电流互感器一次通电中异常情况的原因分析

电力系统中对电流互感器（下文简称CT）二次回路接线的正确性及完整性判断,是通过对CT进行模拟通电试验来进行的。介绍了在一次检查CT回路接线是否正确的一次通电试验中所遇到的异常情况,并对其进行了分析,指出在对CT进行通电试验时,应该采用一次通电方式,并且要在CT一次接线完善的情况下进行,以防止由于CT一次问题导致的CT回路异常情况的发生。     

电流互感器一次通电中异常情况的原因解析

在电力系统当中,对电流互感器,也就是CT的二次回路的接线的正确性和完整性的判断,主要是通过对CT进行模拟通电的试验来进行的,本文就介绍了在一次检查CT的回路接线是否是正确的一次通电试验当中所遇到的异常的情况,并对其进行了简要的分析。     

一种变压器短路试验CT二次回路自动校验装置及系统

介绍了一种变电站变压器短路试验CT二次回路自动校验装置及系统,用于验证变压器各侧CT绕组二次接线的正确性。通过简易的试验接线即可开展变压器短路试验,再将短路试验测试数据输入CT二次回路校验系统,即可自动完成CT二次回路正确性校验。     

继电保护改造工作的主要风险点及注意事项

阐述了某发电厂继电保护改造工程中拆线工作、CT/PT回路接线工作、CT/PT回路通电工作、一次设备传动工作、交流回路相量测试工作存在的主要风险点,并提出了针对性的防范措施和应注意的问题。     

两组直流串电引起的一起操作回路异常分析

对一起直流串电引起的操作回路异常情况进行了检查分析,根据故障出现的现象,采用排除法,最终查出二次接线错误为异常现象出现的原因.改正接线,并提出一种判断直流系统接线正确与否的检查方法.     

变压器、电抗器的一次通流试验

在工程试验中,对于高阻抗设备（变压器、电抗器）的电流回路的差动试验主要是以极性试验为主。本文阐述一种从一次接线端给变压器、电抗器通流,检查CT二次接线的极性、变比试验以及差动回路的正确性。     

500 kV鹏城变电站技改中CT回路危险点分析及防范

为配合500 kV鹏城变电站一次设备的更换,二次回路需要执行必要的安全措施.针对二分之三接线方式下一次设备更换过程中和一次设备更换后二次回路的验收中CT回路可能存在的危险点,以及改造后送电过程中CT回路可能发生的危险点,进行了详细的阐述,并给出了相应的防范措施,确保二次回路安全措施的执行全面到位,对二分之三接线方式下二次回路的运行维护具有一定的指导意义.     

变电站二次回路运行异常及故障处理技术分析

二次回路是变电站二次设备的重要组成部分,正确、可靠的二次回路,有利于保障变电站二次设备安全可靠运行。变电站二次回路系统具有接线复杂、点多面广、运行环境差等特点,因此极易出现各种故障,如二次回路运行异常、接线异常等,及时发现并检查异常情况,有助于采取有效方法准确无误的排除故障。本文主要分析了变电站二次回路运行常见异常情况,有针对性地探讨了变电站二次回路运行故障处理措施,以确保变电站二次回路安全可靠运行。     

两组直流串电引起的一起操作回路异常分析

对一起直流串电引起的操作回路异常情况进行了检查分析,根据故障出现的现象,采用排除法,最终查出二次接线错误为异常现象出现的原因。改正接线,并提出一种判断直流系统接线正确与否的检查方法。     

电流互感器二次改接线引起变压器差动跳闸分析

正电流互感器(CT)是电力系统中继电保护、测量仪表、录波监视等二次设备获取电气一次设备回路电流信息的传感器[1]。因此,CT二次回路接线的正确性对于变电站而言至关重要。主变差动保护中的CT二次回路接线较复杂,二次接线出错概率较高。一旦CT二次回路接线出错,就会影响主变差动保护的正确动作,进而威胁到变压器的运行。在电网运行中,由于CT二次回路接线错误导致主变差动跳闸的现象时有发生。     

Correction of saturated current transformers secondary current using ANNs

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.     

Recent developments on high current measurement using current shunt

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.     

Commutation in the direct current machines with rolling current collecting

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.     

330 kV电流互感器电流异常故障分析

电流互感器是330 kV超高压电网中最重要的测量设备之一,其将系统中的大电流变换为仪表可直接测量的小电流,用于电能计量和保护控制.电流异常是较为常见的电流互感器故障,通过电流互感器的结构剖析分析了可能引起电流异常的原因,研究了因绝缘中出现分流通路导致二次电流偏小的机理.介绍了一起电流互感器电流异常故障的发现、检查和试验过程,研究了环氧浇注质量不良导致故障的原因,并最后提出了类似故障的防范措施和质量改进建议.     

Simulation of a differential current protection scheme involvingmultiple current transformers

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     

计及涌流影响的零序电流保护风险评估

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。     

Multiband current transformers

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.     

Simulation of slow current transients and current collapse in GaN FETs

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.