Magnetoresistive (MR) sensors have been identified as promising candidates for the development of high-performance magnetometers due to their high sensitivity, low cost, low power consumption, and small size. The rapid advance of MR sensor technology has opened up a variety of MR sensor applications. These applications are in different areas that require MR sensors with different properties. Future MR sensor development in each of these areas requires an overview and a strategic guide. An MR sensor roadmap (non-recording applications) was therefore developed and made public by the Technical Committee of the IEEE Magnetics Society with the aim to provide an research and development (R&D) guide for MR sensors intended to be used by industry, government, and academia. The roadmap was developed over a three-year period and coordinated by an international effort of 22 taskforce members from ten countries and 17 organizations, including universities, research institutes, and sensor companies. In this paper, the current status of MR sensors for non-recording applications was identified by analyzing the patent and publication statistics. As a result, timescales for MR sensor development were established and critical milestones for sensor parameters were extracted in order to gain insight into potential MR sensor applications (non-recording). Five application areas were identified, and five MR sensor roadmaps were established. These include biomedical applications, flexible electronics, position sensing and human-computer interactions, non-destructive evaluation and monitoring, and navigation and transportation. Each roadmap was analyzed using a logistic growth model, and new opportunities were predicted based on the extrapolated curve, forecast milestones, and professional judgment of the taskforce members. This paper provides a framework for MR sensor technology (non-recording applications) to be used for public and private R&D planning, in order to provide guidance into likely MR sensor applications, products, and services expected in the next 15 years and beyond.

Smart living is a trending and connected lifestyle that envisions efficient and sustainable energy utilization, stable and reliable power supply, intelligent and coordinated transportation and mobility, and personalized and cost-effective healthcare. Its realization needs the Internet of Things (IoT). IoT is a compelling platform connecting trillions of sensors and collecting data for connectivity and analytics. It is more advanced than traditional monitoring systems where limited sensors and wired communication can merely collect fragmented data in the application domains. Spintronic sensors with the superb measuring ability and multiple unique advantages can be one of the critical sensing devices supporting the IoT and enabling smart living. In this paper, we review successful applications of individual spintronic sensors in electrical current sensing, transmission and distribution lines monitoring, vehicle detection, and biodetection that can help to fulfill the promises of smart living in energy management, power delivery, transport, and healthcare. The wireless spintronic sensor networks (WSSNs) working at the massive interconnected network level are proposed and illustrated to provide pervasive monitoring systems, which facilitate the intelligent surveillance and management over building, power grid, transport, and healthcare. The database of collected information will be of great use to policy making in public services and city planning. This paper provides insights for realizing smart living through the integration of IoT with spintronic sensor technology.

Adopting non-contact capacitive coupling for voltage monitoring is promising as it avoids electrical connection with high-voltage transmission lines. However, coupled voltage transformation matrix to correlate voltage of overhead transmission lines and induction bars has not been achieved mathematically due to the lack of equivalent electric circuit model for analyzing the physical phenomenon. Moreover, exact spatial positions of overhead transmission lines are typically unknown and dynamic in practice. In this paper, a technique based on non-contact capacitive-coupling and assisted by magnetic-field sensing for monitoring voltage of overhead transmission lines was designed and implemented. The technique in this paper is demonstrated on a single-circuit transmission line as an example, while it is also applicable for multi-circuit transmission lines. The capacitive coupling between overhead transmission lines and induction bars were modeled as lumped capacitors, and then, the equivalent electric circuit model was established. The coupled voltage transformation matrix to correlate voltage of overhead transmission lines and induced voltage of induction bars mathematically was formed accordingly. This paper was also carried out to analyze the effect of ground wires, sensitivity of induction bars, the ability of high-frequency transient measurement, and the intrinsic capacitance of a measurement instrument. The exact spatial positions of overhead transmission lines were acquired by integrating magnetic-field sensing with the stochastic optimization algorithm. The methodology was verified by simulation on the 10-kV single-circuit three-phase overhead transmission lines taking non-ideality of signal measurement in account, and wavelet de-noising algorithm was supplemented to filter the interferences. A scaled testbed to experiment the technique was built to monitor 220 V overhead transmission lines in the lab, and also the typical waveform of a high-frequency switching surge (up to 1 kHz), which was generated by a programmable ac source. The reconstructed results match well with the actual values. This technique can largely improve transient-fault identification over traditional potential transformers by the virtue of the increased upper measurement limit and bandwidth through capacitive coupling. Moreover, it can be implemented with low-cost copper induction bars and compact magnetoresistive sensors, enabling large-scale application to realize sectional monitoring in the wide area.

Current monitoring can facilitate preemptive action in electrical distribution network, so as to relieve power congestion, improve transmission efficiency, and ensure network reliability. The non-invasive current sensing devices are promising since they do not require contacting hazardous high voltage and their installation is much easier compared with invasive current sensing devices. However, the existing non-invasive current sensing devices, such as current clamps and Rogowski coils are only applicable for measuring single-core underground power cables. In this paper, we established a non-invasive technique, that can monitor the currents of a multi-core underground power cable by measuring the emitted magnetic field around the cable surface. The additional magnetic fields generated by induced and leakage currents on the cables were firstly evaluated. Magnetoresistive (MR) sensors in a circular array were adopted to measure magnetic field around the cable surface, and a triple-layer shielding was designed to reduce the effects of external interference. Regarding intrinsic noise in MR sensors (e.g., 1/f noise and thermal noise), magnetic flux concentrators were supplemented to improve the signal-to-noise ratio. The developed platform was tested in a substation, and the reconstructed results closely matched the real geometrical configuration and current records of the tested cable. Apart from the non-invasive feature, the platform also shows great potential to improve the sensing capability of current amplitude and frequency compared with CTs by adopting MR sensors.

Noncontact monitoring technique of mechanical and electrical states is increasingly attractive for the overhead transmission system. This paper proposes a new technique to detect the tower inclination and transmission line sag, and measure transmission current simultaneously. The key of this technique is to use the ground magnetoresistive (MR) sensor to measure the magnetic flux density along the center line from the three-phase transmission lines. Moreover, the magnetic field (MF) calculation formulas for a tilted tower are given in this paper. Finally, with MF calculation formulas, an algorithm based on artificial immune system (AIS) is applied to estimate the transmission line sag and tower tilt angles, and reconstruct currents. Model simulations of an overhead transmission system are carried out to verify the idea. The simulation results validate the feasibility of this noncontact approach to estimate mechanical parameters and reconstruct electrical parameters for overhead transmission system.