应用光纤Bragg光栅的新型直流电流测量方法

New Method for Direct Current Measurement by Using Fiber Bragg Grating

光学电流互感器因具有许多传统电磁感应式电流互感器无法比拟的优点,具有广阔的应用前景,但目前国内应用于直流测量的研究报道较少。为此基于光纤Bragg光栅的应变敏感性和磁性材料的磁致伸缩效应,提出了一种新型直流电流测量方法。在详细分析超磁致伸缩材料(GMM)调制光纤光栅时存在的磁滞非线性以及测量精度的温漂问题后,通过施加合适的偏置磁场、预压应力,改善了磁滞非线性特性,利用光纤Bragg光栅的可串联特性设计温度补偿系统,解决了温漂问题,实现了光纤Bragg光栅(FBG)波长漂移量与轴向应变量的线性调谐关系,并以此设计了实验样机。实验表明,该装置具有结构简单、线性度好、灵敏度高等特点。该方法为高压直流输电电流检测提供了一种新的有效手段。

Optical current transducer used to measure the current of power system is superior to electromagnet-induced current transducer in many aspects. In this paper, based on the susceptibility of fiber Bragg grating （FBG） to strain and the magnetostriction effect of magnetic materials, a new method for direct current measurement is proposed. The problems, such as magnetic hysteresis, nonlinearity and wavelength shift induced by temperature, which occur while the fiber Bragg grating is modulated by giant magnetostrictive materials （GMM）, are analyzed in detail. The nonlinearity characteristic of giant magnetostrictive materials is inhibited effectively by using optimal design of the sensor head structure and adding proper bias magnetic field and pre-stressing force, and the magnetic hysteresis of magnetostrictive material is reduced as well, therefore, the linear tuning relationship between fiber Bragg grating wavelength shifts and the giant magnetostrictive materials axial strain variable can be achieved. The temperature compensation system is designed by using the series characteristic of fiber Bragg grating to solve shift problem induced by temperature while the fiber Bragg grating is modulated by giant magnetostrictive materials, which makes the repeatable metering of current possible. According to this method, an experimental device is designed, and the test results demonstrate that this device has characteristics of simple structure, good linearity, and high sensitivity. The method provides a new effective way to measure the current of high-voltage direct-current transmission.