Design and Performance of a Novel Pancake Rogowski Coil for Measuring Pulse Currents

A novel pancake Rogowski coil without magnetic core is introduced in this paper. Owing to its special pancake winding structure, the coil is of low self-resistance and high self-inductance, and thus has excellent low frequency characteristic in the self-integral mode. Moreover, because of its unique installation method, the coil has a flexible sensitivity and can be applied under situations where toroidal air-core Rogowski coils or printed aircuit board （PCB） coils are not available. The parameters and performance of the pancake Rogowski coil are presented, and the principle of shielding is given. Measurements of step pulse current and oscillating pulse current by the coil are studied experimentally to illustrate its good linearity, reliable and flexible sensitivity and excellent frequency characteristic, especially its advantage in low frequency characteristic. The pancake Rogowski coil can be designed to assume round, square or rectangle shape, and has thus broad prospects in its application to the current measurement in such areas as plasma physics and pulsed power technology.

A Calibrating Device for Rogowski Coil Development

A calibrating device for the Rogowski coil is developed, which can be used to calibrate the Rogowski coil having a partial response time within tens of nanoseconds. Its key component is a step current generator, which can generate the output with a rise time of less than 2 ns and a duration of larger than 300 ns. The step current generator is composed by a pulse forming line （PFL） and a pulse transmission line （PTL）. A TEM （transverse electromagnetic mode） coaxial measurement unit is used as PTL, and the coil to be calibrated and the referenced standard Rogowski coil can be fixed in the unit. The effect of the dimensions of the TEM unit is discussed theoretically as well as experimentally.

Design of a Rogowski Coil with a Magnetic Core Used for Measurements of Nanosecond Current Pulses

A Rogowski coil is developed to detect the nanosecond pulse signals of the discharge current with a wide bandwidth of 800 kHz to 106 MHz and high sensitivity of 2.22 V/A. Performance tests show that the Rogowski coil has both excellent dynamic and static characteristics. Calibrating results and the comparison between the standard current shunt and the developed Rogowski coil for the measurement of nanosecond discharge pulses demonstrate that the developed Rogowski coil can reproduce the actual waveform of the discharge current accurately.

Detection of Partial Discharge in Power Transformers Using Rogowski Coil and Multiresolution Analysis

Partial discharge detection in power transformers is discussed using a new approach that exploit the broad band of the Rogowski coils and the potential of two signal processing tools： discrete wavelet transform and empirical mode decomposition. Detecting and analyzing incipient activities of partial discharge can provide useful information to diagnostics and prognostics about transformer insulation. So, partial discharge signals embedded in the electric current at ground conductor are measured using the Rogowski coil. These signals are submitted to noise suppression and the partial discharges waveforms are extracted through different ways： using discrete wavelet transform and using empirical mode decomposition. The comparison of these two methods show that the extraction with discrete wavelet transform results in a faster and simpler algorithm than the empirical mode decomposition. But this one produces more precise waveforms due its adaptive characteristic.

Typical application of Rogowski coils in inspection of electrobath

During the aluminum electrolytic roasting process,each component of the electrobath of aluminum performs unsteadily when the electrolytic bath is in the pre-roasting stage. It is important to monitor the currents of the anodes and the cathodes of the aluminum electrobath at regular intervals. Both practice and investigation indicate that Rogowski coil can be adopted to measure heavy direct current of the anodes and the cathodes of the aluminum electrobath. The paper not only introduces the typical application of the Rogowski coil to inspect the state of aluminum electrobath in the roasting process, but also analyzes the principles of the coil sensor including its dynamic properties and some important measurement results respectively. The optimal parameters of the coil can be simulated by means of an advanced simulation tool: simulink tools based on MATLAB soft environment. Based on the gathered current data, an even-current coefficient has been introduced, and the current curve can be drawn. Since they are applied in AL-Electrolyzing, it is possible to distinguish the anode of which the current is not evenly distributed, and to take adjusting measures over a period of time to ensure that the current is evenly distributed.

Air Cored Rogowski Coil for Measurement of Partial Discharges

A Rogowski coil was designed to measure partial discharge （PD） signal with low currents and high frequency. The possibilities of obtaining better measurements of PDs were explored by changing the inductance, mutual inductance, resistance, and capacitance of the coil. The designed Rogowski coil was calibrated under square wave voltage and arbitrary sine wave voltage. Then, according to the parameters of the Rogowski coil, the effect of changing some of these variables was simulated using a bode plot. Comparison shows that the simulation results were consistent with the experimental ones. A needle-plate in air gap model was set up and its PD under impulse voltage was measured. The results demonstrate that the Rogowski coil is adapted to measurement of PDs.

Modeling Rogowski Coils for Monitoring Surge Arrester Discharge Currents

Rogowski coils(RCs)are widely used to measure power or high frequency currents based on their design.In this paper,two types of RCs that are circular(traditional)and cylindrical shapes wound using wire covered by varnish are constructed.This construction is carried out to be suitable for monitoring the discharge current of the surge arrester installed in the distribution system.Concerning high frequency RC modeling for both types considering transfer function is introduced.Self-integrating for both types is attained.Therefore,the experimental tests using function generator for both coils are carried out to identify the parameters of the transfer function representing the introduced model.The measured signals for current and induced voltages are denoised for the parameter identification process.The denoised process is achieved using the MATLAB code‘wdenoise’while the parameters are estimated using the system identification toolbox.Verification of the proposed model is achieved using experimental results for the two coils.The sensitivity of the two coils is investigated based on the induced output voltage.The application concerning the two coils for monitoring the discharge current of the surge arrester is done.The results confirm the accuracy of the introduced RC model,as well as the performance of the cylindrical shape,is better than the traditional one.The simulation is carried out using MATLAB and ATPDraw programs.

Analysis on the Transfer Characteristics of Rogowski-coil Current Transformer and Its Influence on Protective Relaying

This paper systematically analyzes the transfer characteristics of the Rogowski-coil Current Transformer and its effect on protective relaying through theoretical analysis, experiments and simulations. The frequency characteristics and transient characteristics of Rogowski transducer and Rogowski-coil Current Transformer are deeply analyzed based on the physical structure of the transformer.?It is revealed that broad bandwidth of the transformer can improve the performance of protective relaying, and the bandwidth is determined mainly by the parameters of the Rogowski transducer and signal processing circuits. It is also discovered that the measurement errors of transient current mainly depend on the abilities for the current transformer to reproduce an accurate replica of the decaying dc components, which is mainly decided by the decay time constant of the aperiodic component of transient current and the parameters of the integral unit. Finally, some measures are proposed for the performance improvement of Rogowski-coil Current Transformer to meet the requirements of protective relaying system in terms of structural design and testing standards.

Experimental Evaluation of Rogowski Coil Performance for Locating PD in Energized Overhead Covered-Conductor Feeder

An experimental analysis is performed to evaluate Rogowski coil performance for PD （partial discharge） location on overhead CC （covered-conductor） distribution lines. The measuring set-up is arranged in high voltage laboratory. A multi-end measuring method is chosen as a technique to locate PD source point on the line. A power transformer is used to energize one end of the CC line by the AC voltage source. The performance of Rogowski-coil is tested in noisy environment. The tests are carried out conceming different measurement conditions such as off-line and on-line PD measuring systems. The results obtained from the laboratory measurements confirm the capability of the Rogowski-coil in order to measure and locate the high frequency PD source on the CC line in consistent with energizing AC source. Chirp detector is used as a signal-processing tool in order to extract the PD signals and then apply the locator algorithm.

Rogowski线圈电流互感器故障的早期诊断研究

Rogowski线圈电子式电流互感器(R-ECT)因其动态范围宽、绝缘性能好等方面的优势,逐渐成为智能变电站主流的电流计量设备,对其长期运行后的准确度评估也显得尤为重要。针对R-ECT早期表现出测量数据异常的故障,提出了一种基于样本自相关函数图和ADF单位根检验(augmented dickey-fuller test)的早期测量故障诊断方法。依据相位差不变原理和实测频率分布建立比对标准,通过相位差序列的平稳性检验实现R-ECT故障早期的测量误差诊断,为现场故障预警和调度决策提供参考,并通过实验验证了该方法的可行性。

In vitro effect of biologically active coating on endothelialisation of Nitinol coils designed for the closure of intracardiac shunt

Objective:To evaluate in vitro the effect of biologically active coating on endothelialisation of Nitinol coils designed for the closure of intracardiac shunt. Methods:Covalently binding procedure was performed with chemical vapor deposition (CVD). Heparin(200 IU/ml),r-hirudin(21 nmol/ml),or fibronectin(15 μg/ml),respectively, were bound to the basic coating(poly(amino-p-xylylene-co-p-xylylen)). In vitro tests were performed on five different coating groups(n=2 each):uncoated Nitinol, basic coating,heparin-,r-hirudin-,and fibronectin-coating. Human umbilical vein endothelial cells(HUVECs) were cultured in the presence of tested coils for 48 and 72 h. Adhesion of HUVECs were evaluated with light microscopy,and with confocal laser scanning microscopy after double-staining of vinculin,phalloidin, Ki67 and fibronectin. Results: After 48 and 72 h of incubation,except HUVECs around the basic coating showing abnormal morphology, HUVECs were able to grow next to all kinds of coils. By CLSM adhering cells were typically confined to maximal three secondary coil windings. HUVECs adhered best to the fibronectin coated coils,followed by the uncoated Nitinol. HUVECs barely adhered to the basic coating. The adhesion to heparin coating or r-hirudin coating was observed with various cell densities. Heparin coating seemed to support cell adhesion better than r-hirudin coating did. The HUVECs assembled fibronectin matrix on the fibronectin coating and uncoated Nitinol coil. Vinculin was expressed on both fibronectin coating and uncoated Nitinol as well, mostly diffused,but occasionally also in focal contacts. Ki67 expression was mainly noticed on the uncoated Nitinol coil and fibronectin coated coil,only occasionally on other materials. The densities and morphology of HUVECs, adhered to the correspohding well surfaces,were similar for all wells. The only exception was the well with the basic coating coil after three days of incubation. In this case, the cell density was diminished,and the cells became more elongated. The cells grown on the well surfaces exhibited a more profound matrix assembly and more pronounced focal adhesions than the cells adhered to the coil surfaces did. Conclusion:Except for basic coating,biologically active substance coated or uncoated coils show no acute cytotoxicity on HUVECs. Due to better cell proliferation,cell matrix assembling,and focal adhesion,only fibronectin coating improves the endothelialisation of Nitinol coils.

Toroidal Coil in Measuring Alternating Current at a Distance

This article discusses the use of a toroidal coil in measuring alternating current from a straight current-carrying wire passing perpendicularly through the coil. The sinusoidally oscillating current generates a sinusoidally oscillating magnetic field in its vicinity. This, in turn, induces a sinusoidally oscillating emf in the toroid. This (measured) emf can be used in order to calculate the magnitude of the electric current in the wire. The use of such technique might be sensitive to the location of the point at which the wire passes through the toroid. If the location is not known very precisely, this might cause errors in the value of the calculated current. We wanted to study if the result does not depend on the location of the wire at all, as is usually stated, or not. The study was done by deriving a single analytical formula for finding out the calculated current with the wire passing through any given point inside the toroid. This formula was then solved at more than 2300 points inside a toroid to see if the location of the wire affects the result or not.

Rogowski线圈的结构、电磁参数对其性能影响的研究

分析了Rogowski线圈结构参数(如线圈宽度、厚度和中心半径)和电磁参数(如线圈自感、互感和内阻)之间的关系以及它们对线圈动态特性(时域和频域特性)的影响。利用MATLAB软件和等值电路对Rogowski线圈进行了仿真研究。经过实验验证所得出的有关优选Rogowski线圈电磁和结构参数的方法,对于快速设计具有合理结构、最优电磁参数和良好动态特性的Rogowski线圈具有理论指导作用。

Rogowski线圈测量误差分析和估计

分析了在Rogowski线圈测量脉冲电流及电网短路电流时电路参数和线圈结构对测量准确度的影响,结果表明:用I1m=nim算式计算脉冲电流幅值I1m时将产生一定误差;利用简化方程确定短路电流大小时同样会产生误差;若线圈均匀缠绕于骨架,其输出信号不受一次电流导体位置和导体倾斜度的影响。修订了脉冲电流及电力系统短路电流的表达式,并以线圈结构变化为例进行了测量误差估计。

陡脉冲大电流的Rogowski测量线圈仿真研究

分析测量不同脉冲宽度电流的 Rogowski测量线圈的数学模型、时域和频域特性以及最佳阻尼参数配合和优选问题并比较了基于 MATL AB环境下 SIMU L INK工具所做的仿真结果和现场实验采集到的脉冲电流波形。提出了复合积分器电路模型 ,可用于优选 Rogowski线圈的电气和结构参数 ,有效抑制积分漂移 。

基于Rogowski线圈的电子式电流互感器暂态特性研究

旨在改善基于Rogowski线圈的电子式电流互感器的暂态特性,对Rogowski线圈分别配合理想积分器和实际电路中采用的非理想积分器进行了暂态特性仿真,仿真结果表明Rogowski线圈配合理想积分器时电子式电流互感器将有优良的暂态特性,但是如果非理想积分器参数设计不当,电子式电流互感器的暂态特性将被严重恶化。因此,提高积分电容容值或者反馈电阻阻值,将能改善电子式电流互感器的暂态特性。设定暂态电流衰减时间常数为标准IEC60044-8给定的最严格值,通过不同的参数配合进行仿真与比较,确定了一套能获得良好暂态特性的积分器参数。在此基础上,设计了一种由Rogowski线圈和改进的有源积分电路组成的电子式电流互感器电流传感元件。实验表明该电子式电流互感器电流传感元件具有良好的稳态交流测量精度,并能有效地测量暂态故障电流。

用于小电流测量的Rogowski线圈电流互感器

在用 Rogowski线圈测量电流时 ,国外通常把小于 1 0 0 0 A的电流测量统称为小电流测量。当 Rogowski线圈测量小于 1 0 0 A电流时 ,线圈所感应出的电压信号极其微弱 (仅为几 m V到几十m V) ,易受干扰而很难准确测量 ,因此 ,电力系统中研制用于小于或等于 1 0 0 A电流的 Rogowski电流互感器一直是公认的一大难题。文中介绍了一种通过后续电路的处理来测量小电流的新型Rogowski电流互感器 ,给出了其基本原理、实现和频率响应特性 ,最后就额定电流为 1 0 0 A的Rogowski电流互感器给出了实验结果。实验数据证明 ,其精度达到了 0 .2级。这种方法在测量额定值为几十 A甚至几

Rogowski线圈的高频特性分析

分析 Rogowski线圈频率特性的结果表明 :测量工频电流时线圈分布参数的影响可忽略 ,线圈的频率特性主要受积分器时间常数的影响 ;测量高频电流时线圈的分布参数对其高频频率特性影响较大 ,且要考虑连接线圈到积分器的同轴电缆、被测电流载体在线圈内的相对位置对其高频特性的影响。实际应用时可把线圈的参数带入到相应的方程得出其高频特性曲线 。

分布电容对Rogowski线圈动态特性影响研究

在简单分析测量脉冲电流的微分式Rogowski线圈的工作原理基础上,详细论述了Rogowski线圈分布电容的计算方法、测量原理以及分布电容对线圈动态特性(即时域和频域)影响机理。为确保传感器具有良好的动态特性,必须串接最佳阻尼电阻,给出了最佳阻尼电阻的计算方法。仿真和现场测试结果表明,本文提出的方法,对于设计具有合理电磁参数Rogowski线圈,确保传感器具有较好的动态特性,起到理论指导作用。

基于Rogowski线圈的电子式电流互感器复合误差计算方法

电子式电流互感器复合误差的计算与分析是提高获取电力系统运行信息精度的重要内容。为了准确测量电子式互感器的复合误差,介绍了电子式电流互感器的误差校验方法,分析了基于Rogowski线圈的电子式电流互感器基本工作原理,从而提出了多种基于Rogowski线圈的电子式电流互感器的复合误差计算方法。在此基础上对各种复合误差计算方法进行比较与分析,提出了基于Hilbert变换的复合误差计算方法。结果表明:Hilbert变换在信号为标准正弦信号时,计算结果不受采样频率的影响,当信号频率在常见范围内波动时,计算结果都能满足误差限值要求,即使信号出现一定谐波含量,也能达到准确度要求,因此选择Hilbert变换作为基于Rogowski线圈的电子式互感器复合误差计算的积分算法。实际检测证明基于Hilbert变换的Rogowski线圈复合误差计算方法是可行的。