Novel Fiber Optic Current Transformer With New Phase Modulation Method

Based on the transverse electro-optic effect of lithium niobate crystal,combined with polarizers and Faraday rotator,this paper presents a collinear closed-loop fiber optic current transformer with spatial non-reciprocity modulation method,and the feasibility of the scheme is verified by both the theoretical and experimental evidences.The detection scheme avoids the limitation of the transition time of the sensing fiber coil on the phase modulation frequency,improves the sensitivity and stability of the system,and reduces the volume and cost of fiber optic current transformer.The sawtooth wave modulation scheme is adopted to realize phase bias modulation and feedback modulation through phase shift of sawtooth wave to achieve closed-loop detection effect,which enhances the signal to noise ratio and simplifies demodulation mode.The experimental results show that the current ratio errors measured at room temperature range from 1%to 120%of rated current meet the requirements of national standard GB/T 20840.8-2007 and reach the accuracy level of 0.2S.The temperature stability of the current transformer is also tested,and the ratio error measured at the rated current does not exceed±0.2%in the range of-30℃to 50℃.

Signal processing for all fiber optical current transducer

The work principle of all fiber optical current transducer (AFOCT) was introduced. By analyzing the characteristic of photo-detector's output, a measurement and signal processing scheme based on sine wave modulation and demodulation was put forward for eliminating the influence of light intensity change and modulation degree change. A digital signal processing system and a calibration scheme were also advanced. The experimental data show that the mean ratio error is 0.016 74% for direct current and 0.035% for alternating current, and the correlation coefficient of linearity is up to 0.999 982 4, meeting the precision requirement of 0.2 grade. Stability experiments and temperature drift experiments show the AFOCT has a better stable capability.

Effect of Modulation Error on All Optical Fiber Current Transformers

For actively modulated In-line Sagnac interferential all optic fiber current transformers (AOFCTs), the accuracies are directly affected by the amplitude of the modulation signal. In order to deeply undertand the function of the modulator, a theoretical model of modulation effect to AOFCTs is built up in this paper. The effect of the amplitude of the modulation signal to the output intensity of AOFCTs is theoretically formulated and numerical calculated. The results show that the modulation voltage variation could affect the output accuracies significantly. This might be some references on the investigation for practical applications of AOFCTs.

Design and applicability analysis of independent double acquisition circuit of all-fiber optical current transformer

The advantages of the all-fiber optical current transformer include but are not limited to being small in size,having no magnetic saturation,exhibiting high measurement accuracy,and boasting strong electromagnetic interference resistance.However,the high cost of the all-fiber optical transformer limits its promotion and application in engineering.This paper proposes a design scheme of an independent double acquisition loop for the all-fiber optical current transformer based on the single optical path.Firstly,based on the closed-loop control mode and open-loop control mode,the twochannel sampling signal demand for relay protection,and the independent dual-acquisition loop design scheme of the all-fiber optical current transformer are proposed.Secondly,the reliability and economic feasibility of the scheme are demonstrated by an analysis of system failure and cost.The results show that the scheme can actualize the acquisition function of two independent all-fiber optical current transformer products on a single all-fiber current transformer in an integrated manner,which greatly reduces the cost of the all-fiber optical current transformer in engineering applications.

A Passive Optical Fiber Current Sensor Based on YIG

A research on passive optical fiber current sensor based on magneto-optical crystal and a new design of light path of the sensor head are presented. Both methods of dual-channel optical detection of the polarization state of the output light and signal processing are proposed. Signal processing can obtain the linear output of the current measurement of the wire more conveniently. Theoretical analysis on the magnetooptical fiber current sensor is given, followed by experiments. After that, further analysis is made according to the results, which leads to clarifying the exiting problems and their placements.

Feasibility and Application Study of Optical Voltage/Current Sensors Using FBG

This paper concludes the case study work on the optical sensor, which is a new method for voltage and current measurement. Fiber Bragg gratings (FBG) have been developed and used for decades in the telecommunication industry. In recent years, FBG sensors have found wide applications in monitoring strain, temperature, voltage and current across all industries. As the process of constructing a robust smart grid, thousands of miles of optical-fibers have been deployed along the power transmission lines for the purpose of power production communication. This paper focuses on using the power optical fiber as voltage/current sensors instead of those copper wired traditional current transformers. By using piezoelectric layers, the optical sensor is able to transform voltage/current magnitude into optical signal, as well as transmit the signal through the optical fiber. The application of using optical fiber will significantly reduce the cost of deploying traditional current transformers all around the power grid. Moreover, the optical sensor is more stable, more accurate and faster, with such characteristics, the smart grid monitoring system could be much better. The application of combining the optical composite low-voltage cable (OPLC) and the optical current sensor in the distribution network for smart distribution monitoring has been analyzed.

塑壳断路器可靠性试验电源的光纤校准技术研究

针对塑壳断路器可靠性试验电流的大幅值、短时、交直流混合等特点以及现场复杂工况对大电流标准传感器的严苛要求,提出了基于光纤电流传感技术的塑壳断路器可靠性试验电源现场校准方法。根据光纤电流传感器的闭环检测原理建立了系统的动态模型,分析了阶跃响应和频率响应特性,仿真结果表明:通过调节系统的前向增益及滑动滤波器阶数,传感器的上升时间优于9.09μs,-3 dB带宽可达39.91 kHz,证明了光纤电流传感器对塑壳断路器可靠性试验电流的跟踪响应能力。基于等安匝法对光纤电流传感器进行校准,评定了校准结果的不确定度,结果表明:在2.5~60 kA范围内,传感器的直流、工频电流测量准确度优于0.2%。对塑壳断路器可靠性试验电流进行了现场测试,为塑壳断路器可靠性试验电源的现场校准提供了一条技术途径。

残余线双折射对于全光电流互感器工作点稳定性的影响

保椭圆光纤中残余线双折射易受环境影响,导致光纤电流互感器(FOCT)性能易受环境影响。利用四元数方法,理论分析了因残余线双折射的存在,将导致全光纤电流互感器的工作点不稳定问题。结果表明,保椭圆光纤的圆双折射与残余线双折射之比RCL(圆/线比)的大小直接影响工作点的稳定性,总的趋势是随着RCL的增加,工作点越稳定。当RCL<2时,工作点极不稳定;当RCL>4后变得相对稳定。因此,参数RCL是一个衡量保椭圆光纤的重要指标,应在制作全光电流互感器前进行测定,确保FOCT的性能。

海流探测仪器与技术研究现状及展望

精准、实时的海流数据是海洋资源开发与利用、海洋科学研究等方面的重要输入参数之一。海流探测仪器按照测量原理主要分为机械式、电磁式、声学多普勒式和声学时差式4类传统海流计,以及当前结合了光纤传感等技术的新型海流计。在本文中,作者从探测原理、优缺点、应用领域、发展现状等方面对传统海流计与光纤类海流计进行了梳理与总结,展望了未来海流探测仪器的发展趋势,并提出了一种基于连续时差法的光致超声测流方法。旨在对海流计的开发与研究提供借鉴与参考,在增进海洋探测技术的发展、加快实施海洋强国战略中具有一定的意义。

光电复合缆载流量监测系统光电子器件可靠性分析

针对构成光电复合缆载流量监测系统的分布式光纤温度传感器(DTS)和全光纤电流互感器(FOCT)的运行可靠性问题,基于可靠性框图法,对其中的关键光电子器件及信号处理模块建立可靠度、失效率和平均寿命分析模型,仿真分析了使用环境、运行时间和管芯温度对系统可靠性的影响。结果表明,DTS和FOCT系统中关键光电子器件的失效率均随管芯温度的增加而增加,可靠度随管芯温度和使用时间的增加而降低,平均寿命随管芯温度的增加而降低,且使用环境越恶劣,整体可靠性越低,在光源管芯温度为50℃,运行时间为31500 h,使用环境良好的条件下,DTS和FOCT系统的失效率、平均寿命及可靠度估计值分别为9.84×10^(-5)1/h、10160.96 h、0.2342和1.026×10^(-5)1/h、97434.947 h、0.65316。

AFOCT系统中敏感光纤器件的老化对系统测量准确性的影响

研究了全光纤电流互感器(AFOCT)系统中敏感光纤器件老化对系统测量准确性的影响。首先,基于法拉第磁光效应,采用琼斯矩阵建立AFOCT系统的传输模型;结合存在双折射的传感光纤的琼斯矩阵,给出系统的注入电流测量值的表达式。进一步,搭建了光学测试系统,实验表征传感光纤的双折射率;基于测试结果,对传感光纤的琼斯矩阵以及系统传输模型进行校准,以降低AFOCT系统注入电流的测量误差。最后,对传感光纤开展了相当于实际运行3个月的加速老化试验,并测试获得老化后传感光纤的双折射率。采用校准后的AFOCT系统传输模型,分析了老化后双折射率的变化对系统注入电流测量值的影响。实验结果表明,在传感光纤老化3个月之后,系统就已经产生了0.2955%的相对误差。

柔性直流光纤电流互感器阶跃响应特性研究

传统直流光纤电流互感器无法满足柔性直流输电工程的高速响应需求,因此需要研究直流光纤电流互感器的阶跃响应特性及其动态性能改善方法。文中结合直流光纤电流互感器的离散数学模型,对其动态特性进行了全面的仿真、计算和实验研究,结果表明:影响直流光纤电流互感器阶跃响应特性的关键参数是渡越时间、前向通道增益、滤波器阶数和通讯延迟。搭建了直流光纤电流互感器阶跃响应测试平台,经参数优化后的直流光纤电流互感器的阶跃响应上升时间小于50μs,满足相关应用要求。

煤矿供配电系统中防越级跳闸保护技术

本文旨在研究煤矿防越级跳闸保护技术的选取和应用。根据项目背景,通过四种防越级跳闸保护技术选取方案对比,最终确定采用纤电流纵差保护方法,并对该方法的具体技术应用进行详细论述,最后进行了防越级跳闸保护实验,以验证所选取的防越级跳闸保护技术的有效性,研究结果为煤矿防越级跳闸保护提供了理论依据和实践指导。

直流大电流综合试验装置校准方法探讨及不确定度解析

直流大电流综合特性试验装置是用于检测直流低压电器过流保护电器的脱扣动作特性的仪器,指在低压电器行业用于对直流产品进行长延时、短延时、瞬时脱扣试验和短路试验的测试设备。随着直流低压电器产品在有色冶金、氯碱化工、低压配电、直流输配电、新能源以及轨道交通等领域的广泛应用,用于直流电器产品检测的直流大电流综合特性试验装置需要定期溯源,以满足试验检测能力的准确度要求。在计量校准领域内展开相关校准方法的现状分析,梳理了现阶段此试验装置校准方法的研究方向。根据试验装置对应产品,依据国家标准,提出新的校准参数,针对直流大电流装置的校准问题,提出使用光纤电流传感器测量方法进行测量,并对其产生的数据进行不确定度评定分析。

闭环全光纤电流互感器阶跃响应上升时间研究

应用于柔性直流输电工程的闭环全光纤电流互感器(FOCT)为满足工程应用,需使用长距离保偏光缆实现偏振光信号的远距离传输,对其阶跃响应上升时间的影响尚未论证。此处从工作原理及输出特性两个方面分析了闭环FOCT采用M阶滑动平均滤波器特性、阶跃响应上升时间,并进行了仿真及试验验证,结果表明:影响阶跃响应上升时间的关键因素为光路渡越时间和滑动平均滤波器阶数,滤波器积分时间与闭环FOCT阶跃响应上升时间正相关;增加300m保偏光缆后闭环FOCT阶跃响应上升时间显著增加,通过控制滑动平均滤波器的积分时间可使闭环FOCT阶跃响应上升时间及测量性能与不增加长距离保偏光缆保持一致,解决了闭环FOCT增加保偏光缆引起阶跃响应上升时间增加的问题,满足柔性直流输电工程对其快速响应及特性稳定的需求。

大容量试验系统中光纤电流互感器的研究

在高压大容量检测系统中,电流测量系统作为重要的组成部分,用于对开关、熔断器等电气设备进行高压大电流试验时的瞬态数据测量,以及开断能力、抗短路能力等关键指标的测试。传统高压大容量检测系统中电流测量所使用的电流分流器、电磁式电流互感器、罗氏线圈、霍尔传感器等有着各自的应用局限性,对测量系统的精确度、抗干扰、稳定性等对测量结果有直接影响。分析了当前高压大容量测试系统中不同类型电流采集系统的优缺点,对应用于当前系统中的光纤电流互感器的研究过程进行了简要概括,并通过在系统中实际引入光纤电流互感器产品与传统测量方式进行了比较,验证了产品应用于高压大容量检测系统的可行性。

主变压器长距离保护方案的研究

文章在主变压器、各侧一次设备与二次设备的布置存在长距离的特殊场景下,对主变压器保护进行了探讨。从电流互感器的选择及计算入手,结合线路光纤电流差动保护的二次接线特点等方面,对主变压器长距离保护进行了全面分析。主变压器长距离保护方案的快速保护、后备保护以及保护范围,均可替代典型方案,而且对电流互感器的选择不会提出少见的参数需求。对市面上成熟的保护设备进行灵活组合,调整电流互感器二次绕组和保护装置的二次接线,可有效解决长距离特殊场景下的主变压器保护配置问题。

基于单元系统的光纤通信网络安全保护方法设计与验证

为提高和保障单元系统通信网络安全,针对多项阈值影响下的网络运行状态差异较大,导致强电保护效果较差问题。设计了光纤通信网络安全与强电保护方法。根据建筑单位系统光纤通信网络特性,分析光纤材料风险性质,计算对应的风险评估值,从防火墙设计、数据加密和备份等多个模块入手,设计光纤通信网络强电保护机制;计算光纤通信网络运行中的多项阈值,对比实际情况,判断光纤通信网络运行状态,更新强电保护机制。实验结果表明,该方法应用后,安全性概率数值保持在95%左右,强电保护机制平均运行开销为1.30。安全性概率较高,运行开销较小,强电保护效果较好。

光纤资源管理在科技园智能楼宇弱电工程中的应用

以提升智慧科技园区的整体效能为主要目标,文章深入研究了光纤资源管理在科技园智能楼宇弱电工程中的应用,并将智慧城市、智慧科技园区和智能楼宇电气工程作为背景,特别关注了楼宇5G手机信号覆盖、楼宇综合布线和光纤资源智能管理等关键要素。在此基础上,提出了光纤资源智能管理的关键技术,包括光纤网络监测与诊断、光纤资源调度与优化、安全性与隐私保护等。其中,首先对智慧城市和智慧科技园区进行了简要介绍,强调了智能楼宇电气工程在科技园区建设中的核心地位;其次深入讨论了楼宇5G手机信号覆盖、楼宇综合布线和光纤资源智能管理的重要性;最后围绕关键技术详细探讨了光纤网络监测与诊断、光纤资源调度与优化、安全性与隐私保护等,所提关键技术不仅能实时监测光纤网络状态,还能诊断潜在问题。

Stochastic noise identification in a stray current sensor

The Allan variance analysis method is used to identify the stochastic noise in the stray current sensor. The stray current characteristic is firstly introduced. Then the optical configuration and the signal processing method of the stray current sensor are illustrated. Moreover, the cause of the stochastic noise in the stray current sensor is analyzed. The calculation method of the stochastic noise coefficient is presented in detail. And the feasibility of the stochastic noise identification with the Allan variance analysis method is evaluated. Furthermore, the zero-drift signal acquisition experiment is conducted to identify the stochastic noise in the stray current sensor. According to the experimental result, the bias instability noise, the quantization noise and the white noise are identified as the major stochastic noise. Finally, the experiment on the direct-current signal acquisitions is conducted, whose results indicate that the signal drift of the measured direct-current is mainly caused by the major stochastic noise. And the suppression methods of the major stochastic noise are proposed.