用于变压器油中乙炔含量检测的红外激光气体传感器的研制

为检测变压器油中溶解气体种类和含量,研制了一种红外激光气体传感器,介绍了相关检测原理和系统构成。该传感器有一种基于串联反射镜组的透射式吸收气室,在气室体积不变的前提下可增加吸收光程,以获得更高的检测灵敏度。以变压器油中溶解气体乙炔为研究对象,选择乙炔气体在1 529.16nm处的吸收谱线作为其峰值特征吸收谱线,并基于最小二乘法对乙炔气体体积分数进行定量分析。实验结果表明:当注入电流为100mA、温度为26°C时,激光器的输出波长为1 529.14nm,光强透射率稳定在88%,能够满足信号处理系统的要求。在一定乙炔气体体积分数范围内,传感器的吸光度与乙炔气体体积分数之间具有良好的线性关系,检测限为10-5。因此所研制的红外激光气体传感器能够有效检测变压器油中的乙炔。     

基于开放光路FLRDS技术的C2H2和C2H6气体检测

磷酸铁锂电池因其较长的使用寿命和环保性,被广泛应用于储能系统。然而,近年来,储能电站安全事故频发,给电网稳定运行造成了威胁。在热失控过程中,磷酸铁锂电池会产生C₂H₂和C₂H₆等可燃气体,是造成燃烧、爆炸等灾害的重要原因。因此,实时准确监测储能预制舱内C₂H₂和C₂H₆等可燃气体的浓度是保障其安全稳定运行的关键。文中提出一种基于开放光路光纤环形腔衰荡光谱(fiber loop ring-down spectroscopy,FLRDS)技术的气体检测方法,可实现自由空间内微量气体在线监测。对梯度折射率(gradient index,GRIN)透镜的空间光耦合光学损耗进行理论和实验分析,建立插入损耗为0.95 dB的开放光路FLRDS气体检测系统。根据C₂H₂和C₂H₆红外光谱特性,开展激光光源性能测试。模拟开放空间气体环境研究了C₂H₂和C₂H₆的气体浓度检测方法,结果表明,该系统具有较好的稳定性,N₂背景下测量信号标准偏差S仅为平均值的0.156%。衰荡时间与气体浓度之间存在良好的线性关系,C₂H₂线性拟合度R²为0.998 32,C₂H₆线性拟合度R²为0.994 72。反演计算结果表明,C₂H₂和C₂H₆的最大相对误差分别为3.215%和4.72%,最大绝对误差分别为16.86 μL/L和12.74 μL/L,测量精度良好。     

采用激光共振光声光谱技术检测乙炔气体

乙炔常伴随变压器内放电性故障的出现而产生,为了检测乙炔气体,通过研究乙炔在近红外波段的红外吸收特性及深入分析光声池的设计,构建了用以检测乙炔的光声光谱气体检测装置。利用该装置,对分布反馈半导体激光器的辐射特性进行了实验分析,结果表明,激光器的辐射波长随工作温度或注入电流的升高以近似线性升高,且在工作温度下的变化梯度大于注入电流下的变化梯度;利用分布反馈半导体激光器的窄线宽和可调谐特性,测得乙炔分子在近红外区第一泛音带的R(4)、R(5)支光声光谱;对光声信号受气体体积分数、激光功率影响的实验分析表明,在低气体体积分数、低激光功率条件下,光声信号与气体体积分数、激光功率间具有良好的线性依赖关系,该装置对乙炔的最低体积分数检测限约为1.4×10-6。     

多谱线TDLAS测温中谱线选择的实验研究

采用可调谐半导体激光吸收光谱技术,利用两条谱线可以测量激光路径上的平均温度。在利用多条谱线测量激光路径的平均温度时,测量的精确度主要受制于测量信号的离散程度以及谱线低能级能量的分散程度。利用中心波长为1392.5 nm(7181.32 cm~(-1))的激光器快速扫描4条H_2O的波数为7182.950、7182.209、7181.156、7179.752 cm~(-1)的吸收谱线,研究了不同的谱线组合方式对激光路径平均温度测量精密度的影响。实验结果表明,进行谱线选取时,通过依次去掉一条谱线并计算其余谱线测量标准偏差的结果,能够快速反映出被去掉谱线对温度测量精确度的权重。通过谱线选择,测量得到的路径上平均温度的标准偏差小于20 K。     

基于混合气体热特性的GIL氮气使用配比研究

SF₆存在全球变暖潜能值高,价格昂贵等问题,因此具有良好的绝缘性能和环境友好性的SF₆/N₂混合气体被认为是目前最具发展前景的SF₆替代气体。在保证气体绝缘输电线路(Gas insulated transmission lines,GIL)绝缘水平的前提下,对SF₆/N₂混合气体的热特性进行研究,确定不同条件下的SF₆/N₂混合比,对减少SF₆使用量,降低电力设备对环境的影响具有重要意义。因此,本文利用有限元分析法,建立电磁场-流体-温度场耦合的三维GIL模型,通过改变SF₆/N₂混合比、绝缘气体压力、负载电流和环境温度得到不同工况下的GIL热特性,从而确定SF₆/N₂混合比与温升之间的关系。仿真结果为GIL选择合适的SF₆/N₂混合比提供依据,具有良好的工程应用前景,对减少SF₆使用量,降低电力设备对环境的影响具有重要意义。#$NL关键词：GIL;SF₆/N₂混合气体;气体绝缘;有限元分析;热特性分析#$NL中图分类号：TM75     

基于SF6混合气体绝缘性能的设备补气策略研究

随着电力需求的增长和环境保护要求的提高,SF₆气体的使用逐渐受到限制。SF₆混合气体在一定程度上减少了SF₆气体用量,目前已经在电气设备中应用。文中针对SF₆混合气体在220 kV气体绝缘组合电器（GIS）中发生泄漏引起的绝缘变化展开研究,通过改变微量的气压值和混合比,探究混合气体的绝缘性能变化,分析气压、混合比因素对工频击穿电压的影响规律,获取各气压下各比例混合气体的绝缘强度曲线图,从而得到保证设备安全稳定运行的补气策略。研究发现,混合气体击穿电压的变化规律呈现出随着压强和混合比的提高,非线性程度增大的特点,并且得到了设备安全运行的混合比和气压的边界值。文中的研究可以为SF₆/N₂混合气体绝缘设备提供运维规程和技术标准,同时为制定混合气体的检测技术标准奠定基础。     

基于光声光谱峰面积的微量乙炔气体定量检测

乙炔是区分电力变压器过热性和放电性故障的标志性气体,其含量对判断电力变压器内绝缘故障类型和严重程度具有重要意义。为此,采用分布反馈式半导体激光器搭建了基于光声光谱峰面积的微量乙炔气体定量检测平台,选择乙炔分子1 529.18 nm处的吸收谱线,试验研究了分布反馈式半导体激光器输出峰值波长的温度漂移特性和乙炔气体的光声光谱响应特性,获取了基于Lorentz线型拟合的不同体积分数标准乙炔气体的光声光谱响应特性曲线,并基于最小二乘法对特性曲线峰面积与乙炔气体体积分数之间的定量关系进行了研究。结果表明:在气体吸收未饱和的情况下,乙炔气体光声光谱峰面积与其体积分数之间存在良好的线性关系,该试验平台对乙炔气体的检测下限为0.46×10-6。该研究结果为变压器油中溶解气体的在线监测及电力变压器内绝缘故障诊断奠定了基础。     

SF_6与N_2混合气体特征分解产物COF_2/N_2O的红外吸收特性

目前SF_6/N_2混合气体作为SF_6气体的替代气体已应用于许多电力设备中,而检测这些电气设备发生故障后生成的COF_2、N_2O等新分解气体有助于开展电气设备的故障诊断。为研究基于红外吸收特性的SF_6/N_2混合气体典型分解气体的检测技术,利用HITRAN数据库给出的吸收谱线强度、线型函数等参数,对典型组分COF_2、N_2O的红外吸收特性进行研究;得到了COF_2在波数400～2 000 cm~(-1)和N_2O在波数400～8 000 cm~(-1)范围内的红外吸收谱段、最强吸收处的中心波长、吸收系数峰值;并分析了压强和温度对COF_2、N_2O的强吸收谱的影响。结果表明:这2种分解气体在红外热辐射光源有效谱段1.2～10μm内具有较强吸收,可以用基于红外热辐射光源的光声光谱装置进行检测;且气体吸收谱线的吸收系数随压强的增大而增大,但不同气体增大程度不同;随温度的升高气体主要吸收谱段的峰值吸收系数减小,但也有部分吸收谱段交叠处的峰值吸收系数增大;COF_2、N_2O在运行条件(505 kPa,温度313 K)下的红外吸收系数大于标准条件(101 kPa,温度296 K)下,运行条件更利于气体检测。     

半导体激光器温度控制电路设计及实验研究

DFB可调谐二极管激光器是激光光谱测量系统中的最主要部件之一,它的输出波长与辐射功率的稳定性决定测量系统的稳定性.影响DFB可调谐二极管激光器输出波长和输出功率的因素主要为激光器的注入电流和工作温度,而工作温度对输出特性的影响更大.设计了激光器温度控制电路,并实验分析了PI参数对温度控制稳定性的影响以及温度控制的短期稳定性;将设计电路应用在DFB可调谐二极管激光器上进行激光器输出波长与输出功率的长期监测,得到激光器输出波长的标准偏差为0.2×10-6,输出功率的标准偏差为0.02 mW.     

基于可调谐激光吸收光谱技术的硫化氢检测方法研究

硫化氢气体在线监测对于控制其泄漏风险、保护环境十分重要。可调谐激光吸收光谱技术具有灵敏度高,速度快,特异性强等优点,在气体在线检测领域具有十分广阔的应用前景。研究了基于可调谐激光吸收光谱技术的硫化氢气体检测方法,及针对测量条件变化的校正方法。测量系统采用温度与电流调谐两种方式,不仅扩展了调谐范围,并且保证了调谐速率与稳定性,在锁相检测技术基础上,实现了气体吸收信号二次谐波分量提取。分析了气体压力与温度对于吸收光谱测量影响,提出了基于参数拟合的校正方法。实验结果表明,所研究的检测系统可实现硫化氢气体高灵敏检测,校正方法可有效消气体温度、压力等条件变化对于建模预测结果的影响。     

Development of optical ZCT and its application to fault section detection for 66-kV underground branch transmission lines

The optical ZCT (Zero-phase Current Transformer) which combines an optical magnetic field sensor with a magnetic ring core of silicon steel plates has been developed. Bi-doped YIG [Yttrium Iron Garnet, (BiYbGd)₃Fe₅o₁₂] having a large Verdet constant is used as a Faraday element. The optical ZCT detects the conductor current of 0 to 2000 A at high resolution and has been applied to the fault section detection system for 66-kV underground branch transmission lines which monitors a multiterminal line having Y-branch joint box in on-line state. Optical ZCTs and a section detector/indicator are connected with optical fibers which are capable of nonrepeatedly transmitting signals over 6 km, and allow monitoring long-distance underground power transmission lines. A developed system is now operating on the JR Kasai line (Shinkawa pump line) of Tokyo Electric Power Company.     

Gas discrimination method for detecting transformer faults by neural network

This paper describes a method available for early detection of abnormality in an oil-filled transformer. In this method, four gas sensors having different characteristics and neural network are used to identify gas species (H₂, CH₄, C₂H₄, C₂H₂ and mixture of two species). To improve the selectivity of gas sensors, the time response patterns induced by changing sensor temperature and the stationary sensor output are identified by neural network. Furthermore, the mixture ratio of gases is derived by using the stationary sensor output in response to the changing sensor temperature. Gas species are well discriminated, and the mixture ratio derived from the sensor output agrees well with the measurement by gas chromatography. Therefore, it is confirmed that our method is applicable to the transformer diagnostic technology.     

SF6压力对GIS典型缺陷局部放电检测灵敏度的影响

气体绝缘开关设备(gas insulated switchgear,GIS)内部气压是影响局部放电检测灵敏度的重要因素。在局部放电实验平台中构建尖端、悬浮、气隙与沿面缺陷模型,基于特高频法、高频电流法与超声法开展气压0.2~0.5 MPa下局部放电信号特征的检测实验,并对比了高频电流法和超声法局部放电检测的灵敏度。实验结果表明：气压是影响尖端、悬浮与沿面缺陷放电的关键参数,3种缺陷放电起始电压与气压成正比,同一电压下的放电幅值和脉冲次数与气压成反比;气隙缺陷放电源于绝缘层内部气泡,因此设备气压对气隙缺陷放电影响不大。高频电流法可实现不同气压下的悬浮缺陷有效检测,但未测得气隙和尖端缺陷局部放电信号;SF₆压力降低,高频电流对沿面缺陷的检测灵敏度有所提升,但仍低于特高频法。超声法可实现不同气压下的悬浮和尖端缺陷有效检测,但未测得气隙和沿面缺陷局部放电信号;SF₆压力降低,超声法对尖端缺陷的检测灵敏度提高(当气压为0.2 MPa时,超声法对尖端缺陷的检测灵敏度与特高频法相当)。     

基于QEPAS检测氨气痕量气体的研究

痕量氨气(NH_3)检测在大气质量监测和人类疾病预防等方面具有重要意义,然而现有氨气检测方法难以满足当前需求。针对石英增强型光声光谱技术(quartz enhanced photoacoustic spectroscopy,QEPAS)具有灵敏度高、监测实时性好、环境噪声免疫性高等优点,该文在阐述检测原理的基础上,选用中心波长为1531.65 nm的分布反馈式激光器(distributed feedback laser,DFB)作为光源,室温下氨气标准气体作为被测对象,搭建了基于QEPAS的NH_3气体检测系统。该系统确定了谐振管的尺寸和位置,优化了激光滤波准直光路,并结合波长调制与谐波检测技术,实现了氨气浓度的检测。检测结果表明,QEPAS系统的二次谐波信号与NH_3浓度具有良好的线性关系。该系统的检测极限精确度为146 ppb,稳定响应时间约为40 s,4小时连续检测相对误差为2.34%。     

Laser sensor for detection of SF6 leaks in high powerinsulated switchgear systems

A novel photoacoustic spectrometer (PA) has been developed for in-situ detection of SF₆ leaks in low concentrations. The developed system is equipped with a sound alarm system and has been tested in the laboratory for very minute SF₆ leaks. This newly developed SF₆ detection device utilizes a high quality factor resonant photoacoustic cell and continuous wave (CW) line tunable CO₂ laser at 10.55 μm wavelength. Whenever SF₆ is detected an acoustic signal is generated and no signal appears from ambient air if there is no leakage of SF₆. An electret microphone is used for the detection of these acoustic signals. The system is capable of detecting leaks of the order of 3.5 ppbv (parts per billion by volume) concentration. This device has been proved to have significant applications to industrial organizations that have electric power gas insulated systems (GIS). It could be also applied for other applications such as monitoring of environmental pollutants with minimal adjustments     

Modelling of chemical surface acoustic wave sensors and comparative analysis of new sensing materials

Comparative analysis of different, new gas sensing materials in surface acoustic wave chemical sensors is presented. Different gas sensing materials as polyaniline (PANI), Teflon AF 2400, polyisobutylene (PIB), polyepichlorohydrin (PECH) are considered. They are chosen according to the type of gas to be detected and the desired accuracy: Teflon AF 2400 thin film for the detection of CO₂, PANI nanocomposites film that belongs to the group of conductive polymers for the detection of CO, NO₂ and phosgene (COCl₂), and PECH and PIB for the detection of dichloromethane (CH₂Cl₂, DCM). In the analysis, the simple and useful method of the complete analyses of gas chemical sensors is used. The method is based on the electrical equivalent circuit of the surface acoustic wave sensor. The method is very efficient and can be used for the optimal design of CO₂ sensors. The results are compared with those presented in public literature and good agreement is obtained, demonstrating the validity of modelling. Copyright © 2012 John Wiley & Sons, Ltd.     

可调谐半导体激光吸收光谱甲烷浓度监测系统

以中心波长为1 650 nm的激光光源作为探测光源,并结合波长调制光谱以及谐波探测技术,设计了一套基于TDLAS(可调谐二极管激光吸收光谱)技术的CH4气体浓度探测系统.结合长光程测量池,以浓度为99.999%的高纯N2为背景气体,对8种浓度的CH4气体进行了测量,利用配置的101×10-6 CH4气体对系统进行了稳定...     

Development of switching principles and phase comparison techniques for distance protective schemes

The paper represents further work on phase comparison techniques by the same author. Two techniques are reported here. The first one describes a new principle of operation employed for the main functions of starting elements for fault detection and selection of phase(s). The principle is based on a process of phase comparison accomplished between comparison quantities derived from the three symmetrical components of line current relative to only one phase of the protected line section. Fault detection and phase selection are achieved by delivering nine distinct orders from the starting element corresponding to the nine cases of asymmetrical faults. The starting element based on this principle reduces the switching time to 3.33 ms.The second technique is concerned with phase comparison techniques to improve the security and reliability of the high-speed comparator described previously by the same author. The modus operandi consists of continuously monitoring the coincidence of compared comparison periods derived from the two relaying signals and simultaneously the non-coincidence of another set of compared comparison periods derived from the same relaying signals. Fault detection is achieved by delivering a trigger output from the comparator corresponding to non-coincidence of the first set and coincidence of the second set of comparison periods.     

Insulation properties of a CO2/N2 50% SF6 gas mixture in a nonuniform field

This paper describes partial discharge (PD) inception and breakdown voltage characteristics of a CO₂/N₂/SF₆ gas mixture in a nonuniform field. These voltage characteristics were investigated with ac high voltage by changing the mixture rate of each gas of CO₂, N₂, and SF₆ gas and the gas pressure from 0.1 MPa to 0.6 MPa. It was found that adding a small amount of CO₂ gas into a N₂/SF₆ mixture causes a drastic increase in the breakdown voltage. For instance, when the mixture rate of SF₆ in N₂/SF₆ gas mixture is 50%, with the addition of 1% CO₂ the maximum breakdown voltage becomes 1.31 and 1.15 times higher than that of a 50% N₂/50% SF₆ gas mixture and pure SF₆ gas, respectively. Moreover, those voltage characteristics of a CO₂/N₂/SF₆ gas mixture were also investigated by changing the electric field utilization factor as well as by applying positive and negative standard lightning impulse voltages in order to discuss the corona stabilization effect, which seems to be one reason for the drastic increase in the breakdown voltage. These results and breakdown mechanism of the CO₂/N₂/SF₆ gas mixture are discussed on the basis of the corona stabilization effect and the dissociation energies of the component gases by observing PD light images, PD light intensities through a blue and red filter, and PD current waveforms. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 140(3): 34–43, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10019