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.

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.

Optically Driven Current Transformer with Optical Fiber Data Link

An optical fiber transmitting photoelectric coupling current transformer has been developed. In the environment of high voltage and electromagnetic fields, this device is characterized by high insulation, high reliability, small mass and high anti-interference. The structure design and operating principle of the system are introduced, measurement errors are analyzed and experimental results are given.

Optical fiber-based power and data delivery system for high voltage electronic current transformer

This paper describes a prototype power delivery system developed for high voltage electronic current transformer （ECT） that uses laser light to transfer power to and communicates with the primary converter. The design is based on optical-to-electrical power converters, solid-state diode lasers and optical fibers. Command signals are transmitted via the same up-fiber used to send power from secondary power supply to primary converter. The upward data transmission is completed during the brief interruption of power delivery without affecting steady power-supply. A simple comparator added to the primary converter can take the command data. Experimental results show that the fibers can provide reliable up-link for data transmission at 200 kb/s from the secondary to the primary converter. Based on the delivery system, the secondary converter can control three auxiliary channels to provide additional information. These monitoring channels are used in a time-multiplexing mode to provide information about the operation temperature, voltage and current at the remote unit for monitoring the ECT. This preventive maintenance or built-in test can increase reliability by giving early warning for necessary maintenance request.

Optical Design of OCT with Gapped Magnetic Ring

The mathematics and physics model of OCT (Optical Current Transformer) with a gapped magnetic ring is briefly discussed in the paper. And some proposals of how to select the magnetic materials and crystals and reduce the stress birefringence of the crystal are also put forward in the paper. Based on the above, an OCT with 1000 A rated current is designed by using the ANSOFT Maxwell tools.

Novel Perturbation-Immune All-Fiber Optical Architecture for Current Sensing

This paper describes a novel all-fiber optical architecture for electric current or magnetic field sensing which is immune against temperature and vibration perturbations in a hazardous environment. The architecture is structured by employing the fiber-optic wave plates (quarter, half or full) of the patented invention of the senior author. Experimental results on prototype fiber-optic specimen and on a variety of optical fiber networks confirm the respective theoretical predictions.

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。

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。

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。

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。

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℃.

基于马赫-曾德干涉仪的光纤电流互感器设计

电流互感器作为一次侧电流的常用计量设备之一,它在电力系统的交流电测量、继电保护、电力设备检修控制等相关领域均具有十分重要的地位。针对传统电流互感器存在的线性度低、抗干扰能力差及精度低等问题,尤其在工频小电流精确测量这一难题方面更是捉襟见肘。鉴于此,本文提出一种基于马赫-曾德干涉仪的光纤电流互感器。该互感器利用电流经过电阻所产生的焦耳热改变光纤中的光信号特征,从而引起马赫-曾德干涉仪的输出信号变化,然后通过光电探测器完成对干涉仪的光信号捕捉,并将其转换为电信号输出,完成工频小电流检测。结构上通过采用PCB型罗氏线圈作为感应取电装置,并利用MATLAB完成其动态响应分析。另外针对信号采集、传输、处理过程中所出现的噪声信号,设计了基于FPGA技术的信号处理系统,以提高信噪比。最后通过实验对工频小电流进行测量,线性度为0.9961,检测精度可达到0.14%。实验结果表明提出的光纤电流互感器相较于传统光学电流互感器相比,具有更高的线性度和测量精度,为基于热效应的电流互感器发展提供了新的思路,也为工频小电流的测量提供了一种新的方法。

磁控光阀型闭环无源电流互感器性能研究

为实现电力系统电流信息的安全、精准、低成本测量,基于微光机电系统技术,提出一种磁控光阀型无源光学电流传感方案,其具有调制速率快、量产成本低等特点。并提出基于微功率光控信号源的闭环光反馈回路结构,以进一步提高系统的线性度和动态范围。且完成了样机研制,并依据GB/T 20840.8-2007规定的220 kV电子式电流互感器测试规范,对其准确度及线性度进行了测试。结果表明,该系统比差(RE)波动范围在60 A时为-0.3%~0.25%,在1440 A时为0.02%~0.05%,准确度满足计量0.2级的误差限值要求。

正弦波调制全光纤电流互感器光回路故障预警方法

正弦波调制全光纤电流互感器(fiber optical current transformer,FOCT)因具备动态范围大、不与一次主回路连接、绝缘性能好、无铁磁饱和等优点,成为特高压换流站重要的测量设备。但在实际运行过程中,FOCT故障率远高于电磁互感器,而光回路故障是最为常见的故障类型。针对此,首先建立FOCT数学模型,提出二次谐波、光强峰值、平均光强应作为重要监测量;在此基础上分析光回路故障对探测器输出信号的影响,提出基于驱动电流及探测器输出信号变化的光回路故障预警方法,通过阈值设置及平均光强趋势判断等辨识真实的光回路故障。最后开展现场试验验证,证明该预警方法的有效性。

正弦波调制FOCT调制回路故障对探测器输出特性影响

为探究全光纤电流互感器(fiber optical current transformer,FOCT)调制回路故障对探测器输出信号影响,便于故障预测与故障诊断,文中首先建立包含光电回路相位延迟的正弦波调制FOCT输出信号数学模型,给出调制深度与驱动电压、二次谐波、四次谐波的数学关系式,分析定目标值调制器闭环调制、解调的基本方法。在此基础上通过建立数学模型分析调制深度对探测器输出光强峰值、平均光强、二次谐波、四次谐波的影响。据此提出发生调制回路故障时调制深度降低是导致探测器输出信号异常的关键因素,探测器输出平均光强增大、四次谐波降低、二次/四次谐波比值增加应作为调制回路故障的典型特征。最后开展实际FOCT模拟试验证明理论研究的有效性。

基于GOOSE协议的光纤电流互感器内部状态监测系统

光纤电流互感器中核心组件的运行状态直接影响测量结果的准确性和可靠性,针对其核心组件的状态信息进行监测具有重要意义。在智能变电站通信系统中,面向通用对象的变电站事件(GOOSE)信息流适用于监测数据量不大的设备,具有高实时性和可传递内部信息量的优点,文章基于GOOSE信息流设计和实现了监测光纤电流互感器内部状态的信息化系统。系统利用GOOSE收发机制传送与接收状态量,依据状态量特征解析Windows数据包捕获器获取的信息流,采用虚拟用户环境(Vue)框架的互联网前端开发技术设计交互界面,进行前后端联调,能够实时获取、整合、分析和处理光纤电流互感器内部的状态信息量。此外,该系统还能够将处理后的状态信息进行本地和远程动态展示,以实现信息的相互共享和操作的协同互通。综上,利用GOOSE信息流高效监控光纤电流互感器状态信息,使其运行更加可靠,测量更加准确,为智能电网的发展提供有力支撑。

便携式光纤电流互感器误差分析及补偿方法研究

针对电解铝行业现场测试环境复杂的问题,提出了用一种便携式光纤电流互感器结构来代替传统固定光纤电流互感器。分析了温度对波片延迟度的影响,采用了一种变速旋转光纤代替传统的波片来抑制温度的影响;根据传感环柔性安装过程所导致的光路不闭合问题以及导体偏心位置进行研究,设计出一种柔性安装传感环骨架代替传统光纤环,降低不均匀磁场所带来的影响。该光纤电流互感器在-20~70℃温度下输出比差小于0.2%,同时在100~3000 A的直流电流测试中满足0.2级的精度要求。

基于应力分析法的光学电流互感器信号适用性研究

以分析光学电流互感器信号在不同应用环境下的适用性为目的,提出基于应力分析法的光学电流互感器信号适用性研究。分析光学电流互感器工作原理,设计并制作互感器试件,设置线圈式电流互感器和磁式电流互感器为对比设备。检测并采集互感器信号,利用应力分析法分析信号的可靠性和使用寿命,并对采集的互感器信号进行适用性分析。光学电流互感器信号在不同应用环境下具有较高的适用性。

光电流互感器故障引发交流滤波器差动保护动作问题分析

随着光电流互感器(纯光CT)越来越多地应用于特高压直流输电工程,纯光CT故障率也逐渐升高。介绍了某换流站因纯光CT电子单元故障引发交流滤波器小组差动保护动作跳闸的问题,分析了故障原因,定位故障于电子单元内,同时对故障电子单元进行实验室验证,确认故障根本原因为光源连接线接触不良导致光源驱动电流异常,造成输出光功率波动,并提出了整改意见。