共查询到20条相似文献,搜索用时 46 毫秒
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基于小波多分辨率分析理论,提出了一种以能量变化率的比值作为判据,区分变压器励磁涌流和内部短路电流的新方法—小波能量谱图解法。它从信号的小波能量谱图中提取特征量,作为模式识别的依据来鉴别励磁涌流和内部短路电流。仿真计算表明该方法简单有效,具有一定的应用前景。 相似文献
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当前的励磁涌流识别方法误差偏大,难以区分电力故障类别.为此,提出基于小波变换的励磁涌流识别方法.引入小波变换方法,结合塔式算法,完成电力离散信号的分解.通过小波重构滤波器,重构电力离散分解信号.针对励磁涌流识别中故障类别判断难的问题,利用小波能量谱图解法来区分电力系统变压器励磁涌流故障和内部短路电流,完成励磁涌流识别的优化.实验结果表明,研究方法的励磁涌流识别结果与真实情况一致,具有较好的识别准确率。 相似文献
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小波变换在励磁涌流和短路电流识别中的应用 总被引:1,自引:1,他引:0
为了识别励磁涌流电流和内部故障电流,根据小波变换后励磁涌流在高频率段处呈现出明显的奇异性的特点,利用小波变换对变压器的励磁涌流模型和内部故障模型进行仿真分析,确定了基于一尺度下奇异值的小波判据,比较其高频段上能量的变化情况来识别励磁涌流和内部故障电流。结果表明,此方法可以对励磁涌流和内部故障电流进行良好识别。 相似文献
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基于小波包和LS-SVM的变压器励磁涌流与短路电流识别方法 总被引:1,自引:1,他引:0
基于小波包分解和最小二乘-支持向量机(LS-SVM),提出了变压器短路电流和励磁涌流识别的新方法。通过将电流信号进行小波包分解,计算出分解后各频段信号的能量,组成能量特征向量,并考虑作为最小二乘一支持向量机分类器的输入参数,来实现短路电流和励磁涌流的识别。仿真结果表明,该方法识别准确率高,受噪声的影响小。 相似文献
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针对变压器采用纵差动保护会受到励磁涌流的影响而误动作,以及励磁涌流和内部故障时的短路电流的区分问题,提出一种根据变压器两侧三相瞬时功率因数的变化关系来识别励磁涌流和内部故障的方法.该方法简单、便捷,从能量的角度进一步揭示了变压器励磁涌流与内部故障电流本质不同. 相似文献
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Current transformers (CTs) provide instrument-level current signals to meters and protective relays. Protective relays' accuracy and performance are directly related to steady-state and transient performance of CTs. CT saturation could lead to protective relay maloperation or even prevent tripping. This paper proposes the use of an artificial neural networks scheme to correct CT secondary waveform distortions. The proposed module uses samples of current signals to achieve the inverse transfer function of CT. Simulation studies are preformed and the influence of changing different parameters is studied. Performance studies results show that the proposed algorithm is accurate and reliable. The proposed algorithm has also been implemented and tested on a digital signal processor board. Details of the implementation and experimental studies are provided in this paper. 相似文献
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Tatsuo Kawamura Eiichi Haginomori Yutaka Goda Tetsuya Nakamoto 《IEEJ Transactions on Electrical and Electronic Engineering》2007,2(5):516-522
The Short‐circuit Testing Liaison (STL) is the organization that consists of high power testing laboratories of the world. Member laboratories perform short‐circuit tests under uniform interpretations of the IEC standards agreed through technical discussions and information exchanges among them. One of the recent projects that the STL has been working on is to establish uncertainty and traceability of high current measurement by international comparison tests with reference shunts. In concert with this project, the IEC Working Group is preparing the new standard for high current measurements. Copyright © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. 相似文献
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A mathematical model of the commutation process that occurs in a dc machine that uses rolling contacts is presented. Some results of investigations of the representing model are shown. The functionality of such machines is demonstrated. 相似文献
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Anndkkage U.D. Ming Yu Mclaren P.G. Dirks E. Parker A.D. 《Power Delivery, IEEE Transactions on》2000,15(2):515-519
Differential protection schemes for busbars, generators or transformers connect multiple current transformers in parallel across a common burden. This paper describes the techniques used to simulate such an arrangement and concentrates particularly on the three current transformer case 相似文献
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针对高压内置变压器空投导致零序电流保护误动的问题,从系统层面研究计及涌流影响的零序电流保护风险评估,以完善现有风险评估模型在涌流场景下未涉及盲区的不足。考虑影响涌流产生的多因素并非完全可得,提出了一种计及参量完备性的误动概率计算模型。在参量信息缺失不可得时,利用电网设备状态监测数据库中的数据补充计算,并分配相应的权重得到综合加权误动概率。在此基础上给出了具体风险指标和操作建议。通过具体的算例对所提出的风险评估方法进行展示,评估结果与实际运行中线路和母联动作结果一致。 相似文献
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The design and principle of action of the new multiband transformer of a current is considered in which the expansion of the top range of measurements is carried out by creation against a magnet driving force in the closed core. 相似文献
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H. Takayanagi H. Nakano K. Yonemoto K. Horio 《Journal of Computational Electronics》2006,5(2-3):223-227
Two-dimensional transient simulations of GaN MESFETs are performed in which a three-level compensation model is adopted for
a semi-insulating buffer layer, where a shallow donor, a deep donor and a deep acceptor are considered. When the drain voltage
V
D is raised abruptly (while keeping the gate voltage V
G constant), the drain current I
D overshoots the steady-state value, and when V
D is lowered abruptly, I
D remains a low value for some periods, showing drain-lag behavior. These are explained by the deep donor’s electron capturing
and electron emission processes. We also calculate a case when both V
D and V
G are changed abruptly from an off point, and quasi-pulsed I-V curves are derived from the transient characteristics. It is shown that the drain currents in the pulsed I-V curves are rather lower than those in the steady state, indicating that so-called current collapse could occur due to deep
levels in the semi-insulating buffer layer. It is also shown that the current collapse is more pronounced when V
D is lowered from a higher voltage during turn-on, because the trapping effects become more significant. 相似文献