电流互感器错误接线分析

从电能计量的实际工作经验出发，探讨和分析了几种容易将CT极性反接导致计算装置错误接线的情况，并提出了完善的改正措施。     

电流互感器变比及接线错误造成计量误差

在用电检查中,发现某用户处更换电流互感器时电流比不配套,且接线又有错误,造成计量误差。面对这样大量漏计电量,感到追收电量很棘手,甚至影响用电分类。1 计量方式3相4线有功电能表为计量总表,该表负荷侧还装有一块单相电能表计量照明用电,两表相减的差值为生产电力用电量,依此收取分类电费。     

高压电能计量装置错误接线实例分析

介绍了高压电能计量装置错误接线造成的电能表计量误差,绘制了错误接线向量图,计算出错误接线更正系数,纠正了错误接线电量误差。对用户用电信息负荷异常曲线进行分析,判断高压电能计量装置故障,并给出了应用实例和结论。     

电能计量装置错误接线判断的方法及步骤

介绍了对现场中运行的电能表因错误接线带来的计量误差;对电能表错误接线的分析方法和步骤以及电能表因错误接线产生的差错电量的计算方法.     

电流互感器极性接反造成计量错误浅析

针对电能计量表由于互感器极性接反会出现计量错误的问题,具体分析了三相二元件电能表A相或C相电流互感器极性接反时所测量的功率情况,并指出要定期进行计量表计的接线检查,以保证计量的正确性。     

电度表错误接线的分析及改正方法

通过对有功电度表错误接线的理论分析，总结出更正错误接线的方法，经电能计量模拟接线装置检验表明该方法有效。     

并联变压器经济运行方式分析

阐述了基于变压器临界功率计算的变压器经济运行方式分析的基本原理,重点对双绕组和三绕组变压器的有功功率损耗进行了分析,对不同运行方式下变压器的有功功率损耗进行了比较。     

A semiconductor H-bridge connection to avoid saturation in current transformers for differential protection

Current transformer saturation can be the cause of misoperation or false tripping in power transformer differential relays during connection transients. To avoid this scenario, the authors propose a solution based on a current transformer flux controller system (CT-FCS). The CT-FCS consists of a controlled semiconductor H-bridge connected to the primary winding of current transformers, allowing the inversion of the currents polarity. Unipolar pulses with high content of DC current are converted into bipolar pulses that reduce or cancel the amount of DC component in current transformer cores. By canceling the DC component, a saturation-free operation can be obtained. The use of this method will allow the selection of current transformers with lower saturation factors and will reduce the size of such devices.     

Flow electrification in transformers: relevance of ECT and leakage current measurements

The accumulated charge Q on a well insulated pressboard part being probably the most relevant parameter for flow electrification evolution inside transformers but clearly not measurable in situ, we compare in this paper this parameter with others possible to measure. The two most commonly used are oil parameters: ECT (electrostatic charging tendency) and, to a smaller extent, the continuous aging test for tan /spl delta/. Another is not so often used because of measurements difficulties, but was considered to be one of the most relevant: the leakage current. Thus in this paper we compare on two facilities (specially made for that) the accumulated charge Q to the ECT and leakage current. We find that, even if sometimes a correct correlation exists between these parameters, several cases show a bad correlation. Thus monitoring transformers by analyzing only ECT or leakage current seems to be hazardous.     

Geomagnetically induced current effects on transformers

Geomagnetically induced currents (GICs) can cause saturation of the magnetic circuit of transformers in a power system. This saturation can increase the MVAr absorption of the transformers, leading to voltage-control problems, generating significant harmonic currents, and cause heating of the internal components of the transformer itself, leading to gas relay alarm/operation as well as possible damage. This paper sets out the methods used to examine these effects using a mathematical model explicitly incorporating the electric and magnetic circuits, including the shunting effect of the tank to predict the current and flux waveforms. The model has been used to predict GIC effects for a variety of winding connections for single-, three-, and five-limb core-type transformers connected to the National Grid Company plc transmission system in England and Wales. The size and form of the return limbs along with the tank shunting effect determine the magnitude and the often complex shape of the waveforms resulting from GIC. Field and factory DC injection tests on various types of transformers have been conducted to validate the model and gain an insight into the magnetic behavior of transformers. With the aid of finite-element analysis (FEA) techniques and a consideration of the various constructional arrangements of the core and coils in the tank, it is possible to evaluate the power losses and accompanying temperature rises of the core, structural components, windings, and tank. Some guidance on the acceptable GIC current levels for various transformer types is given.     

电子式电流互感器研究评述

对Rogowski线圈电流互感器和光学电流互感器这两种主要的电子式电流互感器进行了基本的评述.在动态测量品质方面,光学电流互感器优于Rogowski线圈电流互感器.两种电子式电流互感器都形成了实用化技术.电子式电流互感器对提高电网动态观测的准确性,对提高继电保护的动作可靠性,对于数字电力系统的建设都具有重要意义.     

电子式电流互感器研究评述

对Rogowski线圈电流互感器和光学电流互感器这两种主要的电子式电流互感器进行了基本的评述。在动态测量品质方面,光学电流互感器优于Rogowski线圈电流互感器。两种电子式电流互感器都形成了实用化技术。电子式电流互感器对提高电网动态观测的准确性,对提高继电保护的动作可靠性,对于数字电力系统的建设都具有重要意义。     

两变电站中变压器零序电流保护的分析

分析了栖变、姜变中变压器零序过流方向保护及零序过流保护的动作原理 ,阐述了其中的异同点 ,指出了姜变变压器零序过流保护的优越性。     

两变电站中变压器零序电流保护的分析

分析了栖变、姜变中变压器零序过流方向保护及零序过流保护的动作原理,阐述了其中的异同点,指出了姜变变压器零序过流保护的优越性。     

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.