污秽绝缘子表面电场分布仿真及绝缘特性试验

In this paper,the electrical fields along the insulator surface under different scenarios,such as asymmetric pollution on top/bottom surface,and uneven circumferential distribution of surface pollution,have been calculated with finite element method for field simulation.Tests on artificial pollution insulators are conducted to study the 50% withstand voltage U50 of artificial pollution suspension insulators under different NSDD(non-soluble deposit density)and asymmetric pollution on the top/bottom surface,and study the change of leakage current with air humidity under different voltage and different ESDD(equivalent salt deposit density).The result shows that asymmetric top/bottom surface pollution has a greater impact on the insulator electrical field distribution,and the leakage current will jump under low air humidity,if had large ESDD,which has practical meanings to the anti-pollution design of the transmission line under different pollution levels across the country.     

高海拔地区±800kV特高压直流线路复合绝缘子悬挂方式对污闪电压的影响(英文)

To solve the contamination flashover problem for transmission lines in high-altitudes area,an analysis of the flashover performance of contaminated ±800 kV ultra high voltage(UHV) DC composite insulators of various suspension modes at a high altitude(2 100 m) is presented.The 50% withstand voltage(U50%) was determined by the up-and-down method.Experimental results show that suspension modes play an important role in the flashover performance since DC arcs detach from the insulator surfaces more easily at high altitudes than at sea level.Flashover voltages of the long string composite insulators gradually decreased with salt deposit density(SDD).The flashover voltage of type II string is by 4.6% lower than that of type I string.For type V string,the ionized air could more easily diffuse away from the insulator surface,while producing a higher utilization ratio of the leakage distance.Therefore the flashover voltage of type V string is by 8.7%～14.4% higher than that of type I string.Type Y string configuration appears to lead to much lower flashover voltages than type I and V string configurations.     

基于非线性时间序列分析的绝缘子污闪预测研究

To solve the problem of the flashover forecasting of contaminated or polluted insulator,a flashover forecasting model of contaminated insulators based on nonlinear time series analysis is proposed in the paper.The ESDD is the key of flashover on polluted insulator.The ESDD value of insulator can be forecasted by the method of nonlinear time series analysis of the ESDD time series and a forecasting model of polluted insulator flashover is proposed in the paper.The forecasting model consists of two artificial neural networks that reflect relationship of environment,ESDD and flashover probability.The first is used to estimate the ESDD time series of insulator and the second is employed to calculate the probability of the flashover.A series of artificial pollution tests show that the results of the forecasting model is acceptable.     

A Forecasting Method of Pollution Flashover Voltage of Insulators Based on Robust Regression

In view of the limitations in the prediction of pollution flashover voltage by least squares regression, a method to predict pollution flashover voltage by robust regression is proposed. According to testing voltage and the data of salt deposit density (ρSDD ) and non-soluble deposit density (ρNSDD ), the regression coefficient is solved by a complex weighting least square iteration algorithm. In iterative calculations, the weight function is adopted, in which the weight coefficient is the function of the residual error of last iteration to weaken the influence of singular values on the regression coefficient. The characteristic exponent denoting ρSDD influence and characteristic exponent denoting ρNSDD influence are mapped by the regression coefficient, and thus the pollution flashover voltage of insulators can be predicted. Through the comparison of test results, robust regression results and least squares regression results, the effectiveness of the proposed robust regression-based forecasting method is verified.     

±1000kV特高压直流输电系统设备电晕特性(英文)

Corona performance is an important factor should be taken into consideration in power transmission project designs.Power equipments operate in various environments which will affect their corona inception voltages and thus influence the operation safety of transmission systems.In this paper,corona characteristic tests of bus bars,shielding rings,simulated eight-bundled conductors,and insulators were carried out in areas with different altitudes up to 4 300 m.Simulation tests of environmental factors were carried out in a HVDC corona cage.Based on site tests,it is concluded that corona inception voltages of both bus bar and shielding ball increase with their height to the ground or their dimensions.The influences of water droplet,wind,icing and surface contamination on corona inception voltage were also obtained from the simulation tests.The corona inception voltage of mist is higher than that in saturated water droplets.Conductivity of precipitation has little impact on corona discharges.Corona inception voltage decrease with increasing wind speed.The influence on corona current of glaze is the biggest,and that of hard rime is more than that of soft rime.The impact of pollution material on corona discharge depends on the size of pollution particle.Test results obtained in this paper are solid reference for design of UHV DC transmission projects.     

特高压直流输电系统多换流站共用两个接地极的优化设计(英文)

Ultra high voltage direct current(UHVDC) electrode sites choosing become more and more difficult due to the limited land resource,and it results in an urgent requirement of common electrode technology.The optimized designing method of two kinds of electrodes commonly used by multi converter stations is studied in this paper.The performance criteria and the rational jointing style between electrode lines and electrodes are analysed and determined at first,based on which,the mathematical model of the two kinds of electrodes is established,and an inequality equation set is formed to satisfy the relative standards of environmental impact on ground electrodes.Consequently the optimized designing method is presented through simplification of the model.After all,a specific example is given based on the parameters of Southwest Hydroelectric Project in China,in which two electrode sites had been pre-chosen.The results show that,tens of plans of the two kinds of electrodes together with their electrode performances can be provided based on the presented method.The errors of current distribution ratio in all the examined plans are maintained about 1%,the maximum error of earthing resistance is 7% and the maximum error of step voltage is 4%,which prove the engineering practicality of the method.     

风沙条件下的平板模型直流沿面放电特性

The influence of sand dust on discharge of external insulation has caused widespread concern.At present,the research results show wind-sand electricity has a remarkable effect on the discharge characteristics of insulator and has little influence on the discharge characteristics of air gap.The flashover of insulator strings occurs along the insulator surface and air gaps,and the sand dust deposited on the insulator surface may affect the flashover characteristics of insulator strings.This paper studies the flashover characteristics of flat plate model under DC voltage in wind-sand condition.The experimental results show that under positive polarity voltage,the flashover voltage of the flat plate model has a maximum value,while under negative polarity voltage,the flashover voltage of the flat plate model has a minimum value with a certain degree of sand dust deposition.The wind or sand in sand-dust weather has an important effect on the flashover characteristics of the flat plate model.In certain variation range of electric charge,electric charge of sand dust has little effect on the flashover voltage of flat plate model under DC voltage.The deposition of sand has significant influence on the flashover process of flat plate model,which is related to the deposition density and moisture content of sand particle.     

Radiated Electromagnetic Field Signature of Cracked and Polluted Porcelain InsulatorsEI北大核心CSCD

Porcelain cap and pin insulators are by far the most popular suspension insulators in high voltage （HV） dis- tribution networks all around the world. Inspection and condition monitoring of HV insulators is also very important to the utility companies because of the critical and vital role that they play in distribution systems. In terms of safety, practicality and ease of use, remote detection methods are more popular among the line technicians. A new remote condition assessment method based on electromagnetic radiations from porcelain insulators is presented in this gaper. In a lab environment, a string of two porcelain insulators is energized by a 45 kV transformer. Electromagnetic radia- tions due tO the partial＂discharge activities inside the porcelain insulator are captured by passive sensors and antennas. Two cases of defective insulators on a two insulator string are studied here. The first case focuses on the effect of con- taminated porcelain shells on radiation signature of partial discharges. A polluted porcelain shell with ESDD level of 0.03 mg/cmz was first tested. The second case studies the effect of cracks of an intentionally-cracked porcelain shell. The cracked insulator is also tested on a two insulator string. To compare the partial discharge radiation signature of different faulty insulators, phase resolved graphs were developed. The electromagnetic radiated signature of a polluted insulator and a cracked insulator was＇calculated and compared using phase resolved graphs.     

基于ATP-EMTP的±500kV直流线路雷击事故仿真分析(英文)

This paper calculates and researches on lightning accident of ±500 kV Xing-An DC transmission line in Guangdong based on ATP-EMTP and the simulation calculation model of the HVDC has been constructed. The results show that: when a lightning current strikes to the positive polar conductor of double circuit transmission line and the flashover of insulator strings occurs, as the over-voltage wave propagating along the lines due to the coupling effect between the conductors, the grounding electrode lines would produce the coupling voltage wave, which makes the flashover of the insulator strings occur at the different place along the grounding electrode lines, the unbalanced current of the grounding polar line is produced due to the insulator strings flashover and the unbalanced current exists for a long time, when the unbalanced current is up to the locking condition, the negative polar conductor is locked and the double-pole block fault occurs. In the paper, some effective measures are given to prevent this accident.     

交直流复合电压下的油纸绝缘局部放电统计图谱研究(英文)

The converter transformer is one of the most critical equipments in high-voltage direct current transmission systems.Valve-side windings have to withstand complex stresses combined of AC,DC,and pulsed voltages.Partial discharges(PDs) can thus easily occur in oil-impregnated paper insulation.The current paper presents the statistical phase-resolved distributions of partial discharges in oil-paper insulation under combined AC and DC voltage stress.First,the voltages in the converter transformer were analyzed.In the experiments,four artificial insulation defect models were designed to generate PD signals under AC-DC combined voltage stress detected by a Rogowski coil sensor.Histograms including the φ-q-n data of these PD signals were created.The variations of φ-q-n data generated by PDs in different insulation defect models were analyzed while increasing the test voltage.Experimental results showed that the PD phase-resolved distributions of different insulation defect models were different from one another.The findings of the current study are useful in further research on the mechanism and pattern recognition of PDs in converter transformers.     

35～1000kV线路绝缘子污闪电压值的估算

针对目前绝缘子污闪电压缺乏系统研究的现状,建立了35~1 000 kV输电线路用普通型绝缘子交流污闪电压的计算模型即展开普通型绝缘子成平面模型后分析交流污闪条件,计算出绝缘子在不同表面污层电导率条件下的临界污闪电压值;对35~1 000 kV输电线路用5种不同吨位的普通型绝缘子进行交流人工污秽试验,获其在各盐密下的50%污闪电压;通过计算值和试验值的对比,可将绝缘子表面污层电导率转化为盐密,从而算出各普通型绝缘子在不同盐密下的交流污闪电压值。试验验证计算结果误差小,说明该模型能够有效估算代表普通型绝缘子的50%污闪电压情况。该研究结果可供各电压等级输电线路外绝缘选择参改。     

人工污秽下盐/灰密对普通悬式绝缘子串交流闪络特性的影响

污闪是电力系统的严重自然灾害之一,国内外对盐密(ESDD)的影响进行了大量的研究,但对灰密(NSDD)影响的研究较少。文中以7片串普通悬式绝缘子XP-160为试品,在人工雾室中进行了大量的人工污秽试验,分析了ESDD和NSDD的变化对人工污秽绝缘子交流闪络电压的影响。试验结果表明:在人工污秽试验中,ESDD和NSDD均对绝缘子交流闪络电压有影响,与ESDD对人工污秽绝缘子串绝缘子交流闪络电压的影响一致,人工污秽绝缘子串交流闪络电压与NSDD也呈幂函数关系。在对交流闪络电压的影响上,ESDD和NSDD是相互独立的。因此,污区的划分不仅应考虑ESDD,同时也应考虑NSDD。对于7片串XP-160,文中还给出人工污秽试验条件下绝缘子串的交流污闪电压表达式。     

基于泄漏电流脉冲主成分分析的外绝缘污秽状态评估方法

为了防止污闪事故的发生,需要对外绝缘污秽状态进行评估。本文提出一种基于泄漏电流脉冲主成分的外绝缘污秽状态评估方法。首先对一种常用悬式绝缘子进行人工污秽试验,利用泄漏电流测量系统记录不同等值附盐密度(ESDD)和不同相对湿度(RH)下的电流波形,根据脉冲阈值的不同,将泄漏电流脉冲分成80档。利用主成分分析,从中提取一组泄漏电流脉冲主成分向量,用于概括原80档脉冲包含的信息。聚类分析和综合主成分分析的结果表明,绝缘子泄漏电流脉冲主成分向量与污秽度之间存在密切的关系,可以为外绝缘污秽状态评估提供重要参考。     

盐密和灰密对110kV复合绝缘子闪络电压的影响

合成绝缘子具有很好的防污闪特性,但也会发生污秽闪络,这与常规的人工污秽试验仅考虑盐密的影响不无关系。文中选择110kV合成绝缘子为试品,在人工雾室中研究了灰密(NSDD)和盐密(ESDD)对合成绝缘子污闪特性的影响,分析了NSDD影响的原因,并采用2种方法对试验数据进行了分析和拟合。结果表明:人工污秽试验中,合成绝缘子污闪电压Uf与ESDD和NSDD均有关,但二者的影响是彼此独立的;随着ESDD或NSDD的增加,其Uf均按幂函数规律降低;ESDD和NSDD对Uf影响的特征指数分别为0.106、0.140,即对于合成绝缘子,灰密的影响大于盐密,这与瓷绝缘子相反;灰密对污闪电压影响的原因之一是吸收更多的水分,二是破坏合成绝缘子的憎水性。     

基于BP人工神经网络的绝缘子等值附盐密度预测

等值附盐密度是确定污秽等级和绘制电网污区分布图的主要依据,但是,它易受测量用水量的影响,且测量只能在停电状态下进行.通过对3种常用悬式绝缘子进行人工污秽试验,采用BP人工神经网络的方法,建立了以泄漏电流最大值、泄漏电流5个脉冲主成分、环境湿度、温度等8个变量作为输入参数,等值附盐密度作为输出参数的智能预测模型.使用Levenberg-Marquardt快速学习算法对建立的神经网络进行训练.其试验数据验证了该方法的可行性.     

饱和受潮条件下的绝缘子泄漏电流特性

空气湿度的大小直接影响到绝缘子表面污层的润湿情况,进而影响泄漏电流的特性。为此,针对目前电力系统大量使用的多种绝缘子,采用固体污层法试验研究了绝缘子在饱和受潮条件下的泄漏电流特性。在简要介绍了试验装置后详细分析了泄漏电流与染污程度、受潮状态、爬电比距等因素的关系,并建立了泄漏电流最大值与等值盐密、污闪电压梯度、运行电压、绝缘子串长、雾浓度之间的对应关系。这些基础规律的研究,可为绝缘子泄漏电流监测系统的正确预警和专家系统的正确分析奠定基础。     

浸污法试验不溶物质对绝缘子污闪电压的影响

绝缘子表面不溶物质的类型和量对其污闪电压有影响,然而在以往人工污秽试验中常忽略这种影响。为此用人工污秽试验研究了不溶物质种类和灰密的影响。试验结果显示:浸污法试验中同一盐度的污液中硅藻土灰度不仅影响绝缘子表面的灰密,且对绝缘子表面的盐密和污闪也有很大的影响,随着硅藻土灰度的增加,绝缘子上盐密增大,其50%闪络电压下降,50%闪络电压与硅藻土灰度呈幂指数关系;同样的盐密下,随着灰密增大,闪络电压减小;不溶物质的种类对污闪电压有影响,不溶物质为高岭土的闪络电压比不溶物质为硅藻土的低。     

基于BP人工神经网络的绝缘子泄漏电流预测

外绝缘泄漏电流和绝缘子的污闪过程存在密切的对应关系，相对湿度是影响泄漏电流产生和发展的关键因素之一。首先对两种常用悬式绝缘子进行人工污秽试验，利用泄漏电流测量系统记录其在运行电压作用下、不同相对湿度时的泄漏电流波形并对此进行分析；采用BP人工神经网络的方法，建立了不同湿度下的泄漏电流最大值之间的对应关系；选择Levenberg-Marquardt快速学习算法对建立的BP神经网络进行训练。利用部分试验数据进行的验证以及采用不同方法获得的泄漏电流随相对湿度变化曲线均表明，使用该神经网络来建立不同表面受潮状态时泄漏电流最大值之间的关系是准确有效的。     

饱和受潮绝缘子外绝缘状态评估系统的试验验证

污闪问题是电力系统最重要的问题之一。为了有效预防污闪,介绍了一套绝缘子外绝缘状态评估系统。该系统综合考虑绝缘子型号、线路电压等级、相对湿度、最大泄漏电流等因素的影响,对绝缘子的外绝缘状态尤其是闪络电压做出预判,进而防止污闪事故的发生。基于这套外绝缘状态评估系统,研究了等值附盐密度(equivalentsalt deposit density,ESDD)、绝缘子串长以及绝缘子表面污层饱和受潮时泄漏电流最大值与污闪电压的关系,并对同一ESDD下的实测污闪电压和估算污闪电压进行了对比。结果表明,当所选用的XWP2-160型绝缘子的串长分别为28、21、14片时,污闪电压的实测值和估算值的最大相对误差分别为4.6%、6.6%、5.5%。对比结果最终验证了该系统的可靠性和准确性。     

涂覆RTV对瓷绝缘子盐密和灰密影响的对比观测

绝缘子盐密和灰密值是污区分级和外绝缘配置的基础,各地污区分级观测绝缘子往往以XP-70瓷绝缘子为观测绝缘子,涂覆室温硫化硅橡胶(RTV)涂料对绝缘子积污特性的影响是一个值得关心的问题。因而选择深圳地区54处代表性的输电杆塔进行涂覆RTV与未涂覆RTV的XP-70绝缘子不带电挂样观测对比,测量了积污期为2a的绝缘子盐密、灰密和灰密盐密比,对比了涂覆RTV与未涂覆RTV线路绝缘子上表面、下表面与单片均值积污规律的差别。结果表明:涂覆RTV的绝缘子与未涂RTV的XP-70绝缘子相比,上表面盐密值增加约1倍,下表面盐密值、单片盐密均值增加约2倍,上表面灰密值增加约2倍,下表面灰密值、单片灰密均值增加约3倍,涂覆RTV的XP-70绝缘子灰密盐密比大于未涂覆RTV绝缘子的灰密盐密比。污秽外绝缘配置时在注意到涂覆RTV对绝缘子污闪电压大幅提高的同时,也应注意到涂覆RTV对绝缘子积污特性的影响。