Optical fiber current sensors are widely used in the online monitoring of a new generation power system because of their high electrical insulation, wide dynamic range, and strong anti-electromagnetic interference ability. Current sensors, based on fiber Bragg grating (FBG) and giant magnetostrictive material, have the advantages of high reliability of FBG and high magnetostrictive coefficient of giant magnetostrictive material, which can meet the monitoring requirements of digital power systems. However, giant magnetostrictive materials are expensive, fragile, and difficult to mold, so giant magnetostrictive composite materials have replaced giant magnetostrictive materials as the sensitive elements of sensors. High sensitivity, high precision, wide working range, low response time, and low-cost optical fiber current sensors based on magnetostrictive composites have become a research hotspot. In this paper, the working principle of the sensor, the structure of the sensor, and the improvement of magnetostrictive composite materials are mainly discussed. At the same time, this paper points out improvements for the sensor.

Fiber optic current sensor based on magnetostrictive composite material is suitable for multiple industrial fields. Aiming at increasing the low sensitivity caused by conventional magnetostrictive composites, this work designed optimized magnet focusing structure of magnetostrictive composite material to develop high-performance fiber optic current sensor. The influence of magnetic focusing structures on the performance of current sensor was analyzed and validated through theoretical modeling and finite element-based simulation. Experimental tests were carried out to validate the superiority of proposed sensor compared with the existing sensors. Results show that section B in the magnetostrictive composite material leads to the difference in magnet field distribution, and the proposed sensor is more sensitive than the sensors with conventional structure. A repeatability error of 2.5%, a sensitivity of 0.16952 με/A, and a linearity of 2.2 % can be achieved by the proposed hourglass type sensor with low-cost and wide range between 0 and 900 A.

This paper presents the design, fabrication, and characterization of a compact current sensor based on magnetostrictive composites and resistance strain gauges. Firstly, we designed three kinds of current sensors with different structures, in which the shape of the giant magnetostrictive material (GMM) was cuboid, cylindrical, and semi-cylindrical. A set of finite element method (FEM) simulations were performed to qualitatively guide the design of three prototypes of the current sensor. It was determined that the most ideal shape of the GMM was semi-cylindrical. Secondly, Terfenol-D (TD) powder and epoxy resin were mixed to prepare magnetostrictive composites. In this paper, magnetostrictive composites with different particle size ranges and mass ratio were prepared and tested. The results show that the magnetostrictive composites had the best performance when the particle size range was 149–500 μm and the mass ratio of epoxy resin to TD powder was 1:5. Finally, this paper tested the performance of the sensor. The sensitivity, repeatability, and linear working range of the sensor reached 0.104 με/A, 2.51%, and 100–900 A respectively, when only 0.31 g of TD powder was employed. This means that current measurement with low cost, high sensitivity, and wide range was realized.

Stray current affects the safe operation of subway equipment. The stray current leakage point can be located by measuring the current of subway running track. A magnetostrictive current sensor with high sensitivity and a large linear range is proposed to monitor track current. The design of the sensor is qualitatively guided by a set of finite element method (FEM) simulations to improve the sensitivity of the sensor. However, when the sensitivity of the sensor increases, the linear range decreases. To solve this problem, a novel current sensor, to the best of our knowledge, which is composed of magnetostrictive composites, steel bars, and adjustable coils, is presented. The linear range of the sensor is expanded by adjusting the different DC bias magnetic fields generated by the adjustable coils. The results show that when the measured current is 0–500 A and 500–1000 A, the Terfenol-D (TD) mass is only 0.14 g, and the sensitivity of the sensor is 0.391 µɛ/A and 0.418 µɛ/A, respectively. The current measurement with low cost, high sensitivity, and larger linear working range is realized, which is suitable for monitoring stray current leakage points.