separation). Increasing the transmission line voltage had the effect of increasing corona pulse amplitude and decreasing corona pulse time separation for both anode and cathode. Addition of load current decreased the corona pulse amplitude and increased the corona pulse time separation for the anode. The cathode corona pulse amplitude and pulse time separation decreased with the addition of load current     

Negative DC corona discharge effects on the ultraviolet photon count in rod to plane air gaps

In order to investigate the effects of negative DC corona discharge on ultraviolet (UV) photon count, a corona discharge measurement system based on rod to plane air gaps was established. The variations of positive ion, negative ion, and electron densities were calculated with a fluid model, and the generation process of photons during negative corona discharge was investigated. The differences of photon count and the variation of charged particles between negative and positive corona were also compared. The corona current, Trichel pulses, and corona‐generated photons were measured with increasing applied voltage. An approximate parabolic relationship found to exist between the photon count and the corona current, and also an ideal quadratic function was found to exist between the photon count and the frequency of Trichel pulses. These results provide a solid foundation in the application of UV imaging detection of negative DC corona discharge in power equipment. © 2015 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

邻近直流导线时交流电晕电流脉冲特性试验

本文搭建交直流并行线路电晕放电试验平台,研究邻近直流电压时交流单点电晕放电下的电晕电流脉冲特性。并对交流电晕电流脉冲的分布模式、重复频率以及波形等特征参数进行统计分析。试验结果表明,邻近的正极性直流电压会促进交流负半周电晕放电而抑制交流正半周电晕放电,邻近的负极性直流电压作用正好相反。直流电压对交流负半周电晕电流脉冲波形参数无明显影响,而正半周电晕电流脉冲的幅值会随负极性直流电压的增加有所升高。同时发现,随着交流电压幅值的升高,促使其正半周发生电晕放电所需要的负极性直流电压幅值也相应地升高,并基于电晕放电的发展过程中电离强度的计算提出种子电子的缺失是造成该现象的原因。最后,在电晕放电离子云模型基础上,提出脉冲序列发展的过程中电离区域电场强度恒定不变的假设,从而对邻近直流电压影响下的交流电晕电流脉冲波形参数特性给出了合理的解释。     

不同海拔下电晕笼分裂导线起晕电压的计算分析

为了研究海拔高度对电晕笼分裂导线起始电晕电压特性的影响,建立电晕笼钢芯铝绞线起始电晕电压的计算模型,并开展相应试验研究。采用模拟电荷法计算钢芯铝绞线的空间电场强度。依据极不均匀电场下自持放电判据,建立不同海拔高度电晕笼分裂导线电晕起始电压的计算模型。在超/特高压人工环境气候试验室内,以500 m海拔高度为间隔,系统开展19~4-000-m海拔高度范围内六分裂导线起始电晕电压的试验研究。试验获得超高压电晕笼不同海拔高度下6-LGJ—400/50、6-LGJ—500/45分裂导线的起晕电压。计算获得不同海拔高度、分裂间距、导线分裂数及绞线表面粗糙系数下的导线起晕电压曲线族,以及不同绞线半径及最外层铝绞线股数的表面粗糙系数计算结果。分析结果表明:计算模型能够较好地计算电晕笼内绞线的起晕电压;在350~500-mm分裂间距范围内,分裂导线起晕电压随着分裂间距的增大而降低,随着导线分裂数的增加而升高;绞线表面粗糙系数与绞线最外层铝线半径与绞线半径之比相关。     

空气中电晕放电与绝缘液体中流注放电的测量和分析(英文)

Insulation is one of the most important parts in a high voltage equipment.There are gaseous,liquid and solid insulations which are commonly used.In a high voltage transformer for example the insulating materials are all used.During operation of a high voltage equipment high electric stress may occur.Under extreme condition failure of the insulation may take place.Excessive electric field in air may cause corona discharges while in liquid insulation discharges may take place in the form of streamer.This paper reports experimental results on the corona and streamer discharges in air and silicone oil.The discharges were artificially generated around a needle tip in a needle-plane electrode system with gap length of 4 mm under sinusoidal and triangular voltages.The needle was made of steel with tip radius of 3 μm and curvature angle of 30°.The needle was made by Ogura Jewelry.The discharge pulses were measured using personal-computer based partial discharge(PD)measurement system with sensitivity of better than 0.5 pC.The system is able to measure discharge in time sequential.Phase-resolved analysis of the discharges was done to interpret the physical processes behind the discharges.The experimental results showed that corona discharges took place at negative half cycles.The discharges were concentrated around 270° of phase angle of applied voltage.The discharge magnitude and discharge number of corona clearly dependent on the instantaneous of applied voltage.These were strongly supported by the application of triangular voltage.Streamer discharges occurred at both positive and negative half cycles.The discharges pulses concentrated around the peak of applied voltage at phase angle of 90° and 270°.Experimental results under sinusoidal and triangular voltages revealed that streamer discharge magnitude as well as probability of occurrence was strongly dependent on the instantaneous applied voltage.     

Particle-triggered pre-breakdown phenomena in atmospheric air gap under AC voltage

Corona discharge mechanism and breakdown voltage characteristics of air gaps in the presence of metallic particles were investigated including the relationship between the corona discharge mechanism and the phase resolved partial discharge patterns. These results are of interest for detection of foreign particles in gas insulated systems (GIS). The results with different shaped particles show that the corona mechanism depends on the particle shape and applied voltage. Moreover the corona discharges on both sides of the particle interfere with each other by inflow of charge carriers into the particle. The breakdown voltage is a minimum when the particle is in the vicinity of the electrode due to active interference of coronas. The phase-charge characteristics as the phase resolved partial discharge patterns vary with the particle shape. This suggests that the corona discharge mechanisms for all types of particles should be considered in the particle-detection method for GIS based on the phase resolved partial discharge patterns.     

空间介质颗粒对交流导线电晕特性影响规律

为了研究空间介质颗粒对导线交流电晕特性的影响,基于小电晕笼,应用Fi Lin?6紫外成像仪记录存在介质颗粒时模拟导线交流电晕放电发生、发展的过程,实验结果表明:空间介质颗粒会对导线交流电晕发生、发展过程产生影响,球径越大、距离导线越近则导线的起晕电压越低;存在多球时,由于颗粒间的相互影响,导线的起晕电压和放电过程会受到影响,其中垂直排列的颗粒之间对放电发展过程和起晕电压影响相对较大。将偏心偶极子模型应用到存在介质颗粒时电场计算中,结合模拟电荷法对导线周围存在颗粒时空间电场分布进行分析,仿真结果表明:导线表面的最大场强以及导线和颗粒间场强的均值随着颗粒尺寸的增大、颗粒导线距离的降低和颗粒相对介电常数的增大而增大;空间存在多个颗粒时,由于球间的相互影响使导线表面场强进一步增大,其中球间连线和电场方向一致时的影响更大。     

AC particle-triggered corona discharge in low pressure SF/sub 6/ gas

This paper deals with AC particle-triggered corona discharge as a follow-up to our previous research with DC voltage to clarify the particle-triggered corona discharge process in SF₆ gas. Corona current pulses, charges associated with a corona current pulse, and corona light pulses were observed with an aluminum ellipsoidal particle suspended in a parallel plane electrode system under a SF₆ gas pressure range of 30 kPalesPles50 kPa by changing the particle position. Corona mode, phase (Phi)-charge (q) characteristics as well as corona discharge processes were discussed and the following results were obtained. AC corona mode depended on the instantaneous applied voltage, voltage gradient as well as the particle position and then, the Phi-q characteristics were also affected by those parameters. Charges flow into the floating particle due to coronas on the both tips of particle and excite field fluctuations around the opposite side of particle in addition to the applied AC field. The field fluctuation in SF₆ gas by the corona charges was about 4% of the applied field and much lower than that in air gap which was about 70%. That is, the corona development was suppressed effectively by high electron affinity of SF₆ gas even in the case of floating particle. The less effective interference between coronas on the both side of particle in SF₆ gas results in an obscure local minimum in the breakdown voltage characteristics as the particle is in the vicinity of electrode as contrasted with a drastic fall in the breakdown voltage by the particle in air     

覆冰220kV四伞裙复合绝缘子电场分布仿真分析

针对国内外缺乏对覆冰220kV四伞裙复合绝缘子电场分布研究的现状,利用Ansoftmaxwell有限元分析软件模拟分析了不同冰凌长度、均压环参数和位置对220kV四伞裙复合绝缘子电场分布的影响。结果表明：（1）湿冰状态下冰凌与伞裙间隙1 mm时,冰凌桥接复合绝缘子不会发生放电现象,非桥接且系统过电压时有放电危险;（2）均压环能够显著改善高压端与第一大伞间的电场分布;（3）均压环与金具连接点垂直距离为0 mm,外径306 mm、管径36 mm时高压端和高压端附近冰凌间隙最大场强达到较好配合。     

Positive corona in air using a point/cup electrode system

The authors have previously published some measurements of negative corona currents in air using a spherically-symmetric point/cup electrode system, and also the related simulations. In this paper the corresponding current/voltage measurements and simulations for positive-point corona, again using the highly symmetric electrode system, are described. Although the corona onset voltages are again predicted with reasonable accuracy for different point radii and air pressures, the currents are very much lower, presumably due to the effect of positive space charge accumulating close to the point electrode (since the simulations assume the absence of space charges). In agreement with this assumption, the streamer pulses are only seen at or just above the onset voltage. Only avalanches occur from about 1 kV above the onset voltage.     

The effect of humidity on the charge/phase-angle patterns of AC corona pulses in air

AC corona pulses have been measured using a computer-based commercial partial discharge detector. The pulse height distribution was measured in air as a function of phase angle and pulse height for a range of voltages using a point/cup electrode system. An earlier paper discussed the effect of space charge on the onset voltages for both positive and negative half-cycles and on the patterns obtained. In the work reported in this paper, the humidity was varied, and large changes were found in the patterns observed in both half-cycles. At high humidities the negative half-cycle corona largely ceased but a second positive corona onset appeared in the second quarter of the cycle. An explanation for these phenomena is proposed in terms of the effect of the production of negatively charged water molecule clusters. Their production results in a lower effective ionization coefficient and thus higher critical field, and their lower mobility results in a more effective negative space charge. The former reduces the positive space charge in the positive half-cycle thus allowing avalanches and streamers to develop during the second quarter of the cycle. The latter results in a stronger negative space charge during the negative half-cycle which suppresses the corona during that half-cycle.