浅谈电力系统二次设备信号干扰的预防和抑制

电厂、变电站侧量仪表、继电器等装置受电场，磁场的影响很大．分析了电力系统二次设备信号干扰的危害、来源。提出了有效的预防及抑制措施。     

干扰对DCS系统的影响及抑制

通过实例介绍了干扰对DCS系统作用的机理以及有效抑制干扰的方法。     

变压器局部放电故障诊断方法研究

电力变压器能否正常工作很大程度上决定了电网能否安全稳定地运行。我国的电网正在向大容量、高电压、高度灵活和智能的方向发展,对变压器性能的要求也在相应提高,所以变压器的故障诊断工作就显得尤为重要。局部放电既是变压器的故障表现形式,也是变压器绝缘结构损坏的诱因。本文首先介绍了变压器局部放电在线监测的研究现状、检测方法和模式识别的方法;然后对检测方法进行对比,分析其优缺点及适用范围;最后采用希尔伯特-黄变换进行局部放电脉冲信号的分析,并做出类型识别,经验证该方法是行之有效的。     

LGB-500干式电流互感器局部放电问题的分析与研究

近年来,干式电流互感器以其绿色环保、免维护等优点,逐渐受到用户的青睐.本文针对非运行中的干式电流互感器产品所存在的局部放电问题进行了深入的分析与研究,并通过大量的试验数据的比对,找出引起局部放电量变化的根源所在,并指出解决这一问题的思路和方法.     

典型局部放电模型声信号特性研究

脉冲电流法、空声超声局放检测、声纹局放检测是电力设备局部放电常用的检测方式.为研究典型放电模型的局放声信号特性,本文以上3种检测方法原理的基础上,搭建针尖模型、沿面模型声学检测实验系统,对不同曲率半径的针尖模型及不同导电膏长度的沿面放电模型进行声学测试.实验结果表明,空声局放检测、声纹局放检测对部分针尖放电模型表现出不...     

电力变压器局部放电带电检测及定位技术

随着我国社会现代化建设不断推进,电力企业也得到了迅速发展.电力变压器的使用频率越来越高,在电力变压器长期运行过程中,经常出现老化等故障问题.当电力变压器出现故障时,会产生变压器绝缘劣化,局部放电造成电力事故.为了提高电力变压器在使用过程中的安全性,在选择变压器时,要对变压器的局部放电进行带电检测和定位,也要对在使用中的...     

基于独立分量分析的发电机局部放电信号提取

发电机局部放电在线监测对于判断其绝缘状况意义较大,在研究发电机局部放电形成原因的基础上,研发了一套基于DSP的局放高速采集系统,提出了一种基于独立分量分析（ICA）的发电机局部放电信号提取方法,并通过实例证明了该方法的有效性。     

基于路径时间差的变压器局部放电超声定位方法研究

通过仿真详细阐述了超声波信号在变压器内的传播特性与传播路径。结合仿真结果,建立了变压器的数值节点模型,研究了超声信号非直达波路径与直达波路径的寻路算法。将两条路径的时间差作为特征参量与实测波形的时间差进行比对,采用粒子群优化算法迭代得到放电源的位置。在35 kV实验变压器上进行了定位实验,验证了算法的准确性。     

小波突变性检测技术在变压器局部放电超声定位中的应用

利用试验装置模拟电力变压器局部放电并对传感器接收的超声信号细节进行分析,发现局部放电产生的超声信号具有多个突变点,其中首次突变点是局部放电的起始时间,应当进行标记。但是传统的时延估计方法往往将信号突变峰值作为标记,定位的精度受到影响。小波突变性检测技术可以辨识信号的首次突变点,介绍了小波突变性检测技术的原理并利用该技术对试验装置的局部放电进行定位,结果表明该方法的定位精度明显提高,与传统方法相比定位的绝对误差可以减少1～2cm。     

超声波法和TEV法在开关柜局部放电测量中的应用研究

基于超声波法和TEV法的测量原理,对开关柜内不同形式局部放电的测量方法进行了研究。结果表明,设备表面放电和电晕放电通常会有较强的超声波异常信号,因此适合采用超声波法测量;对于设备内部放电,高频电磁信号可以通过绝缘不连续点传输到设备外壳而产生暂态对地电压,而超声波信号通过介质传播发生了较大的衰减,因此通常适合采用TEV法测量。此外,研究了不同的干扰源对两种测量方法的影响,并提出了减弱干扰影响的措施,可为工程实践提供借鉴。     

多功能局部放电检测仪的应用研究

介绍了基于超声波测量法的多功能局部放电测量设备的工作原理,以两个实例分析了多功能局部放电检测仪在实际应用中的可靠性.结果表明,该设备能够很好地检测和定位出利用其他局部放电检测手段无法检测到的局部放电信号,具有较高的可靠性.     

蓄冰槽盘管不完全冻结式内融冰与外融冰的取冷特性实验

为更有效地利用冰蓄冷的低温冷源，实验比较了不完全冻结式内融冰取冷特性与无扰动外融冰及鼓气作用下外融冰的取冷特性。结果表明，鼓气作用下的外融冰具有最佳的融冰释冷特性，出水温度低，取冷速率稳定，蓄冰槽的能量利用率明显提高。     

Analysis and suppression measures of lightning transient overvoltage in the signal cable of wind turbines

Lightning strikes are a major threat to the secure operation of wind turbines. When lightning strikes a wind turbine, the lightning current flows through the blade and the tower and then the induced overvoltage will damage sensors and signal cables. In this study, a comprehensive transient surge impedance model of a wind turbine was built to analyze the causes of the overvoltage in the signal cable. The model that studies the overvoltage caused by both capacitive coupling and electromagnetic induction included the blade, nacelle, tower, signal cable, power cable, and grounding system using π networks. The influences of the cable shielding layer, soil resistivity, and lightning current waveform on the overvoltage were also analyzed. Then, 2 overvoltage suppression measures, ie, grounding at 2 ends of the outer shielding layer and installation of a surge protective device, were tested. Results show that a signal cable with double shielding layers reduced the overvoltage in the signal cable, and higher soil resistivity resulted in increased voltage on the tower base. In addition, the peak and the front time of the lightning current significantly influenced the overvoltage on the tower and the cable. The effectiveness of the 2 suppression measures was also verified. The calculation results will provide guidance for a reasonable lightning protection design.     

光学方法在电力电缆局部放电测量中的研究现状

介绍了光学传感器的原理及其用于电气设备局部放电监测的依据,重点比较了基于Michelson、Mach-Zehnder和Fabry-Perot3种干涉原理的光纤传感器在电气设备局部放电检测中的应用。结合电力电缆局部放电超声波检测法目前存在的问题及发展方向,推荐了利用光纤Fabry-perot干涉法实现电力电缆绝缘在线监测的构想。     

机箱插件结构式测控装置中的共模干扰分析

以典型的机机箱插件结构式测控装置为对象，针对共模干扰沿传感器信号线侵入测控装置的测量插件并耦合到相邻插件的情况构建了简化等效电路模型，对共模干扰的传播进行了较详细的分析，根据分析结果提出了一些切实可行的抗共模干扰对策，并对插件间装设屏蔽钢板的利弊进行了讨论。     

宁夏汉延渠斗口闸孔出流的水力计算

分析了宁夏汉延渠斗口闸孔出流存在的主要问题。通过试验提出了闸后暗涵自由出流、淹没出流以及有压管流流态的判别方法,提出了相应的水力计算公式,可供工程采用。     

Discharge path observation and the statistical characteristics of discharge paths for long–air gap discharge for in‐operation wind turbines

When a wind turbine is in normal operation, the blades are rotating, and this blade rotation may affect the process of lightning striking the wind turbine. To investigate this problem, long‐gap discharge tests are performed in this study. Moreover, a multiple physical parameter synchronous observation platform is designed for a scaled wind turbine. Long‐gap discharge tests of a static and rotary‐scaled wind turbine with blade tip‐electrode gap distances of 1 to 8 m are conducted, and the discharge paths under different gaps and wind turbine operating conditions are obtained. The characteristic parameters—arc shape upon discharge, lengths of the downward and upward leaders, blade angle at the moment of discharge, and angle of upward leader initiation—are statistically analyzed. The analysis of the aforementioned data indicates that rotation has opposite effects on the discharge characteristic parameters under short and long gap distances. According to the analysis, blade rotation reduces the space charge density of the corona discharge near the tip, which leads to an increase in the field strength near the blade tip and a decrease in the field strength away from the blade tip. Short and long gaps have different degrees of influence on discharge, which changes the difficulty of upward leader initiation at the blade tip and consequently alters the entire discharge process. The obtained results can provide a reference for the lightning protection of wind turbines.     

Experimental study on partial oxidation of methane to produce hydrogen using low‐temperature plasma in AC Glidarc discharge

A reformer using low‐temperature plasma was designed and developed for hydrogen production. The reformer has three electrodes and uses AC gliding arc discharge. A reference condition, which is the highest hydrogen production, has a O₂/C ratio of 0.45, input flow rate of 4.9 l min^?1 and power supply of 1 kW. And the methane conversion rate, the high hydrogen selectivity and the reformer efficiency were 69.2, 77.8 and 35.2%, respectively. To investigate reforming characteristics, parametric studies were achieved for the gas components ratio, a gas flow rate, a reactor temperature, an input electric power and catalyst addition effect. The results are as follows: The gas components ratio was an important factor, which had maximum value. When the gas flow rate, the reactor temperature and the electric power were increased, the methane conversion rate and the hydrogen concentration also increased. Copyright © 2008 John Wiley & Sons, Ltd.     

Production of hydrogen from hydrogen sulfide assisted by dielectric barrier discharge

Hydrogen production by non-thermal plasma (NTP) assisted direct decomposition of hydrogen sulfide (H₂S) was carried out in a dielectric barrier discharge (DBD) reactor with stainless steel inner electrode and copper wire as the outer electrode. The specific advantage of the present process is the direct decomposition of H₂S in to H₂ and S and the novelty of the present study is the in-situ removal of sulfur that was achieved by operating DBD plasma reactor at ∼430 K. Optimization of various parameters like the gas residence time in the discharge, frequency, initial concentration of H₂S and temperature was done to achieve hydrogen production in an economically feasible manner. The typical results indicated that NTP is effective in dissociating H₂S into hydrogen and sulfur and it has been observed that by optimizing various parameters, it is possible to achieve H₂ production at 300 kJ/mol H₂ that corresponds to ∼3.1 eV/H₂, which is less than the energy demand during the steam methane reforming (354 kJ/mol H₂ or ∼3.7 eV/H₂).