Abstract:With the accelerated construction of the new power system and the continual improvement of intelligent power equipment, low-carbon and digital construction of electric power equipment have become an important trend. Among them, the accurate measurement of the magnetic field distribution of electrical equipment in power systems is the key of its health status evaluation, energy losses calculation and structural design optimization. A passive optical fiber magnetic field sensor was designed in this paper to meet the measurement requirements of the magnetic field generated from the electrical equipment and to solve the bottleneck problems of the environmentally friendly power equipment. This sensor realized the high-precision passive measurement of the external magnetic field, which was based on the coupling structure between the magnetic-mechanical conversion functional dielectric and fabry-perot (F-P) optical interference cavity. First of all, the extrinsic F-P interference structure was designed according to the F-P interference principle. Besides, the influence of different packaging materials on the sensitivity of the sensor was discussed by measuring the magnetic sensing properties of sensors with various materials. The sensing performance of the sensor under DC magnetic field was tested, and influence factors of the measurement range was studied to obtain a wide measurement range. Finally, the dynamic performance of the sensor was tested under the AC magnetic field according to the measurement requirements in the power system. The results showed that this sensor can realize real-time detections of the AC/DC magnetic field. The measurement range, sensitivity and resolution of the sensor were 0～120 mT, 447 pm/mT and 17 μT respectively. Meanwhile, it had excellent tracking properties for the AC magnetic field below 50 Hz, which proved the feasibility for its application in the passive magnetic field measurement of the new power system. Hence, the optical fiber magnetic field sensor proposed in this paper has the advantages of a wide measurement range and passive measurement characteristics, without the need of the battery replacement or the power supply from the induction, which meets the development requirements of low carbon power systems.