This paper focuses on the application of digital twins in the field of electric motor fault diagnosis. Firstly, it explains the origin, concept, key technology and application areas of digital twins, compares and analyzes the advantages and disadvantages of digital twin technology and traditional methods in the application of electric motor fault diagnosis, discusses in depth the key technology of digital twins in electric motor fault diagnosis, including data acquisition and processing, digital modeling, data analysis and mining, visualization technology, etc., and enumerates digital twin application examples in the fields of induction motors, permanent magnet synchronous motors, wind turbines and other motor fields. A concept of multi-phase synchronous generator fault diagnosis based on digital twins is given, and challenges and future development directions are discussed.

In stationary power generation units such as distributed remote site power systems and ship power systems, diesel engine generator systems are essential for supplying electricity. This paper proposes a digital twin diesel generator system for teaching and research purposes. A five-layer resilient architecture, including a web interface layer, server cluster layer, real-time data layer, controller layer, and equipment layer, is proposed in this paper. Based on the resilient architecture, users are able to build, implement and monitor the digital twin through web interfaces. Apart from MATLAB/Simulink, a modeling tool called M2PLink is developed to allow users to create mathematical models using a block diagram editor similar to Simulink. Various basic blocks for control systems are provided for users to form sophisticated models. These models are converted into executable codes which are downloaded to the simulator in the controller layer, where the real-time simulations are implemented. A web-based real-time monitoring interface with many widgets such as charts, oscilloscopes, and three-dimensional (3D) animation is also provided for users to customize their monitoring interface. All the signals can be traced and all the parameters can be tuned in the monitoring interface. The users are able to interact with the digital twin just like they do with the real system. The proposed system can not only be used for research such as digital twin-assisted real-time online monitoring but also for educational purposes, which is not only cost-effective but can also ensure the safety of the user as well as the equipment.

Giant magnetoresistance (GMR) sensors have been widely used in current detection, compass, automobile, and Internet of Things. The linearity of GMR sensors relies on a magnetic annealing process above the blocking temperature of the antiferromagnetic layer, which causes the same magnetization directions in the free and pinned ferromagnetic layers. Here we construct an orthogonal magnetic anisotropic structure by using a relatively low annealing temperature of 145 °C, where the magnetization direction of the free layer is perpendicular to that of the pinned layer so that a linear output can be realized. Quantitative magneto-optical kerr microscope (MOKE) is used to investigate the vector distribution of the magnetic domains, showing that an orthogonal anisotropy is established by the low temperature annealing process. GMR magnetic field sensor with a sensitivity of 0.78 mV/V/Oe and a measurement range of −20 to 20 Oe is demonstrated, which provides an effective method to enhance the linearity of the magnetic sensors with spin valve structures.

As for the direct-current (DC) power systems, the DC leakage current sensor is indispensable for positioning insulation faults. And in this paper, a quasi-digital flux gate sensor was designed based on duty ratio model, and the mathematical model between the excitation voltage period and the measured current which exceeded the measurement range was built by analyzing the working principles of the duty-ratio model digital sensor. In this way, the measurement range of the original sensor could be expanded to 1.5 times of its original. Meanwhile, without changing the hardware, the solution provided in this paper also solved the measurement failure problem of part of sensors when the any overcurrent situations happen in the system, such as overload or short-circuit. Besides, the sensor designed in this paper could achieve Level-0.1 measurement accuracy within range, and reach Level-2 over-range measurement accuracy, satisfying the demands of DC power supply system on leakage current measurement.

The step voltage carried on by personnel is researched when single-phase grounding fault of medium voltage shore power system occurs. The experiments are designed to measure resistance value from the coastline to the ground point and the resistivity of sea water. According to the data obtained from experiments, the finite element model is established though ANSYS, the potential distribution from the hull to the fault point is calculated when single-phase fault of medium voltage shore power system occurs, and the decay of surface potential in the wharf is obtained, especially drop speed of potential near the point of failure is paid close attention, the safety range of step voltage to terminal staffs is obtained.