高压高阻电桥的自检

介绍了HVRB－901型高压高阻电桥按元件自检的方法及其误差分析。     

高压高阻电桥研制成功

由能源部电力科学研究院研制的高压高阻电桥装置近期在京通过技术鉴定。该装置能进行高压兆欧电阻箱的检定、高压高值电阻的测量、高阻标准电阻的比较和量值传递、自我对比和检验等功能。该装置解决了高压高值电阻器在实际工作电压下不能测试     

高压高阻电桥装置通过技术鉴定

高压高阻电桥装置是为解决绝缘电阻表标准器—高压兆欧电阻箱的检定而专门设计的测量装置,也可用于其他高压高值电阻器的测试,还可用来比较高值标准电阻器。     

基于改进电桥法的10 kV电缆高阻接地

在深入研究分析电桥法原理的基础上,通过提高检流计灵敏度与提高电源电压两方面对传统电桥法进行改进,并研制了基于改进电桥法的成套设备。用该设备对多起电缆高阻故障进行了预定位,提高了10 kV电缆故障点预定位成功率,为供电企业快速、准确地查找电缆高阻故障提供了可以借鉴的方法。     

高阻箱在额定电压下的检测

分析了高阻箱在不同检定情况下标准电压源的逝定,及该原理的高阻箱检定装置的误差分析及检定注意事项。     

便携式双电桥校验仪的正确检定

便携式双电桥校验仪由高精度低阻十进盘和标准电阻盘组成,是检定便携式双电桥及各种毫欧计、微欧计的标准仪器。检定它的关键是对非十进小电阻以优于3×10-5的不确定度进行测量,这在直流计量中难度较大。本文指出了常用的电阻箱检定方法的不适用性,给出了四种正确的检定方法。     

直流高压高阻检定仪测量结果的不确定度评定

使用TY9801数字式直流高压高阻检定仪对直流高压高阻箱100Ω盘基本误差进行测量,通过直接测量的方法,分析了各项误差的来源,对直流高压高阻箱100Ω盘的基本误差测量不确定度进行评定。     

AT89C51单片机在单双电桥检定装置中的应用

介绍了AT89C51单片机在单双电桥检定装置中的开发应用。提出了AT89C51在电力仪表检定中的应用方法,阐述了ES-2010单双电桥检定装置的总体设计、实现和开发方法,并给出了系统电路和软件流程。应用结果表明,该装置运行稳定。     

高压高阻箱的自动测量与评定

高压高阻箱的检定工作重复而且繁重。为此。采用当前国际通行的观点和方法,编制了一套对高压高阻进行自动测量并对结果进行不确定度计算的软件。既提高了测量的效率和准确性。又避免了人工计算引起的误差。     

FA-200型变比电桥校验仪检定方法的研究

FA-200型变比电桥校验仪作为感应分压器类检定装置的经典仪器,在各计量部门和电力系统中被广泛应用。对FA-200型变比电桥校验仪原理进行分析,对其检定方法进行研究,给出N/9选点法,提高了感应分压器类变比电桥检定装置的检定效率。     

220 kV金属氧化锌避雷器不拆高压引线的预试方法

论述了通过合理接线实现220kV金属氧化锌避雷器(MOA)不拆高压引线预防性试验的原理和方法,将实测容城2#变220kV桥MOA的绝缘电阻、直流1mA电压U1mA及75%U1mA电压下泄漏电流的结果与拆高压引线试验数据对比,证明该法准确、高效、切实可行。     

电力电缆线性高阻击穿故障的特点及定位方法

交联聚乙烯和聚氯乙烯绝缘电力电缆的大量应用中,出现了一种新型的高阻击穿:其等效电阻相当稳定,用兆欧表500 V至5000 V档测量,击穿点绝缘电阻几乎不变,该类击穿点也许不能承担高电压,但很难降低其电阻,即使施加高压脉冲也无法击穿,因此难以通过脉冲电流法,乃至二次脉冲法、三次脉冲法定位。该类高阻击穿故障被定义为线性高阻击穿故障,是目前公认的定位难点。本文详细讨论其形成的原因,定位方法等。结论是:线性高阻击穿可以使用高压定位电桥直接定位;或通过合适的烧穿源降低绝缘电阻,再使用电桥或波反射法定位,关键是烧穿源必须有足够高的电压及功率。     

交流电阻及其时间常数的准平衡式电桥精密测量技术

研究了一种基于准平衡式电桥的交流电阻及其时间常数精密测量方法。电桥以双级感应分压器为比例参考标准,利用电子线路将电桥不平衡差值电压转移至变压器绕组,自动实现电桥准平衡状态,消除了感应分压器比例绕组内负载的影响。将数字同步采样测量方法应用于阻抗测量,实现了交流小电压复数比的准确测量。采用电子式引线电压补偿技术和开尔文网络消除了小电阻测量时串联导线的影响。研制的交流电阻及其时间常数测量装置可测量1~10 000Ω范围内交流电阻,测量频率为1 k Hz时实验结果表明,测量装置具有较高的准确度和稳定性。     

25kV高精度直流负高压源设计

介绍了一种用于工业分析的高精度直流负高压电源,电源输出电压25 kV,最大输出电流100 mA。电源通过BOOST电路校正功率因数和调节电压,用移相全桥把直流电逆变成高频方波,然后经高频变压器升压后倍压整流得到直流高压。用特殊材料和工艺设计制作的高频高压变压器解决了分布参数影响和绝缘耐压等难题,满足了高频高压和大功率输出的需要。实验运行表明:该装置输入功率因数高、输出电压稳定、纹波系数小。     

修正非线性误差的宽量程多电桥电阻测量电路设计

利用电桥测量电阻是各种自动控制和检测系统中广泛使用的一种方法,其测量精度和范围成为测量电路设计的关键技术。为解决传统单电桥电阻测量电路在宽量程范围内进行高精度测量的问题,通过对单电桥待测电阻与输出电压之间变化关系的分析,指明了等效电压与实际电压之间的非线性误差,提出了一种查表式修正非线性误差的方法,并给出了在线性公式基础上修正非线性误差的计算公式以及测量精度计算公式,在此基础上设计了一种基于单片机控制的可根据待测电阻值区间自动进行切换的多电桥电阻测量电路。该电路能够在较宽的量程范围内取得较高的测量精度,与传统的手动档位仪表相比较具有更好的便捷性和准确度。     

H桥级联型多电平高压变频器的断路故障分析

H桥级联型多电平高压变频器具有良好的技术发展前景。介绍了它的工作原理,从理论上分析了在两种工况下出现断路故障后变频器的运行状态,最后利用PSIM软件仿真验证了理论分析的正确性。从而为采取相应的保护措施提供了可能性,对于高压变频器的产品研发也具有一定的指导意义。     

Implementation of a Soft Switching Converter with High Input Voltage

This paper presents an interleaved zero voltage switching (ZVS) DC/DC converter with high input voltage applications. In order to reduce the voltage stress of MOSFETs, two half‐bridge zeta converters are connected in series at high voltage side. Thus, the voltage stress of MOSFETs can be clamped at one‐half of input voltage. Asymmetric pulse‐width modulation (APWM) is adopted to control power switches. With the resonant behavior by the leakage inductance of transformer and the output capacitance of MOSFET at the transition interval, MOSFETs can be turned on at ZVS. For each half‐bridge zeta converter, two series transformers are connected in series at the primary side and in parallel at the secondary side in order to reduce the current stress of secondary windings for high load current applications. Interleaved PWM scheme is used to control two half‐bridge converters in order to reduce the size of output filter inductor and capacitor due to the partial ripple current cancellation. Experimental results, taken from a laboratory prototype rated at 1 kW, are presented to demonstrate the converter performance. Copyright © 2012 John Wiley & Sons, Ltd.     

高低压整流桥式励磁控制方案及仿真分析

研究了一种适合于三峡特大型机组的高低压整流桥式励磁方案,该方案既能保证强励时励磁电压具有很高的顶值倍数,又能解决额定运行时因触发角过大所带来的问题.具体研究了适合高低压整流桥的2种工作模式:高低压桥同时承担正常励磁任务的工作模式;低压桥单独承担正常励磁任务的工作模式.针对三峡机组,对2种工作模式及传统励磁模式下的励磁电压换相次数及谐波畸变率进行了分析,得出三峡机组采用高低压整流桥式励磁方案时,应优先选择第2种工作模式.进一步的暂态过程仿真表明,高低压桥自并励系统能较好地满足三峡机组的实际需要.     

Analysis and Implementation of an Interleaved ZVS Converter with High Input Voltage

An interleaved half‐bridge converter is presented for high input voltage application. The features of the proposed converter are zero voltage switching (ZVS) turn‐on for all active switches, ripple current reduction at output side, load current sharing and load voltage regulation. Two half‐bridge converters connected in series and two split capacitors are used to limit the voltage stress of each power switch at one‐half of input DC bus voltage. Thus, active switches with low voltage stress can be used at high input voltage application. On the other hand, the output sides of two half‐bridge converters are connected in parallel to share the load current and reduce the current stresses of the secondary windings and the rectifier diodes. Since two half‐bridge converters are operated with interleaved pulse‐width modulation (PWM), the output ripple current can partially cancel each other such that the resultant ripple current at output side is reduced and the size of output inductors can be reduced. In each half‐bridge converter, asymmetrical PWM scheme is used to regulate the output voltage. Based on the resonant behavior by the output capacitance of MOSFETs and the leakage inductance (or external inductance) of transformers, active switches can be turned on at ZVS during the transition interval. Thus, the switching losses of power MOSFETs are reduced. The proposed converter can be applied for high input voltage applications such as three‐phase 380‐V utility system. Finally, experiments based on a laboratory prototype with 960‐W rated power are provided to demonstrate the performance of proposed converter. Copyright © 2012 John Wiley & Sons, Ltd.     

Development of the DC superimposition bridge method for the measurement of high insulation resistance of medium voltage XLPE cables in operations

The method for measuring insulation resistance by superimposing the dc voltage has potential for detecting the deterioration of cable insulations. The deterioration of cable insulations can be detected by measuring current which flows through a grounded shielding wire. However, the earth current also flows from the cable sheath into the grounding wire as noise. Thus, to assess the deterioration properly, it is necessary to separate the earth current from the total current. On the other hand, to improve detection sensitivity, it is desirable to superimpose the highest possible dc voltage. In this case, provision must be made so that there are no adverse effects on the GPT. The authors, placing special emphasis on the method of measuring high insulation resistance by configuring the bridge, have conducted an investigation on how to detect the insulation deterioration with high accuracy and sensitivity without impairing the functions of the GPT. The following issues were investigated and the results are reported in this paper: (1) It is possible to measure insulation resistance as high as 100,000 MΩ by superimposing 50-V dc through the GPT after cancelling the earth-current and by configuring a bridge for determining insulation resistance from voltage ratio. (2) Even if 50-V dc is superimposed through the GPT, it is possible to prevent the magnetic saturation of GPT if the current injected by such superimposition is limited (i.e., below max. 5 mA). (3) In lieu of a variable resistor, a variable dc voltage supply is employed in the bridge. The variable dc voltage supply requires no mechanically driven part, thus making it possible to realize a fully automatic monitoring system.