Kun-Long Chen

This study involves the design of a hybrid excitation self-contained power supply using the finite element analysis software Maxwell 3D for model construction; considering the hybrid excitation optimization design as the goal, two structural improvement plans are proposed. The first radial hybrid design is intended for magnet fixation and entails improvement strategies to effectively fix the magnet while alleviating the phenomenon of magnetic saturation. The second axial mixing plan aims to increase the power density per unit volume of the magnet for output voltage optimization. The feasibility of each improvement strategy was verified through magnetic circuit analysis, focusing on optimization of the design direction. Moreover, the suitability of hybrid excitation was proven through hardware measurements. Accordingly, in an environment where the power cable transmission current was 300 A, the output voltage increased by as much as 50.18% over the pure silicon steel sheet (PSSS) type. Finally, regarding product development practices, the economic benefit was examined when specifically applied to drones. Macroscopically, applications are also considered for instances when there are no power supplies or when batteries cannot be replaced easily, such as in smart electricity meters and automated external defibrillators installed in inaccessible places.

The seismic resilience has become a critical concern for power systems for high-impact, low-probability disasters such as severe earthquakes. In order to enhance seismic resilience for power systems, a novel protective device, the Passive Over-Current Trip (POCT), has been designed in this paper. In the design, the POCT integrates a fuse and a mechanical switch, able to trigger the breaker to interrupt the circuit to ensure effective protection. The POCT has the trip-free feature as it fulfills its protective function without the need for an electric relay requiring a continuous power supply. The proposed POCT provides an immediate and reliable solution for the protection in high and ultra-high voltage applications. To validate the effectiveness of the proposed POCT, shockproof and tripping tests were conducted. A seismic test waveform from the Fukushima earthquake that occurred on March 11, 2011 was used to test POCT. Under such a severe earthquake, no structural or mechanical damage on the associated components in the POCT was found. Also, the POCT is also in compliance with IEEE 693 standard. Finally, various tripping tests show that the POCT can operate within 18 ms when a fault occurs in a power system, which is much shorter than that of a typical high-voltage fuse.

Newly built high-voltage sites are required to assess their impact on the environmental magnetic field (MF), and surveyors mainly conduct on-site measurements on foot. However, the measurement process often encounters the problem of harsh on-site environment, the measurement method is limited, and the evaluation results may be questioned. This study proposes a new environmental MF measurement method based on tunneling magnetoresistance (TMR) sensors. In this method, the designed TMR-based MF sensor is mounted on an unmanned aerial vehicle (UAV) to realize large-area and remote MF measurements. All the sensing signals are acquired and processed by the embedded system on the UAV. Additionally, the UAV is equipped with a GPS antenna and WIFI wireless communication. All the fundamental and harmonic components of the MFs obtained through signal processing are marked by the GPS satellite time and position. Subsequently, all data are wirelessly transmitted to the environmental MF monitoring platform via WIFI for real-time display and storage. The study also evaluates the electromagnetic field interference of the UAV with the designed MF sensor to determine possible errors in the MF measurement results and make corrections. Finally, experiments are conducted using seven different MF components to evaluate the accuracy of the proposed environmental MF measurement technique. Moreover, an actual field measurement is conducted to verify the feasibility of the proposed method for the environmental MF measurement.

An environmental electric field (EF) measurement technology is proposed, based on an unmanned aerial vehicle (UAV) for working in the vicinity of high-voltage overhead lines. In this technology, the designed EF sensor and selected distance sensor are mounted on the UAV to realize non-contact EF measurement. Based on a parallel capacitor plate structure, the designed EF sensor implements a single-axis EF sensing method that can be used to measure the EF values and their frequency around the overhead line. The selected distance sensor was used to ensure a safe distance between the UAV and the measured overhead line. Moreover, this distance sensor was used to mark the relative positional relationship between the overhead line geometry and the measured EF distribution. Following the integration of the sensing system on the UAV, the electromagnetic interference of the entire UAV system (including UAV platform, embedded system, distance sensor, and ZigBee wireless communication) was analyzed with the designed EF sensor to understand possible environmental EF measurement errors. The accuracy of the proposed technology was evaluated using an indoor model of a scaled-down overhead line. Moreover, an outdoor field measurement was conducted to verify the feasibility of the proposed technology for the EF measurement.

In this study, a long‐distance non‐contact current measurement method is proposed based on the non‐contact sensor array measurement technology, combined with a new current algorithm. The sensor array is a vertical array composed of three three‐axis magnetic field (MF) sensors that is placed on the ground plane below the measured overhead line. The proposed current algorithm can optimize the geometry of the overhead line using the spatial MF values measured by the sensor array and then the three‐phase currents can be calculated. To improve the accuracy of current measurement, the spatial MF model in the algorithm considers the influence of cable sag. It enables a more accurate coupling matrix between the measured overhead line and the sensor array to be established. Additionally, the current algorithm architecture is designed using a composite algorithm to more optimally obtain the best three‐phase current values. A scale‐down overhead‐line measurement system is developed to test the proposed current measurement method. The results show whether a cable sag exists when the three‐phase currents are approximately balanced, with errors less than 2.0%. Moreover, it can be determined whether cable sag exists when the three‐phase currents are unbalanced, with less than 3.4% errors.

With the growing infrastructure for overhead lines, the demand for overhead‐line condition‐monitoring technologies has become increasingly urgent. Traditional current transformers used to measure three‐phase currents are bulky and difficult to install, which further increases the cost of monitoring. In order to meet the current state assessment needs of transmission and distribution networks, this study uses a novel magnetic‐field sensor array to realize nonintrusive overhead‐line current detection. Based on the magnetic fields measured by magnetic‐field sensors placed on the ground under the overhead line, the proposed algorithm can be used to calculate the three‐phase current values. The proposed method does not require on‐site calibration before the field measurements are conducted. With partially known overhead‐line geometry specifications from utilities, the algorithm can optimize the overhead‐line geometry and finally achieve accurate current detection. The simulation and experimental results verify that the proposed current‐detection technique can accurately calculate the three‐phase currents of the overhead line with only three three‐axis magnetic‐field sensors.

To improve the efficiency of power transmission, high-voltage direct current (HVdc) transmission systems are crucial power-related development in many countries. This study proposes a contactless dc current measurement method suitable for on-site measurements of HVdc overhead lines. In this method, a vertical magnetic field (MF) sensor array (three layers and one three-axis MF sensor installed in each layer) is designed to measure the spatial MFs on the ground. With the spatial MFs measured by the sensor array and the overhead-line specifications obtained from utilities, the core current algorithm of the proposed method can accurately calculate the current values. In addition, we design a magnetic shielding mechanism to correct a dc offset that is inevitably output from each MF sensor. The dc offset includes the quiescent voltage of the self-circuit of the MF sensor and the output voltage of the MF sensor caused by the earth’s MF. Thus, this mechanism can effectively solve the problem in which the dc offset is misjudged as an MF formed by the measured current. The simulation results indicate that under arbitrary vertical sensor array placements, the core convergence condition (geomagnetic invariance) of the proposed current algorithm can improve the algorithm convergence. Finally, the experimental results verify the feasibility of the proposed method for the measurement of overhead-line current. Without conductor sags, all the current errors are less than 2% in both the 500- and 800-kV overhead-line scenarios. Moreover, even with serious conductor sags, all the current errors are still within 9%.

Traditional current monitoring devices (e.g. current transformers) for transmission and distribution (T&D) networks are mostly installed at substations, so real-time and accurate information on current is almost unavailable for on-site load current monitoring, imbalance assessment, and equipment maintenance. This increases the fault risk in T&D networks and degrades the reliability and quality of the power supply. To address such a situation, this study proposes an intelligent and contactless current measurement method. The proposed method uses only a small number of magnetic-field sensors and the conductor geometry specification of an overhead line obtained from utilities. The simulation results show that the proposed method can accurately calculate each phase current using only three magnetic field sensors. In addition, a scaled-down overhead line measurement system was built to test the proposed method. The experimental results verify the feasibility of the proposed contactless method for overhead-line current measurement with less than 10% maximum measurement error.

An accurate and cost-effective islanding detection is in a great need for distributed generation (DG) integration. An onsite contactless islanding detection scheme is proposed in this paper, based on a small number of tiny and portable electric field (EF) sensors. In contrast to the existing mainstream detection techniques, which are heavily depended on the instrument transformer measurement in substations, the proposed contactless scheme is able to be deployed on the ground below the overhead feeders, enabled by a compact EF sensor and the associated accurate frequency measurement algorithm. The effectiveness, robustness, efficiency and security advantages of the proposed method are investigated and verified by the simulations using various feeder configurations. It is further supported by the laboratory experiments based on a scale-down overhead feeder test bed.