安徽电网2009年火电厂“锅炉四管”泄漏情况及分析

统计了安徽电网受监火力发电机组2009年度锅炉四管泄漏情况,分别按泄漏部位、泄漏原因、泄漏机组容量对锅炉四管泄漏进行了分析、总结。并就当前已经或可能出现的泄漏情况及四管泄漏防治措施进行了阐述。     

安徽省电力系统2008年度火力发电厂“锅炉四管”泄漏情况及分析

本文统计了安徽省火力发电机组2008年“锅炉四管”泄漏情况,分别按泄漏部位、泄漏原因、泄漏机组容量对“锅炉四管”泄漏进行了分析、总结。并就当前已经或可能出现的泄漏情况及“四管”泄漏防治措施进行了阐述。     

污秽复合绝缘子泄漏电流波形频谱特征

为了解复合绝缘子在污闪过程中泄漏电流变化特征,在人工雾室中开展了复合绝缘子污闪试验研究,测量和分析了试验过程中泄漏电流波形的时域和频域特征。分析结果表明,泄漏电流幅值、基波、三次谐波和五次谐波相互间具有较强的相关性,提出以泄漏电流最大值(Im)、总谐波失真率(THD)、泄漏电流基波相位差(θ)表征泄漏电流频谱特征;临闪时,泄漏电流具有幅值高、谐波含量少、泄漏电流基波与电压间相位差小的特点。研究结果为建立基于泄漏电流特征量的污闪预警系统提供了依据。     

污秽绝缘子高频泄漏电流特征的研究

泄漏电流和污闪放电的发展过程密切相关,监测泄漏电流是评估绝缘污秽状态的重要手段。为克服传统泄漏电流法的缺点,笔者通过人工污秽试验方法,研究了玻璃绝缘子的高频泄漏电流,并对几种污秽表面状态的高频泄漏电流的幅值、波形和频谱特征进行了分析,提出了污秽绝缘子的高频泄漏电流特征,以及高频泄漏电流特征参数与等值盐密的相关性。     

污秽绝缘子泄漏电流特性研究

为提高泄漏电流评估绝缘子污秽度的可靠性,综述了污秽绝缘子泄漏电流特性问题20余年的研究成果,其内容包括临闪前泄漏电流和污闪电压的关系;在运行电压下及绝缘子表面污层饱和受潮时泄漏电流和放电现象间的关系;泄漏电流和等值附盐密度(ESDD)、绝缘子形状、片数、污秽状况以及污闪电压的关系;以及在绝缘子表面污层未达到饱和受潮条件时泄漏电流和雾浓度、相对湿度、ESDD间关系的研究。基于泄漏电流与其他污秽度参数之间关系的研究开发出在实验室及变电站测量多参量泄漏电流的仪器,并在现场测量了大量泄漏电流及气象条件的数据。根据研究成果提出了利用运行电压下的泄漏电流最大值进行污闪预警的方法。     

某电厂1025t/h锅炉水冷璧泄漏原因分析

某火电厂锅炉水冷壁发生泄漏并导致机组停机.采用宏观检查、渗透检测、化学成分分析、力学性能检测、显微组织分析并结合检修、运行情况对泄漏原因进行了综合分析判断.结果表明:发生泄漏的主要原因为鳍片焊接不规范,鳍片焊缝发生开裂,裂纹扩展至水冷壁对接焊缝并裂穿导致介质泄漏.针对泄漏原因,提出了更换泄漏管段、扩大防磨防爆检查范围、...     

CFB锅炉省煤器吊挂管泄漏原因分析

某火电厂745 t/h循环流化床锅炉省煤器发生泄漏导致机组停机.采用宏观检查、壁厚检测、化学成分分析、力学性能检测、显微组织分析并结合运行、检修情况对泄漏原因进行了综合分析判断.结果表明:飞灰磨损是造成本次省煤器泄漏的最主要原因,泄漏介质的吹损造成邻近省煤器吊挂管及包墙过热器泄漏,机组最终停机.针对泄漏原因,提出了更换...     

火电厂高压加热器泄漏原因分析及对策

分析了高压加热器泄漏原因,认为主要为U形管本身泄漏以及管口与管板胀接、焊接等处存在缺陷所致。针对不同泄漏,提出了相应的处理对策,减少了高压加热器泄漏故障。     

绝缘子饱和受潮条件下泄漏电流预测方法

为通过测量绝缘子表面泄漏电流实现污秽程度的在线监测与预警,对影响绝缘子饱和受潮条件下泄漏电流的因素进行了研究。提出了一种在大空间试验室中控制环境湿度的方法,通过人工污秽试验研究了在不同湿度条件下充分受潮后的绝缘子表面污层泄漏电流,分析了等值盐密、环境湿度对泄漏电流变化趋势的影响,并探讨了绝缘子在不同湿度条件下的泄漏电流之间的关系。研究结果表明泄漏电流与绝缘子受潮过程密切相关,无温差条件下可近似认为低湿度条件下测得的泄漏电流与饱和受潮状态下泄漏电流满足线性折算关系。进一步给出了利用低湿度条件下泄漏电流预测饱和受潮条件下泄漏电流的方法,并讨论了其适用范围。     

基于灰关联算法分析环境因素对高海拔±800kV线路绝缘子泄漏电流的影响

为分析环境因素对±800kV直流绝缘子泄漏电流的影响,在特高压直流带电考核场对±800kV全尺寸线路绝缘子进行了长期带电考核。统计了3种材质(瓷、复合、玻璃)±800kV线路绝缘子在自然积污条件下的泄漏电流,利用灰关联算法计算了环境因素(环境湿度、温度、温度变化率)与绝缘子泄漏电流间的关联度,找出了影响泄漏电流的主要因素。分析结果表明:影响特高压直流绝缘子泄漏电流的环境因素主要为环境湿度,其中叶面湿度与泄漏电流关联度最大;温度变化率对泄漏电流的影响比温度大;不同时间段内泄漏电流与环境因素的关联度类似。     

矿用馈电开关漏电保护动作值的合理整定

在煤矿井下供电系统采用选择性漏电保护时,馈电开关通常会出现漏电动作值变动很多,尤其用作分支开关时大多出现漏电动作值变大或变小,有些开关漏电动作值已变得小于国家标准和行业标准,存在着安全隐患,主要分析导致漏电动作值变小或大的主要原因,以及如何在煤矿井下重新合理整定带选择性漏电保护的真空馈电开关.     

国内外空气预热器漏风试验规程的比较

空气预热器是利用锅炉尾部烟气的热量来加热燃料燃烧所需空气,以提高锅炉效率的热交换装置。目前．大容量机组多采用再生回转式空气预热器,体积小,重量轻,便于布置,但是,漏风较大,严重影响机组出力,这样,评定空气预热器的漏风情况便十分重要,为此,分析了国内和国外的漏风试验规程并比较两者之间的差异,对日常选择计算漏风率有参考价值。     

Leakage flux saturation effects on the transient performance of wound-rotor induction motors

The prediction of induction machine performance has traditionally been based on the constant parameter models. This approach was later replaced by considering saturation in the main flux paths. However, such models have not been sufficiently accurate for certain transient conditions such as on-line starting and short-circuit. So, an accurate study of their performance should necessarily consider the magnetic saturation effect both in the main and leakage flux paths. In this paper, an experimental procedure to determine the machine parameters and saturation characteristics is adopted. The adopted experimental procedure facilitates the measurement of both stator and rotor leakage reactance saturation characteristics. Two models of saturated induction motors are developed to predict the transient performance of a laboratory wound-rotor induction motor. The results calculated by the proposed models considering and ignoring the leakage flux saturation are compared with the experimental results. The model that considers saturation in the leakage flux paths produces more accurate transient responses.     

三分仓回转式空气预热器轴向和周向泄漏耦合计算

回转式空气预热器的周向泄漏和轴向泄漏气流彼此关联,相互影响,形成一个复杂的流体网络,文中给出了确定流动网络中周向泄漏和轴向泄漏气流方向和流量的方法。计算模型由节流孔流动方程和周向泄漏腔室混合过程质量能量守恒方程组成。以一台三分仓回转式空气预热器为例,对所有可能的泄漏方向进行了计算,在给定的主气流边界参数下,泄漏方向有唯一合理的物理解;不同密封间隙下的计算表明,正常状态下,烟气和二次风的周向泄漏方向与主气流流向一致,由于一次风压力最大,它从冷热两端同时漏入周向泄漏腔室;当轴向密封间隙达到周向密封间隙的3倍时,烟气周向流动方向发生变化,烟气周向泄漏腔室的气体从冷热两端同时泄漏到预热器进出口烟气气流中。     

Using deep learning to combine static and dynamic power analyses of cryptographic circuits

Side-channel attacks have shown to be efficient tools in breaking cryptographic hardware. Many conventional algorithms have been proposed to perform side-channel attacks exploiting the dynamic power leakage. In recent years, with the development of processing technology, static power has emerged as a new potential source for side-channel leakage. Both types of power leakage have their advantages and disadvantages. In this work, we propose to use the deep neural network technique to combine the benefits of both static and dynamic power. This approach replaces the classifier in template attacks with our proposed long short-term memory network schemes. Hence, instead of deriving a specific probability density model for one particular type of power leakage, we gain the ability of combining different leakage sources using a structural algorithm. In this paper, we propose three schemes to combine the static and dynamic power leakage. The performance of these schemes is compared using simulated test circuits designed with a 45-nm library.     

复合绝缘子接地电流的测量及其特性研究

目前检测复合绝缘子污秽状况的主要方法是泄漏电流法。这种方法需要在绝缘子上加装电流传感器,加大了测量难度和危险性。文章提出了通过测量绝缘子接地电流来检测复合绝缘子表面污秽程度的方法.对复合绝缘子的接地电流特性进行了研究,分别建立了复合绝缘子接地电流、体泄漏电流和表面泄漏电流的测试回路,对洁净和污秽条件下复合绝缘子上述3种电流进行了测量和比较分析。试验结果表明：污秽条件下复合绝缘子接地电流及表面泄漏电流的幅值比洁净条件下的都有明显增大,而且增大的幅度基本相同,而波形上谐波成分大大减小,但体泄漏电流基本没有变化。因此,通过测量复合绝缘子接地线上的接地电流可以用于检测出复合绝缘子的污秽程度。     

Diagnostic methods in revealing internal moisture in polymer housed metal oxide surge arresters

Diagnostic measurements performed for surge arresters are normally studied by evaluating their suitability to detect aging and degradation of metal oxide material. The suitability of different methods for revealing internal moisture in arresters has not been studied much. This aspect is considered in the paper based on measurement results obtained during a 1.5-yr laboratory test series conducted for six different types of polymer-housed distribution class arresters. AC power losses, third-harmonic content of resistive leakage current, DC leakage current, and partial discharge measurement results over the test period are given and discussed. Details of the measurement procedures suitable for measuring polymeric arresters with internal moisture are also studied. AC power loss and DC leakage current measurements were found to be good methods, whereas the other two can only be used as additional methods when diagnosing internal moisture in polymer-housed arresters.     

Excitation magnetic flux losses in acyclic motors with transverse magnetization

A theoretical analysis of the distribution of magnetic excitation flux components caused by permanent magnets in acyclic torquer motors with transverse flux magnetization is presented in the article. Magnetic leakage fluxes were assessed by formulas obtained for the computation of said fluxes. Assessments of their impact and recommendations to reduce leakage fluxes in acyclic motors are also given     

Frequency characteristics of leakage current waveforms of anartificially polluted suspension insulator

In order to establish a method for monitoring contamination in insulators based on leakage current waveforms and their frequency characteristics, the leakage current waveforms and frequency characteristics of an artificially polluted 180 mm diameter cap and pin type insulator were investigated by the wet contaminant and the clean fog methods at fixed applied voltages. As a result it was found that leakage current waveforms become similar to the symmetrical wave when strong local arcs occur; hence, the intensity of the odd order of harmonic components, e.g. 50, 150, and 250 Hz, is high. Furthermore, it was clarified that the transition of the leakage current waveforms, until flashover occurs, is classified into six stages and that a threshold exists by which the occurrence of flashover can be predicted     

抗冲刷截止阀密封结构的研制

阐述了电站锅炉的排污系统和疏水系统中的关断阀,造成阀门内漏的原因主要是冲刷和压伤.通过对截止阀密封结构的重新优化设计,研制出双密封面结构的截止阀,解决了阀门内漏的问题.