一种新型低值宽带无感分流器时间常数测量方法

高压脉冲或电力系统中的高频谐波通常采用宽带无感分流器记录瞬态电流波形。分流器的带宽取决于其时间常数, 进而可用于评定其引入的测量不确定度。利用高精度数字多用表测量得到分流器的直流电阻, 通过同步采样方波输入电压以及被测分流器两端的输出电压, 利用最小二乘拟合算法直接计算得到被测分流器的残余电感, 据此确定分流器的时间常数。同步采样采用2根等长电缆与信号发生器的输出进行连接, 避免了信号的传输时延。研究了阻抗匹配对电缆电阻所造成的方波电压和分流器输入端电压差异的影响。结果表明该测量方法可以直接测量阻值1Ω以下、带宽10MHz以下低值无感分流器的电感与时间常数, 成功地解决了宽频电流传感器及宽带无感分流器量值溯源难题。     

100kA快响应精密冲击分流器研制及特性分析

冲击电流为暂态电流波形,持续时间短且波形不可重复,测量误差影响因素众多难以评估.研制快响应精密冲击分流器,采用同轴管式结构,分析分流器的测量原理及尺寸设计.研究分流器的瞬态响应过程,将输出信号焊接至电阻体外侧,消除趋肤效应的影响.分流器的稳态电阻测量值为0.969 7 mΩ,杂散电感为32 nH,测量额定电流时,电阻温...     

电机定子匝间绝缘测量用冲击分压器性能试验研究

在研究电机定子电气性能检验装置校准方法项目过程中,研制了一种采用高压无感电阻、等电位屏蔽措施、二级分压结构和分布电容调节技术的冲击分压器,它被用于电机定子匝间绝缘项目的冲击电压峰值和波前时间的测量。经过试验,该电阻分压器的分压比误差小于0.5%;上升时间小于100ns,满足测量指标要求。     

一元线性回归方程在大电流分流器测量中的应用

主要分析了在电力系统测试中温度对大电流分流器测量的影响，阐述了统计学中一元线性回归方程的原理、求解方法及作用；在实际应用中利用线性回归方程解决了大电流分流器测量中温度带来的影响，该方法对科研试验的测量问题具有指导作用。     

双电桥测量的应用

双电桥作为一种测量电路迄今主要用于测量小电阻,然而它的测量作用远不止此,本文将介绍使用双电桥完成的一系列重要测量,如电压比例的比较与高值电阻负载系数的测量;低值电阻负载系数的测量与分流器在标称电流下的检定;用双电桥测量高值电阻等。     

智能型冲击峰值电压电流表的设计

由于目前国内外生产的测量冲击电压峰值的峰值表,其准确度为1%~3%,不能满足最新国家标准的要求,所以,要研制更高等级的冲击峰值电压电流表(以下简称峰值表)。该设计主要由输入衰减器、正反相极性峰值检波采样保持电路、A/D转换器(7135型芯片)、单片机系统、触摸液晶显示屏、锁存保持电路、复位/测量设置电路以及供电电源等部分组成。该设计可以直接测量其峰值电压不大于2kV的冲击电压,当外接用于测量冲击电流的同轴分流器时,被测的冲击电流通过分流器实现电流/电压转换,将冲击电流转化为冲击电压,实现测量峰值电流的功能。经过稳定性考核,可以分析得出准确度可以达到0.5%,完全满足实际使用的要求。     

电流监测器灵敏度误差的校准

提出以无感电阻为标准器,电流通过电流监测器及无感标准电阻,监测器输出端电压与无感标准电阻两端的电压差由示波器测得,即为电流监测器灵敏度的误差。以型号为2100的电流监测器为例,分别对稳态电流信号和暂态电流信号下监测器的灵敏度误差进行了校准。     

Rogowski线圈在高压脉冲大电流测量中的应用

利用Matlab软件的Simulink仿真环境,创建了高压脉冲大电流测量系统的仿真模型,实现对罗氏线圈结构参数的确立和积分器积分常数的优化.给出了一种适合于高压脉冲大电流测量的罗氏线圈的结构设计及其积分电路的设计方法,并将这种测量装置成功应用到脉冲成形网络(PFN)放电系统中.通过在积分电路中加入滤波抗干扰设计,实现了对高压脉冲大电流的测量,克服了冲击电流测量中常规用分流器存在的问题和不足.     

一种大电流测量系统的设计与应用

针对高频大电流的应用校准需求,提出了一种采用盘式分流器的大电流测试系统。盘式分流器结构采用同轴结构屏蔽外部干扰、减小趋肤效应,选用紫铜金属材料散热性能好,选用宽频大功率电阻减小温度漂移。数据采集卡高速采样可对100 A,10 k Hz电流相关参数进行精确测量。实验结果证明,该系统稳定性好,测量准确度高,可以满足高频大电流测试需求。     

基于分流器法和罗氏线圈法的静电放电电流测量一致性研究

本文旨在研究不同测量接入方式对静电放电电流测量的一致性,在分析静电放电电流的测量方法的基础上,着重阐述了分流器法和罗氏线圈法的测量原理,对其静电放电电流的测量进行了比对分析。试验表明：两种方法的静电放电电流测量一致性较好,对提高静电放电的防护性能,研究静电放电电流的精确测量具有重要的实际意义。     

Measurement of the resistive leakage current in surge arresters under artificial rain test and impulse voltage subjection

Surge arresters are installed on transmission and distribution lines and in substations between phase and earth in order to improve the lightning performance and reduce the failure rates. High-energy stresses and housing deterioration are the main factors of degradation and damage of surge arresters. Thus, there is need for testing and monitoring the electrical network?s arresters, in order to verify their good condition and their ability to effectively protect the lines. The most common method used, is the measurement of the arresters? total leakage current (with the isolation of the resistive part), which is an indicator of the arrester?s condition, since every change, deterioration or damage leads to an increase of the resistive leakage current. In the current work, the total leakage current of two 20 kV ZnO surge arresters without gaps is measured and the resistive component for three different cases (brand new arresters, measurements under artificial rain and measurements after impulse voltage subjection) is computed. The analysis of the produced results can be useful in correct diagnosis of arresters? condition and in more effective schedule maintenance, since any recorded high-resistive currents do not necessarily result arrester?s repair or replacement.     

防雷标准与防护措施研究

该文针对防雷标准,从直击雷保护、感应雷防护、合理布线、屏蔽、共用接地系统、等电位连接、加装电涌保护器等方面研究雷电防护措施,使建筑物受雷击的损害降到最低程度。     

Simulation and analysis of metal-oxide surge block arrester dynamic characteristics

Metal-oxide surge arresters play an important role in protecting power system equipment doing lightning surges and switching surges. Especially, overhead transmission lines are often struck by lightning. This often results in line faults. These can be reduced effectively by installing lightning arresters. Recently, some simulation programs such as EMTP/ATP have been developed to estimate the benefits of the installation of lightning arresters. For those simulation programs, the arrester model is usually a non-linear resistor. As seen in many discussions from papers and theories, the ZnO arrester, which is the most popular, has the dynamic behavior of frequency dependence. In other words, the residual voltage of the arrester depends on the frequency of surge. The higher the frequency of surges, the higher the residual voltage of the arrester. In this article, the simulation results of four different frequency-dependent models examined by EMTP/ATP show relative maximum error lower than 9%, as well as the residual voltage of arrester being increased by 14% when the front time of surge is reduced from 8 to 1?µs. With these results, this article offers suggestions to use frequency-dependent arrester models for all corrective arrester simulations to enhance the accuracy of simulation programs.     

Statistical evaluation of lightning-related failures for the optimal location of surge arresters on the power networks

Direct lightning strokes cause unscheduled supply interruptions in power systems because of a failure of the insulation. Metal oxide surge arresters, as a proper protective device, have been widely adopted in power systems to reduce lightning initiated flashovers and, hence, increase the power quality and reliability of the systems. Based on a genetic algorithm approach, a cost effective solution is described to find the optimum location of surge arresters on a power network in order to minimise the global risk of the network, and to improve its reliability. A statistical approach to evaluate lightning failures has been introduced and an optimisation procedure developed to analyse the network in order to satisfy the power utility requirement for a specific value of risk and/or line performance with a minimum set of arresters, that is, at minimum cost. Not only the insulation flashover but also the failure of the arrester can affect the reliability of power systems. Therefore, both the failure of the insulation and that of the arrester are considered in the proposed method.     

Development and Implementation of Current Tee for AC High Current Calibration

Thermal current converters or thermal transfer standard with AC–DC current shunts act as the reference standards for accurate and precise measurements of low frequency current in the frequency range from 40 Hz to 10 kHz. At present CSIR-NPL, India has the AC–DC current transfer difference (δ _x) calibration facility upto 20 A. To extend our AC current calibration range from 20 A to 100 A, a current Tee for AC high current using LC connectors has been indigenously designed and developed. This paper presents the development of current Tee for AC high current calibration. The calibration results for assigning ‘δ _x’ at 30 A current shunt with respect to 20 A are shown and the same measurement technique has been used to extend the current range up to 100 A.     

An electromagnetic model of lightning return stroke channel using electric field integral equation in time domain

We use an electromagnetic approach based on antenna theory (AT) to evaluate the lightning return stroke current as a function of time and height. The lightning channel is modeled as a lossy, straight, and vertical monopole antenna above a perfectly conducting ground, which is excited by a source voltage at the base of the channel. This voltage source is a function of the current assumed at the ground level and the input impedance of the monopole antenna. An electric field integral equation (EFIE) is employed to describe the electromagnetic behavior of the antenna. The numerical solution of EFIE by the method of moments in time domain provides the time-space distribution of the current along the lightning channel. This AT model with specified current at the channel base requires only two adjustable parameters, namely the return-stroke propagation speed and the channel resistance per unit length. To demonstrate the accuracy of the proposed model, we compare it to the most commonly used models in terms of the temporal and spatial distributions of channel current and predicted electromagnetic fields. We also present results to show the effectiveness of the model in the analysis of lightning-related problems dealing with complex structures. In this regard, the lightning induced overvoltages on the neighboring overhead lines and the lightning strikes to tall structures are investigated.     

含紧固件复合材料层压板雷击后损伤及力学性能退化试验

以含金属紧固件编织结构碳纤维/环氧树脂复合材料层压板为研究对象,通过人工模拟雷电流试验,并结合目视观察、超声损伤扫描、微米X射线三维成像及高倍显微镜等损伤检测手段,对其在雷电流直接效应作用下的损伤模式、机制及特征进行了分析,同时,采用材料力学性能试验系统,对其雷击后的静拉伸承载能力退化程度进行了评估。研究结果表明：由金属紧固件引起的"雷电流分散效应"导致含紧固件复合材料层压板雷击损伤以分层损伤为主,且损伤沿层压板整个厚度方向分布;雷击损伤的产生存在一个雷电流强度门槛值,当雷电流强度小于该值时,层压板不会出现损伤;紧固孔周围的雷击损伤在静拉伸过程中会产生"应力分散效应",导致含紧固件层压板静拉伸承载能力随雷击峰值电流的增加先提高后下降。     

Coaxial Shunts as AC–DC Transfer Standards of Current

A new type of coaxial shunt, with nominal current ranges from 20 mA to 20 A, has been designed at the Istituto Nazionale di Ricerca Metrologica (INRIM). Depending on the nominal current, different construction methods have been employed. For current ranges between 100 mA and 20 A, the shunts are made using disk structures, either with surface mount (SMD) resistors or resistive layers. To reduce coupling, the structures have a very small magnetic interaction between the input current and the output voltage circuits, resulting in a flat response over a wide frequency range. This paper presents design and construction details of these shunts, as well as measurement results and plans for further development.