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.     

计算高压直流输电线路等效干扰电流的一般性方法(英文)

As a critical part in the DC filter design,it is very important to quickly and correctly calculate the equivalent disturbing current.A general method for calculating the equivalent disturbing current of high voltage direct current(HVDC) transmission lines is proposed.In this approach,one 12-pulse converter was represented by four 3-pulse harmonic voltage sources in series,the DC network was described by a multi-phase coupled transmission line model,and the harmonic currents of certain frequency were solved based on the basic nodal analysis method.The multi-phase coupled transmission line model was described briefly,which could treat DC transmission lines of any structure,e.g.one or two DC circuits in a tower.The harmonic voltage source calculation steps were outlined,the steps to form the nodal admittance matrix were discussed,and the equations to calculate the equivalent disturbing current of the DC line were given.To verify the general applicability of the suggested approach,two different HVDC projects were studied:a traditional single circuit HVDC project,and a newly constructed HVDC project with double circuits on a same tower.The results show that the proposed method can calculate the equivalent disturbing current of the above two projects effectively,and has obvious advantages such as easy implementation,fast calculation and wide applicability.According to the two cases,the distributions of the equivalent disturbing currents along the line have the same trend,i.e.,the maximum value of the equivalent disturbing currents appears at the line inlet of both sides.Plus there is no fixed relationship between the equivalent disturbing currents and the HVDC line structures,because the equivalent disturbing current depends on many factors,such as background harmonics and converter transformer parameters.     

交直流复合电压下电晕放电实验研究(英文)

Converter transformers are one of the most important electrical apparatuses in the ultra high voltage(UHV) DC transmission systems.The valve side and the low voltage(LV) bushing are stressed by long-term AC and DC composite voltage leading to significant partial discharge(PD) and posing great danger to the insulation system.In this paper AC and DC composite voltage is applied on a metal needle-plate model to produce PD signal sequences,and then the pulse waveshape and frequency spectrum are analyzed and compared with PD signals under conventional AC or DC voltage.In the end,the phase-resolved distribution is analyzed to depict the new characteristics of PD under this composite voltage.     

特高压直流输电系统换流站的优化设计(英文)

Based on the consultation and study for Xiangjiaba-Shanghai ±800 kV UHVDC(ultra high voltage direct current) project,this paper presents an optimal design for key technique solutions.In this paper,the DC system electrical scheme design,the DC filter design,the DC harmonic component suppression,the over voltage and insulation coordination,the requirements for converter station equipment,the main equipment technical parameters of equipment(including thyristor valve,converter transformer,smoothing reactor,DC breaker),the configuration of measuring device and DC control protection system,and the de-icing operation design are investigated.According to the UHVDC technology researched conclusions and the development of the project construction,the UHVDC system design for converter stations becomes an optimal combination.The optimized design solves numbers of technical problems of the world’s first UHVDC project,and it is applied to the project’s construction.Under the actual operating condition,the optimized design is proved to be correct and superior.These optimal design conclusions are impartment for developing UHVDC technique and equipment,and provide reference for future UHVDC projects.     

特高压直流与双回超高压交流同塔架设输电线路导线布置方式及换位方式分析(英文)

For AC and DC hybrid transmission lines,the arrangement and transposition modes of AC conductors not only affect the unbalance factor of AC lines,but also influence the bias current of DC converter transformers by AC and DC coupling.Excessive bias current will influence the normal operation of converter transformers,thus the optimal AC phase arrangement and transposition mode of hybrid lines was studied to minimize the coupling effect between AC and DC lines to fit the requirements on both aspects.Based on the parameters of the Ximeng-Shanghai project in China,a detailed simulation model of the DC converter station and the hybrid transmission line with double-circuit AC 500 kV transmission lines and DC ±800 kV transmission lines were presented in the software PSCAD-EMTDC,and the coupling effects of the hybrid transmission lines were elucidated.The fundamental frequency components of DC poles with different operation conditions,arrangements of conductors and operation modes were analyzed,and the effective arrangement and transposition limiting the fundamental frequency current component of the DC line were compared.Simulation results show that AC operating conditions can affect DC induced components while the DC system operation mode has no apparent effect.With compact arrangement and inconsistent transposition of AC lines,the fundamental frequency component on DC lines can be reduced effectively;the three-transposed mode within the hybrid line is the optimal layout scheme,considering both the requirements of DC bias current and AC unbalance degree.     

±1100kV特高压直流输电系统换流变压器设计(英文)

Technical scheme of ±1 100 kV converter transformers is discussed in this paper.Important parameters such as impedance,capacity rating,and insulation level are introduced,and the possible design solution is discussed based on the transportation limitation,which is followed by a structure design and an integrating scheme discussion.The minimum impedance limit and natural impedance are checked considering the voltage fluctuation and the reactive power,and finally the impedance,24% for ±1 100 kV ultra high voltage direct current(UHVDC) projects,is obtained.Lightning impulse withstanding level(LIWL) and switching impulse withstanding level(SIWL) at the valve side of HY transformer is 2 300 kV and 2 100 kV respectively,about 28% and 31% higher than that of ± 800 kV projects.±1 100 kV converter transformers could be designed according to three solutions: conventional design,units in parallel,and components of transformers transported to site and assembled on site.A simple solution to integrate an UHVDC project into UHVAC systems is discussed according to the reduction of transporting transformers by railway.     

锦屏—苏南±800kV特高压直流输电工程交流滤波器优化设计(英文)

In DC transmission systems,AC filters can effectively reduce the hazards of harmonics,and compensate the reactive power requirements of the converters,thus the type and parameter choice of the filters is important.Therefore,based on the system conditions of Jinping-Sunan ±800 kV UHV DC(ultra-high voltage direct current) transmission project and the main harmonics,three types of filters were designed.The parameters of filter components were determined according to the reactive power compensation.By calculating the filter performance and rating,the results show that the parallel tuning with greatly over-currents appears in the low-voltage arm of BP11/13 filter.In order to avoid this kind of danger,a filter named BP11/BP13 is designed.Studies show that this type of filter can fully meet the filter performance requirements and avoid the over-current.It is concluded that the filter BP11/BP13 can reduce the rating of the components and enhance the stability in the long-term operation.     

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.     

基于故障树分析的电力变压器可靠性评估方法(英文)

Accurate assessment of system reliability with limited or insufficient statistical data is difficult. At present, to assess the reliability of the transformers primarily depend on the statistics data, and the result of the assessment does not accurately reflect the reliability of a transformer. Fault tree is a powerful tool for depicting the logical relationships between the faults system. However, for a sophisticated reliability system, like power transformer, fault analysis is hard or infeasible because of the complexities of the equipment configuration and its faults. This paper presents a method which overcomes the drawbacks of traditional fault-tree analysis (FTA) by using FTA based on fault probability and equivalent calculation of each failure mode. Based on the further analysis of typical failure modes and influences of power transformer, the fault-tree of transformer is set up by using FTA techniques and the assessment method for the reliability of transformer is put forward, combined with the index of the importance and the method of improved analytic hierarchy process(IAHP). The assessment examples show the method can deduct the failure modes of transformer clearly, meanwhile, find out the weaknesses in time during the operation and get better assessment results. The method is helpful for the reliability analysis of a sophisticated system.     

锦屏—苏南±800kV特高压直流输电工程直流滤波器的暂态额定计算(英文)

DC filter components and devices in converter stations of a high voltage DC transmission project may withstand a certain amount of transient overvoltage due to the impact of transient impulses.In order to protect them,suitable arresters should be equipped properly in the filters to limit the transient overvoltage to an acceptable level.By utilizing the method of DC filter simulation and transient calculation model,the paper studies the transient overvoltage in the DC filters of the Jinping-Sunan ultra high voltage direct current(UHVDC) transmission project under the most severe transient operation conditions.Three arresters are installed inside each filter,which consequently decide the insulation levels of the filter component: mainly capacitors,reactors and resistors.The lightning impulse insulation levels for the high voltage reactors of the two filters are 648 kV and 788 kV respectively,while they are 464 kV and 627 kV for the low voltage reactors,and 648 kV and 788 kV for the resistors.The insulation level for the high voltage capacitors is no more than 815 kV.The calculation results provide basis for choice of the DC filter components.     

染污方法对瓷绝缘子直流污闪特性的影响

在人工污秽试验中,IEC标准推荐了几种染污方法,但未给出不同方法试验结果差异的相关说明。为此,采用大吨位瓷绝缘子XZP-300为试品,研究了定量涂刷法、浸污法2种染污方法获得的瓷绝缘子试品在不同盐密条件下的直流污闪特性,比较了2种染污方法试验结果的概率分布特性,同时分析了2种试验方法试验结果的差异,并基于污闪平板模型从原理上解释了差异的原因。结果表明,定量涂刷法和浸污法的试验结果均近似呈正态分布,可以采用2种方法均值计算50%耐受电压;定量涂刷法获得的污闪电压高出浸污法的污闪电压约2%～6%;通过基于平板模型的公式推导可证明,均匀染污表面的污闪电压低于不均匀染污表面的,由于浸污法染污绝缘子表面盐密分布比定量涂刷法的更均匀,因此浸污法的污闪电压低于定量涂刷法的。     

污闪电压与等值盐密理论关系式的推导与应用

基于局部电弧—剩余污层串联模型及相关结果,利用假设条件和相关参数间的关系,导出了污闪电压与等值盐密及其它多个参数间的理论关系式,该式表明污闪电压与等值盐密是幂函数关系,其中系数 K受多个参数影响,而指数P只与电弧常数n 有关。应用该式表达和解释了若干实验结果,给出了通过 P计算n 的方法。该理论式可用于污闪问题的分析研究。     

概率统计在绝缘子污闪风险性评估中的应用

笔者分析了灰密的概率密度分布,并推导出盐密与灰密的联合概率密度函数。在不考虑灰密和考虑灰密两种情况下,利用概率统计方法,推导出在恒定电压下,绝缘子的污闪概率计算方法,为评估线路可靠性、调度部门决策、绝缘子的维护以及新线路绝缘子的选型提供依据。     

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。     

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。     

自然积污绝缘子的污闪电压和泄漏电流特性试验研究

以浙江电网自然积污FC70P/146、XWP2-7绝缘子为对象,对自然积污绝缘子的污闪电压和泄漏电流特性进行了试验研究;提出了考虑污秽折算系数的自然积污绝缘子外绝缘特性试验研究方法,采用数据拟合方法得到了自然积污绝缘子表面等值盐密、灰密及上下表面积污不均匀性对污闪电压及泄漏电流的影响规律。结果表明:对于自然积污FC70P/146和XWP2-7绝缘子,污闪电压的不均匀度影响特征系数N分别为0.128 5和0.095 9,要小于人工污闪电压的N值。对于FC70P/146绝缘子,泄漏电流的平均等值盐密影响特征指数a和不均匀度影响特征系数N分别为0.757 2和0.218 8;对于XWP2-7绝缘子,a和N分别为0.454 7和0.180 8。相对而言,FC70P/146绝缘子的a、N值要大于XWP2-7绝缘子。     

污秽绝缘子表面干区形成的影响因素

干区的形成是绝缘子污闪发生的一个必要条件,干区的形成受电压、污秽种类和含量、天气等诸多因素的影响,研究干区形成的影响因素问题,不仅有助于更加深刻地认识干区的形成,而且可以完善外绝缘污闪理论。为此,以矩形污秽玻璃片模拟实际绝缘子,在人工雾室中试验研究了污秽和雾对干区形成的影响。试验结果表明:随着等值附盐密度(ESDD)的增加,干区的形成时间逐渐缩短,干区宽度逐渐减小;随着等值附灰密度(NSDD)的增加,干区的形成时间逐渐变长,干区宽度逐渐增大;随着雾浓度的增大,干区的形成时间不变,干区宽度逐渐减小。此外,基于热量平衡理论对这些影响趋势给出了解释。研究结果表明ESDD、NSDD和雾浓度对于干区的形成是有影响的。     

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。     

基于微波辐射理论的绝缘子污秽等值盐密/灰密检测模型

用微波辐射计测量绝缘子污秽表面亮度温度,从而可获得污秽的辐射能量特性。提出用亮度温度计算绝缘子污秽等值附盐密度(equivalent salt deposit density,ESDD)、等值附灰密度(non-soluble deposit density,NSDD)的检测模型以及盐密和灰密乘积形式的检测模型。在不同测量角度下,研究干燥(相对湿度20%)和湿润(表面形成水膜)条件下,ESDD和NSDD与天线温度的关系,同时研究天线温度与环境温度及湿度的关系,并分析湿度对模型参数的影响。结果表明:ESDD和NSDD对天线温度的影响是独立的,通过测量天线温度可以同时测定ESDD和NSDD。     

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。