An accurate system for onsite calibration of electronic transformers with digital output

Calibration systems with digital output are used to replace conventional calibration systems because of principle diversity and characteristics of digital output of electronic transformers. But precision and unpredictable stability limit their onsite application even development. So fully considering the factors influencing accuracy of calibration system and employing simple but reliable structure, an all-digital calibration system with digital output is proposed in this paper. In complicated calibration environments, precision and dynamic range are guaranteed by A/D converter with 24-bit resolution, synchronization error limit is nanosecond by using the novelty synchronization method. In addition, an error correction algorithm based on the differential method by using two-order Hanning convolution window has good inhibition of frequency fluctuation and inter-harmonics interference. To verify the effectiveness, error calibration was carried out in the State Grid Electric Power Research Institute of China and results show that the proposed system can reach the precision class up to 0.05. Actual onsite calibration shows that the system has high accuracy, and is easy to operate with satisfactory stability.     

An innovative combined electronic instrument transformer applied in high voltage lines

For better performances, electronic instrument transformers are used to replace conventional electro-magnetic inductive current or potential transformers based on ferrous cores and windings to measure heavy current and high voltage in power system. But unpredictable stability, high price and unsatisfactory life hold back their industrializations. Employing the simple but reliable insulation structure of conventional transformer and the unconventional sensing methods of electronic transformers at the same time, an innovative combined electronic instrument transformer is presented in this paper. Performances of the prototype are estimated through relative tests, and the novel design has low price, high accuracy, satisfactory stability, very wide frequency response and long operation life, and therefore is well adapted to any voltage level up to 750 kV.     

高压试验中变压器试验问题的探讨

论述变压器绝缘试验中温度、升压速度、极性、铁心是否接地对绝缘试验结果的影响，并分析产生这些影响的原因。     

电子式电流互感器数据采集系统的研究

为了更好地适应电力计量系统数字化发展的趋势,设计了一种新型的电子式电流互感器数据采集系统。采用高速数字信号处理器(DSP)TMS320F2812芯片,外接14位的AD7894和信号调理电路,为了更好、更快地进行信号传送,DSP和AD7894之间采用光纤传输。给出了A/D控制程序流程图、仿真波形,并分析了测试结果。该系统具有强大功能的芯片和效率更高的软件使系统增强了数据采集和数据传输的速度和精度。该数据采集系统具有低功耗、高性能及良好的电隔离性。试验结果表明,测量精度符合IEC0.2级标准。     

低压电流互感器综合自动检测装置机械设计与实现

为解决低压电流互感器型式检验中电气试验人工操作过程频繁、劳动强度大、易发生误操作、电气接触不可靠及存在不安全、效率低、影响检测质量等问题,设计开发出了一种适用于实验室的多功能自动检测装置。装置设计为1个 "控制单元" 加2个 "检测单元" 的 "1+2" 一体化组合式结构,可同时检测两种规格互感器,实现了多品种互感器异步/并行多作业模式检测。结果表明,新型检测装置设计方案可行,运行可靠,达到了预期目标。     

基于连续高压脉冲方波的绝缘老化试验系统

为研究牵引逆变器输出脉冲电压对变频牵引电机绝缘的影响,根据牵引逆变系统电压波形和加速老化试验原则,采用变压式试验电源研制了一套基于连续高压脉冲方波的绝缘老化试验系统.高压脉冲电源为双极性,脉冲电压峰峰值为0～10 kV,频率为500 Hz～20 kHz,占空比为50%,上升沿时间2 μs左右,输出功率1 kW,温度范围为室温～300 ℃,高压脉冲电源脉冲幅值高、频率可调,具有过流、过压保护功能,完全满足进行变频牵引电机绝缘材料性能试验的要求.     

Characteristic analysis of shunt for high voltage direct current measurement

The resistive shunt is generally used as a sensor in the high voltage direct current (HVDC) system. The high frequency alternating current has an impact on the performance of the shunt owing to the skin effect and proximity effect causing DC measuring errors and even leading to protective system false operation. The impact of skin and proximity effects on the squirrel cage shunt is discussed in the paper. Numerical evaluation of the two effects is applied. The calculation results show that the value of the shunt resistance is dependent on the current frequency. Adequate selection of the radius of the conductors and the distances between conductors can greatly reduce the influence of the two effects on DC measurement accuracy. The field data of practical shunts during nominal operation and transient process confirm the results.     

An electron-microscope-based system for accurate microdimensional measurements

Calibration measurements of linear dimensions in the range 0.1 to 100 μm are provided by a high-resolution, scanning electron microscope-scanning specimen stage system. Computer-controlled, with a stationary sem electron beam and interferometric measurement of stage position, the system can provide point-to-point measurements accurate to 0.01 μm. It also forms the basis for development and certification of calibrated standards for planar objects, particles, and other microscopic objects and features     

750 kV电容式电压互感器现场检验系统的研究

针对目前750 kV电容式电压互感器(CVT)测试中传统比较测差法和"低校高"法存在的问题,研究并开发出750 kV CVT测试和检验系统。通过对750 kV CVT的工作原理、等效电路和误差组成的分析,提出了750 kV CVT空载误差、负荷误差的测试方法和测试线路,研制了30.6 kV带升压器标准电压互感器、变频电子电源和低频互感器检验仪,组成了一套完整的检验系统。通过现场试验,测试数据准确可靠,可以满足0.2级750 kV CVT量值溯源的要求,具有较高的实用和推广价值。     

一种新型的高压电器温度在线测量系统

基于螺旋形液晶填充光子晶体光纤的温度传感特性,提出一种新型的高压电器温度传感器系统。该传感器系统由宽带光源、螺旋形液晶、光子晶体光纤、光纤F-P腔(Fabry-Perot cavity)滤波器、信号处理放大电路等组成。将螺旋形液晶封装在光子晶体光纤的纤芯空气孔中,利用光子晶体光纤对温度和弯曲不敏感特性以及螺旋形液晶的螺距对温度变化非常敏感的特性,传感器的选择反射光波长依赖于温度的变化,采用光纤F-P腔滤波器解调出光波长的变化,利用反射波长与温度之间的关系,实现温度的测量。测量系统选用合适液晶,可以得到不同的温度测量范围,能对高压电器温度进行在线检测,测量精度可以达到±0.1℃以内,并具有本征安全、高精度、高电绝缘和抗电磁干扰、对应变和环境光变化不敏感以及与普通传输光纤兼容性好等优点。     

高压电气试验仿真系统设计

提出一种以计算机为主控平台,采用单片机、集成电路、无线通讯等低压电子技术实现高压电气试验系统仿真的方法.该方法使高压电气试验技术人员在低压工作环境下逼真模拟高压试验过程,安全可靠,同时便于实施系统培训,开展特殊故障查找与维修,以提高培训人员的技术水平.     

高量程加速度计动态线性校准系统

设计了双弹头霍普金森杆用于精确标定高g值加速度计的动态线性参数。基于一维应力波传播理论和弹性波叠加原理,分析了双弹头霍普金森杆为不同尺寸时对获取所需激励加速度信号的影响。利用ANSYS/LS-DYNA有限元仿真软件对不同设计条件下双弹头霍普金森杆的冲击效果进行了仿真分析。通过对不同影响因素的对比,确定了结构参数,设计了直径为30mm,长度为1 200mm的双弹头霍普金森杆,即高量程加速度计动态线性校准系统。利用设计的双弹头霍普金森杆对高量程加速度计进行了动态线性校准和试验验证,结果显示加速度计动态线性误差在5%以内,证明了设计的装置可对高量程加速度计进行动态线性校准,校准结果基本满足冲击校准的要求。     

Drive-crank load for a continuous mechanical transformer

The drive-crank load is calculated for a continuous mechanical transformer. Its magnitude and direction are determined with respect to a crank with a specific working radius.     

变压器原边电压不等并联运行时的环流分析

分析了变压器原边电压不等并联运行时存在的环流现象,给出环流的计算方法,提出了保证变压器并联运行的条件;空载环流与额定电流的比值（Ic/IN）小于10％,变压器原边电压差（U1-U2）不大于0．2kV。     

一种电磁式电流互感器的数据实时修正法

针对电磁式电流互感器存在着磁芯饱和区域的非线性误差问题,提出一种非线性区域的测量数据修正计算法。该算法对非线性区域的数据进行曲线拟和,在此基础上导出了一个简单的修正公式。在实时测试时,测试值通过修正公式的计算,可快速、准确地换算出所测实际电流值。对一电流互感器进行实测,经过对实验数据修正后的验证,证明了该方法的实用性和有效性。由于同类同规格的电流互感器的输入输出特性差异很微小,因此修正公式还具有一定的通用性。     

石材超声波精雕系统

本文提出了石材精密雕刻的新方法,设计了超声波精雕系统,解决了石材雕刻中微小异形表面高效精加工的难题,并对雕刻机理进行了研究。     

In-situ measurement of the current transformer burden in a current transformer testing system using a shunt resistor

Both the ratio error and phase angle error of a current transformer (CT) are significantly affected by the CT burden connected in series to the secondary terminal of the CT. Thus, the precise measurement of this CT burden is required for the evaluation of the CT errors. A method for measuring the CT burden in-situ in a CT testing system (CTTS) has been developed by employing the non-reactive type shunt resistor. For the measurement of the CT burden, the shunt resistor was connected in parallel to the secondary terminal of the CT under test in the CTTS. The burden values represented by the apparent power and the power factor can be calculated from the resistance (and reactance), which was obtained by measuring the ratio error (and phase angle error) as a function of the resistance of the shunt resistor. The uncertainties in the measurements of the apparent power and the power factor for the rated burdens studied were found to be less than 2.1%. The CT burden values obtained using our method were consistent with those measured using a digital multimeter within the corresponding uncertainties.     

小电流接地系统中变压器空载时电压不平衡原因分析

黄骅港是我国跨世纪重点工程,是西煤东运的第二大出海口,也是神华集团系统工程的重要组成部分,黄骅港的安全正常运转关系到集团的整体利益甚至会影响到国家经济的正常运行。黄骅港110kV供电站负责全港的供电,在整个港口的正常运行中起着至关重要的作用。     

高压直流UPS电源的研究

针对传统通信基站UPS供电电源存在的系统结构复杂、电源效率低、可靠性差的问题,研究采用了一种两级结构的高压直流UPS电源。在电路结构方面,电源前级采用了T型三电平整流电路,改善了输入功率因数和输入电流THD;后级采用了输入串联输出并联型全桥电路,并采用交错并联技术,减小了输出电流纹波。在控制方面,引入了负载电流前馈控制,提高了电源的动态响应速度,保证电源在负载剧烈波动时输出电压纹波很小。研究结果表明,高压直流UPS电源的最高效率为96%;其负载突变时恢复时间小于200μs,电压波动小于5%,动态响应快,输出特性好。     

纯电动汽车高压回路安全监测系统设计

针对纯电动汽车高压回路的安全监控问题,对纯电动汽车高压回路的配置、绝缘检测、预充电、高低压保护、高压环路互锁等方面进行了研究,对纯电动汽车驻停过程中高压回路的故障诊断与安全控制策略进行了归纳,提出了一种基于STM32 ARMCortex-M3内核单片机以及CAN总线技术的监测系统,利用高压直流试验台对纯电动汽车的绝缘电阻以及发生故障时高压断路响应时间进行了测试.研究结果表明,该系统能实时监测高压系统的各项电气参数,能够实现绝缘检测、预充电、高低压保护、高压环路互锁等多项功能,系统故障断路响应迅速、可靠性高.