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电网运行的实际情况表明 ,变压器保护的安全性与可靠性至关重要。文中以近期的两次事故为例 ,分析了河北南网变压器保护运行中存在的若干问题 ,并针对这些问题提出了整改措施。文章认为 ,现存问题的彻底解决 ,不仅应从保护的配置、选型、运行方式、定值计算等几方面着手进行 ,还需从直流系统的配置与改造、TA的布置、系统运行方式等方面共同采取措施。 相似文献
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电网运行的实际情况表明,变压器保护的安全性与可靠性至关重要.文中以近期的两次事故为例,分析了河北南网变压器保护运行中存在的若干问题,并针对这些问题提出了整改措施.文章认为,现存问题的彻底解决,不仅应从保护的配置、选型、运行方式、定值计算等几方面着手进行,还需从直流系统的配置与改造、TA的布置、系统运行方式等方面共同采取措施. 相似文献
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地区电网孤网运行时的频率控制是维持系统稳定的重要方面,当孤网系统转动惯量小,仅依靠高周切机、低频减载等措施可能无法满足系统频率要求,还会造成火电机组OPC保护频繁动作,系统频率振荡。针对新疆石河子电网孤网后的高频问题,通过OPC各项参数的深化研究(包括OPC保护动作频率值、动作时延、关闭时间间隔以及高压阀门关闭与否等参数)、不同机组间OPC协调配合研究以及OPC与高频切机协调配合研究等,提出一整套OPC保护定值配置原则,以避免或减少孤网运行时的系统频率振荡。 相似文献
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介绍了地区电网发生的一起故障:由于运行方式的特殊性导致了继电保护的相继动作,引起了大范围的停电。针对这类现象从运行方式和保护配置方面提出了改进措施,以避免事故的再次发生。 相似文献
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本文分析了国内地区电网以220 kV环网运行为主网架的情况下,220 kV电网继电保护整定的基本原则及存在的矛盾,以及元件保护误动和拒动时对电网的不同影响,进一步说明了220 kV系统元件保护双套配置的必要性,同时提出不同电网设备在双配置继电保护情况下,双套继电保护装置运行方式的安排面临的问题及对策,从而在继电保护防误动和防拒动方面取得最优化,使得继电保护装置发挥最好的效果。 相似文献
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《电气》2011,(2):14-18
With the incessant development of power market reform,the existing cross-subsidy in electricity tariffs has become a critical problem in China’s power industry development.On the basis of the theories of cross-subsidy and electricity universal service,the authors take foreign countries’ experience as reference to design several solutions to cross-subsidies in electricity tariffs in different phases of China’s power industry development.Furthermore,the application and implementation of these solutions are analyzed in this paper. 相似文献
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The author suggests that the confidence which many biologists have in problem-solving methods is unwarranted and that there are very important limitations in almost all current methods for solving biological problems. The standard problem solving approach that computer scientists use is outlined. An example of an error in an evolutionary tree problem-the case of the African Eve-is discussed 相似文献
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无色透明材料形成的单层薄膜,其颜色由干涉色决定。以白光照射其表面,随薄膜厚度的增加,将出现一系列色彩,这是由薄膜干涉所致。我们可以根据薄膜颜色,估计薄膜厚度。显然,当厚度增大到后界面的影响可以忽略不计的程度(相当于只有一个界面的半无限大情形,本文简称“厚膜”),则“厚膜”颜色恢复为无色透明。半透明材料在基底上形成的薄膜系统,以白光照射所呈现的颜色,由于基底及吸收的影响,则不能简单地以薄膜干涉来分析。对于半透明薄膜系统,首先测量它的光强反射率谱和透射率谱,运用传递矩阵[1]方法计算出薄膜的介质光学常数,再以光学常数计算单层薄膜与“厚膜”的光强透射率谱与反射率谱及它们的色坐标。以菲涅耳公式计算出的反射率谱为半无限大介质反射率谱,这时的色坐标可视为“厚膜”的色坐标。 相似文献
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A survey is provided of Japanese research on ceramic materials for substrates, microwave dielectric ceramics, piezoelectric ceramics, semiconducting ceramics, and superconducting ceramics. Novel processing technologies are described, covering the use of amorphous materials, superfine powders, lamination, multilayer thin films, porous ceramics, and superlattices 相似文献
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Recent progress in inverse problems in electrocardiology 总被引:5,自引:0,他引:5
The considerable progress achieved in the inverse problem of electrocardiography over the last decade has provided grounds for optimism about the possibility of approaching significant clinically relevant applications in the next decade. However, there are a number of basic questions that still remain. In addressing these questions, the authors feel it is important to seek solutions that emphasize physiological rather than mathematical significance. This approach leads to twin requirements for useful inverse solutions: accuracy, defined in a physiologically meaningful (and not just averaged and mathematical) sense, and reliability, not only to measurement noise but also to geometric modeling errors and other uncertainties that are inescapable in practical application. Studies using analytically tractable models may still be relevant, but it seems more important to find solutions to practical inverse problems, which will move the field toward wider acceptance and credibility 相似文献
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