光纤式GIS局部放电检测装置的研究

传统的GIS局部放电检测的方法主要是电测法和声测法,这些方法很容易受到现场环境的干扰。本文通过检测GIS内电晕产生的紫外光实现其内部局部放电的在线监测,介绍了非接触式紫外光功率检测法的基本原理及基于该方法的在线装置的基本构成和实现方法,并使用该实验装置对高压放电进行了模拟实验。结果表明,该装置具有很高的灵敏度和响应速度,具有很好的应用前景。     

无人机航迹中电力线电晕紫外探测与定位

在无人机电力线巡检中,为了能快速发现并定位绝缘子产生电晕放电现象的位置,对无人机航迹中的电力线电晕探测与定位方法进行了研究。分析了电晕放电功率检测模型,并得到放电源辐射出紫外光功率的公式。设计了具有高灵敏度的电晕探测设备,提出在无人机航迹中发现绝缘子缺陷的定位方法,通过两次不同角度对电力线铁塔探测,比较两次探测结果分析出缺陷绝缘子的位置。最后根据定位方法设计了对电火花和紫外LED探测实验。结果表明,该探测设备能准确探测出电火花产生的紫外光功率,受到紫外光在空气中损耗的影响,测量值随距离的增加而逐渐减小,且在不同距离情况下相对误差在11.5%之内。在紫外LED探测实验中,探测角度选择0°和15°时测量值较为准确。该方法在微弱电晕放电探测中准确有效,能够满足无人机在航迹中对电力线缺陷绝缘子的定位要求。     

变电设备智能物联超声局部放电微型化测量转换电路北大核心CSCD

针对变电设备智能物联监测中的分布式智能感知节点微型化设计需求,设计了一种新型的超声局部放电测量转换电路。使用高集成度仪表放大电路对高阻抗的超声局部放电传感器输出信号进行了低阻抗变换和固定增益放大,设计通带为20~300 kHz的宽带滤波电路以适应变电设备上带宽不同的传感器,最后通过增益可调仪表放大电路适应不同灵敏度的传感器输出信号。电路能同时连接2个超声局部放电传感器并对其测量信号进行转换,电路尺寸为83 mm×50 mm×15.5 mm。设计了相应的电路性能测试实验并给出了其在智能物联系统中的应用方法。实验结果表明:电路各级增益误差在整个通带频段内低于1%,1000倍增益条件下的输出端噪声RMS值不超过10 mV。     

应用于紫外检测技术的ICA图像融合算法

针对高压电气设备电晕放电故障点定位问题,对ICA图像融合算法、紫外检测技术和紫外成像系统等方面进行了研究。将ICA图像融合算法运用到高压设备电晕放电检测中,根据高压设备局部放电会发出紫外光的原理和紫外光波长在日盲200 nm~400 nm波段的特点,对高压设备局部放电区域采集紫外光图像和可见光图像进行图像融合,在融合图像中准确定位局放故障点。研究针对紫外图像和可见光图像灰度直方图差别大的特点,对传统Fast ICA算法进行优化,以优化后的权值对融合系数进行加权处理,建立融合规则使局放故障点表达更加清晰,并将算法运用于紫外成像系统。研究结果表明,改进后的Fast ICA算法对比于紫外成像仪的其他算法所得图像信息更加丰富、定位更加精准,融合图像可以有效地定位高压设备电晕放电故障点。     

振荡冲击电压下局部放电检测系统研究

为了研究振荡冲击电压下局部放电现象,设计了振荡冲击波形发生器,根据等效电路模型,推导出波形参数表达式;制作了一款专门用于冲击电压下局部放电脉冲测量的高频电流传感器,研究了线圈匝数和积分电阻对其频率特性的影响,利用函数发生器和方波电压源测试校准了传感器实际动态响应;在此基础上建立了一套局部放电脉冲测量系统,并对针板电极实验模型在振荡冲击电压下的局部放电信号进行测量.试验结果表明,该测量系统能够有效抑制源干扰,提取局部放电脉冲,为进一步研究振荡冲击电压下局部放电特征和机理提供重要价值.     

基于数字域TDI算法改进面阵CMOS图像传感器功能

为使面阵CMOS图像传感器具有TDI成像功能,研究了TDICCD的工作原理,提出了一种基于数字域的TDI算法,并讨论了如何利用FPGA实现该算法。该算法可在不改变CMOS器件构造的前提下,使其具有时间延迟积分功能。通过举例法推导出面阵CMOS图像传感器数字域TDI计算公式,并在此基础上优化了算法结构,优化后可以节省(m-1)(m-2)/2行内存空间。最后以航天相机为背景,讨论了地面像元分辨力、行转移时间与CMOS帧频的关系,通过一个算例计算出不同分辨力和积分级数条件下对CMOS帧频的要求。计算结果表明,帧频大于648frame/s的1280×1024CMOS,可以满足600km轨道高度下地面像元分辨力为1m的96级积分成像要求。     

对称式微波功率传感器的设计

为了克服传统微波功率传感由于失配和热损耗带来的微波功率测量误差,提出了一种基于MEMS技术的对称式微波功率传感器,对该微波功率传感器的微波损耗、温度分布以及微波功率的精确测量进行了研究.首先,根据提出的损耗模型推导了微波损耗功率和损耗电压的表达式,并建立了该传感器的传热解析模型;接着,设计并制作了该微波功率传感器;最后...     

局部放电紫外检测模糊推理量化分析系统

针对紫外放电检测存在巡检中不易被发现、紫外成像检测设备成本昂贵并且很难分析其放点强度等问题,对高压放电、无线通信、模糊理论等方面进行了研究,对局部放电紫外检测方法进行了归纳,设计了局部放电紫外检测模糊推理量化分析系统。为了适应不同传输的要求,系统通讯使用了有线传输到触摸屏、无线传输到附近的服务和通过GSM传输到手机进行监控3种传输方式。最后利用电视机里面的高压包模拟高压局部放电进行了实验。实验结果分析表明,该系统可以实时检测高压设备的放电状态,并可以得到设备的放电强度。     

用于微型胃肠道胶囊机器人供能的U型发射线圈无线能量传输系统设计与实验

为了解决微型胃肠道胶囊机器人或其他可植入医疗设备无法使用电源线供电以及无线能量发射系统性能差的问题,本文提出了一种新的U型发射线圈无线能量传输系统。与传统的螺线管对式的发射线圈相比,通过结构的改进,首次将磁芯加入到了发射线圈中。该系统可以极大地改善传输过程中传输效率低,机器人接收功率低的问题。本文建立了所提出的U型发射线圈无线能量传输系统的理论模型,并通过有限元模拟对其进行了分析。搭建了U型发射线圈无线能量传输系统平台对其能量传输效率和接收线圈的接收功率进行了测试,以验证所提出设计的有效性。实验结果表明,所提出的U型无线能量传输系统的传输效率最高达到14.13%,接收功率最高为3 780.75 mW,能够满足机器人工作的功率要求。     

一种基于矢量传感器阵的盲波束形成方法研究

本文针对水声环境和信号的特点，提出了一种基于矢量传感器阵的盲波束形成算法。首先建立了矢量传感器阵列接收信号模型，然后推导了基于矢量传感器阵列的波束形成最优权矢量的表达式。在此基础上，定义了接收信号的四阶累积量，进而盲估计了矢量传感器阵列的方向向量，实现了盲波束形成。该方法利用高阶累积量可消除高斯噪声干扰这一特性，有效地实现了基于矢量传感器阵列的盲波束形成。仿真实验验证了该方法的有效性和正确性。     

往复走丝电火花线切割高效低损耗切割研究

目前,高速往复走丝电火花线切割最高切割效率已突破200mm2/min,传统脉冲电源靠单纯提高脉冲能量来增加切割效率会导致钼丝损伤大、损耗加剧,短时间内就可能出现断丝。从脉冲电源的放电波形分析入手,分析了传统脉冲电源和高效低损耗脉冲电源的差异。研究认为,采用阶梯脉冲合理控制放电电流的前后沿,在加工中对非正常放电脉冲及时切断以减小对电极丝造成的损伤及损耗,采用等能量脉冲方式提高放电利用率等措施能大大提高切割效率,改善切割表面粗糙度,在切割效率190～200mm2/min条件下能实现长期稳定切割。     

Experimental study on energy consumption of energy-saving pulse power for WEDM

Wire electrical discharge machining (WEDM) is widely used in aerospace, mold manufacturing, automotive, and other fields. But now, traditional WEDM pulse power contains current-limiting resistor, and its energy utilization rate is low. Meanwhile, discharge energy of WEDM pulse power cannot be accurately controlled, and there is no unified understanding of distribution about discharge energy. In this paper, the pulse power improves energy utilization rate by removing current-limiting resistor and adopting single-arm pulse width modulation control method which controls peak current and modulates long short-circuit pulse width. Experiments proved that the energy-saving pulse power improves energy utilization rate by, approximately, 67.6 % than traditional pulse power. The paper analyzed a single-pulse energy waveform of the energy-saving pulse power and calculated each spark pulse energy and total energy provided by pulse power. It found that gap spark discharge energy only accounted for about 51 % of the energy provided by the pulse power, and other energy was mainly consumed in switching loss of power switch and parasitic resistance of pulse power.     

Local arc discharge mechanism and requirements of power supply in micro-arc oxidation of magnesium alloy

To study the requirements of the power supply in micro-arc oxidation (MAO) of magnesium alloy, many experiments were performed under the DC, unipolar, and ambipolar pulse output modes. Based on the experimental results and electric arc theory, the separate local arc discharge mechanism was put forward. It is considered that magnesium MAO process consists of three stages including anodic oxidation, micro-arc oxidation, and large-arc discharge in turn with increasing source voltage. The MAO film is composed of metal oxides that resulted from numerous discrete local arc discharges, which accumulate the non-equilibrium structure after undergoing sudden heating and cooling cycles. Separate local arc discharge is caused by the process in which the oxygen-based gas is ionized in the conduct channel bearing electric field intensity, changed from insulator to conductor that presents sharp negative resistance effect, and produced partially high temperature to ignite locally metal oxidation. The local arc discharge model is described as four courses: gas created from electrolysis, arc discharge, metals oxidization, and cooling and shrinking of oxides. The purpose of pulse supply is to inhibit the large-arc discharge by intervening proper cooling time, which cannot be actualized by a unipolar pulse mode because of the strong capacitive load characteristics but can be reached by an ambipolar pulse supply because the negative pulse period acts as cooling time. Using a discharge loop to remove the influence of load capacitive, a new type of pulse power supply for MAO is developed, so that the large-arc problem is resolved effectively, the film-forming efficiency is improved, and the pollution of the film and electrolyte caused by negative voltage is avoided.     

Arc discharge regulation of a megawatt hot cathode bucket ion source for the experimental advanced superconducting tokamak neutral beam injector

Arc discharge of a hot cathode bucket ion source tends to be unstable what attributes to the filament self-heating and energetic electrons backstreaming from the accelerator. A regulation method, which based on the ion density measurement by a Langmuir probe, is employed for stable arc discharge operation and long pulse ion beam generation. Long pulse arc discharge of 100 s is obtained based on this regulation method of arc power. It establishes a foundation for the long pulse arc discharge of a megawatt ion source, which will be utilized a high power neutral beam injection device.     

Local arc discharge mechanism and requirements of power supply in micro-arc oxidation of magnesium alloy

To study the requirements of the power supply in micro-arc oxidation (MAO) of magnesium alloy, many experiments were performed under the DC, unipolar, and ambipolar pulse output modes. Based on the experimental results and electric arc theory, the separate local arc discharge mechanism was put forward. It is considered that magnesium MAO process consists of three stages including anodic oxidation, micro-arc oxidation, and large-arc discharge in turn with increasing source voltage. The MAO film is composed of metal oxides that resulted from numerous discrete local arc discharges, which accumulate the non-equilibrium structure after undergoing sudden heating and cooling cycles. Separate local arc discharge is caused by the process in which the oxygen-based gas is ionized in the conduct channel bearing electric field intensity, changed from insulator to conductor that presents sharp negative resistance effect, and produced partially high temperature to ignite locally metal oxidation. The local arc discharge model is described as four courses: gas created from electrolysis, arc discharge, metals oxidization, and cooling and shrinking of oxides. The purpose of pulse supply is to inhibit the large-arc discharge by intervening proper cooling time, which cannot be actualized by a unipolar pulse mode because of the strong capacitive load characteristics but can be reached by an ambipolar pulse supply because the negative pulse period acts as cooling time. Using a discharge loop to remove the influence of load capacitive, a new type of pulse power supply for MAO is developed, so that the large-arc problem is resolved effectively, the film-forming efficiency is improved, and the pollution of the film and electrolyte caused by negative voltage is avoided.     

代码形式脉冲数字流的实现及意义

提出了一种新型的脉冲数字流，其量化单位可用二进制代码的形式进行改变或调节，从而使流体系统中的工作介质转变为真正完全的数字式流体。设计了代码形式的电一流体脉冲发生器。该种形式的脉冲数字流不但可以控制各种流体动力元件，使它们成为数字式的流体元件，而且可以对流体系统的负载流量、执行机构的工作速度等进行数字化的设定和控制，因而对于构建完全的数字流体系统、加速流体系统数字化的进程有着重要的意义。     

锶、钙离子复合激光放电电路的研究

在脉冲放电激励的锶、钙离子复合激光器中,分别对三种不同放电电路的电流脉冲波形进行了测量和分析,发现采用非对称Ｂｌｕｍｌｅｉｎ电路能有效消除放电电流脉冲后沿的振荡,有利于增加激光脉冲能量和激光平均功率。     

Design and experimental study of a power supply for micro-wire EDM

This paper presents the development and application of a new power supply in micro-wire EDM. A transistor-controlled power supply composed of a low-energy discharge circuit and an iso-frequency pulse control circuit was designed to provide the functions of high frequency and lower energy pulse control. Pulse states are classified as open circuit, normal spark, arc discharge and short circuit by means of the level of gap voltage and associated discharge current. A power supply test revealed that a high current-limiting resistance results in a decrease of discharge current. Peak current decreases with an increase of pulse-control frequency. Experimental results not only demonstrate that the iso-frequency pulse generator can provide low-energy pulses with a frequency of 185 kHz and a discharge current of 0.7 A, they also verify the applicability of the developed power supply in micro-wire EDM.