共查询到19条相似文献，搜索用时 265 毫秒
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当电动机发生各种不对称故障时,应用对称分量法,可将定子电流分解为正序、负序和零序分量。电动机在正常运行时负序和零序分量没有或很小,一旦出现,则表示电动机发生了故障。因此可利用负序和零序分量的有无来鉴别各类不对称故障。电动机的对称过载、短路等以过电流为特征的故障可通过检测电流幅值来检测其过流程度。这样以检测过流、负序和零序电流分量为基础的故障判据将具有很高的灵敏度和可靠性。1,关于过流、负序和零序电流的故障判据电动机的故障形式可分为对称和不对称两类。对称故障包括过载、堵转和三相短路等,这类故障对电动机的… 相似文献
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短路故障是电力系统运行中的一种常见故障,计算系统中发生短路故障时的电流和电压参数具有重要的意义。本文以对称分量法的正序、负序、零序分量为基础,合并正序、负序分量为相序分量,然后在中性点与地之间引入零序接地阻抗得出简化的等效电路。针对中性点有效接地和非有效接地的电力系统在三相对称短路的情况下,使用等效电路计算了两种情况下的电流及电压参数,并用PSCAD软件的仿真结果验证了计算结果的正确性。 相似文献
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本文从变压器短路后的分析入手,提出了几种检查和检测变压器绕组变形的方法,重点介绍了频率响应法测量变压器绕组变形的原理、具体判断方法、判断步骤及主要优点。最后通过短路电流与绕组变形的分析,提出了预防变压器绕组变形的几种有效措施。 相似文献
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在三相变压器一次侧加励磁电流,利用相量图可计算出变压器一、二次绕组电压的相位移组别.分别在变压器一次侧两相间加上50V的电压,再分别测出二次侧两相间的线电压,根据特征电压便可以判断出变压器的连接组别. 相似文献
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变压器在运行中,由于内部故障,有时候我们无法及时辨别和采取措施,容易引起一些事故,采取瓦斯继电器保护后,一定程度上避免了类似事件的发生。但是当变压器发生区外短路故障时,变压器受此短路电流冲击影响,本体不仅会产生振动,而且流经变压器的短路电流使变压器产生油流涌动,油流涌动会引起瓦斯继电器误动作。本文从云南电网公司500k V曲靖变电站在区外故障时进口瓦斯继电器误动作现象入手,寻找引起瓦斯保护误动作的原因,并提出提出芯式变压器瓦斯保护应采取的防误动措施。 相似文献
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魏万杰 《科技成果管理与研究》2008,(10):71-73
在大短路电流作用下,机械损伤的基本形式是变压器绕组变形,它们发展的典型方式是变形引起局部放电,匝、层间短路,整段主绝缘放电或完全击穿导致主绝缘破坏。因此,变压器出口短路后的检测试验一项必要的关系到运行安全的重要工作。 相似文献
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In this paper, a different internal fault modeling and an identification algorithm are presented. There has been an increasing concern about turn-to-turn faults in transformers because of the high costs of unexpected outages. It is not always possible to analyze the transformer behavior under such faults at rated conditions, since the tests are highly destructive. To develop transformer internal fault detection technique, a transformer model to simulate internal faults is required. This paper describes a novel technique and methodology for modeling and identifying transformer internal faults by using transmission line method (TLM) and fuzzy reasoning technique based on dynamic principal component analysis (PCA), respectively. The transformer has been modeled considering non-linearities as hysteresis and saturation. Transformer internal fault currents are successfully discriminated from the rated currents. The degree and priority of transformer internal faults are obtained by the proposed method. It is suited for implementation on computers because of no computation complexity. Hence, the proposed algorithm can be used effectively in real-time fault identification problems. 相似文献
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介绍了UPS中常用的辅助电源拓扑-反激电路。详细分析了反激电路工作原理,重点围绕着反激电路能量传递的核心-隔离变压器,进行讨论。详细介绍了变压器的设计方法,并进行了实践。 相似文献
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某厂1台变压器在定期油色谱分析试验中发现油中溶解气体成分含量异常,可能变压器内部存在潜伏性故障。停运后对变压器进行局放试验,试验结果异常。通过对局放试验前后的油色谱分析结果后,对变压器进行解体检查,发现故障是由静电屏短路及垫脚与箱底处导通引起的。通过更改静电屏结构和垫脚绝缘后,该变压器重新投入正常运行。 相似文献
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经典法是分析一阶线性电路暂态过程的一种常用的数学方法,要求按照电路定理列出微分方程,然后求解微分方程,计算过程比较繁琐;三要素法是对经典法求解一阶线性电路暂态过程的概括和总结,不必列出和求解电路的微分方程,直接计算出待求响应变量的初始值、稳态值和电路的时间常数即可,具有简捷方便的优点。目前供电工程教材中,采用经典法来求解无限大容量电力系统短路暂态过程的瞬时表达式,计算量较大,其中表达的物理含义不够明确。在实际的教学过程中,教学效果不够理想。采用三要素法来求此过程的瞬时表达式,旨在简化分析过程,帮助学生更好地理解该部分内容。 相似文献
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Myron Pawley 《Journal of The Franklin Institute》1933,215(2):133-147
A selective amplifier is developed which is simple, and more flexible than other types. It utilizes an audio transformer with a variable series resistance in the primary circuit, and a variable secondary load capacitance both of which may be adjusted to give broad or narrow peaked amplification at any frequency within a wide range, or flat amplification throughout this range. Theoretical and experimental amplification curves are shown, and a transient solution gives the primary and secondary currents resulting when a voltage is suddenly applied to the amplifier. This analysis shows that the time constants for the circuit are comparable with those for other peaked amplifiers. Oscillograms are shown illustrating the transient behavior of the amplifier. 相似文献
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G.P. Chhalotra 《Journal of The Franklin Institute》1976,302(1):85-103
A mathematical analysis of sequential fault transients due to series and shunt faults is important in the study of circuit breaker pole openings and reclosings with arc resistances. The line loading itself becomes unbalanced momentarily due to load switching. Each double fault is developed in sequence, therefore the initial currents in the second and third fault must be treated properly under transient conditions. New sequence component variables λμ0 and ρσ0 are used with αβ0 components. This study is useful for small power systems as well for large power systems. A digital simulation of various series and shunt faults is presented in a generalized manner using αβ0, λμ0 and ρσ0 components. 相似文献
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300Mw及以上机组通常接成发变组单元接线,并通过变压器高压侧断路器与系统相连。机组正常运行时,由于种种原因,使断路器自动跳闸,运行人员应正确判断并及时处理,以保证机组安全运行。 相似文献