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The short‐circuit withstand capability of the transformer is crucial to the reliability of power systems. Research on the short‐circuit characteristics of windings is the basis for improving the stability of power transformers. Although many studies focus on electromagnetic force and cumulative deformation of two‐winding transformers, there is a lack of careful comparison of the electromagnetic and mechanical characteristics of three‐winding transformers, as well as the cumulative effect of stress, displacement and strain. In this paper, the model is established to study temporal response and spatial distribution of the electromagnetic and mechanical properties under short‐circuit impacts. The results show that the short‐circuit effects on medium and low‐voltage windings are more severe than on high‐voltage windings. The first current peak will lead to the greatest threat. Second, the influences of iron core and pre‐stress on short‐circuit characteristics are investigated. The characteristics of windings differ between inside and outside the iron core window, which is pronounced for high‐voltage winding. Besides, the greater pre‐stress is not better for the stability of windings. Finally, it is found that the residual stress and displacement continue to accumulate and the plastic strain appears under multiple short‐circuit impacts. This work is helpful for the analysis of short‐circuit withstand capability of transformers. © 2023 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

The extended grading capacitor (EGC) is a cost‐effective technique to suppress secondary arc. However, whether the use of EGC would weaken the interrupting capability of circuit breakers (CB) or not is still undetermined. In this work, an equivalent circuit model for ultra‐high voltage transmission line was established. The expressions of transient recovery voltage (TRV) across the contact gap of CB are derived, and hence the rate of rise of recovery voltage (RRRV). Then, a series of simulations have been performed, including the long‐line fault, the short‐line fault (SLF) and the terminal fault. It is found that the RRRV had approximately linear downward trend with the increase of the capacitance of EGC under long‐line fault but had approximately index downward trend under SLF. The SLF poses the strictest requirements to the CB. In addition to suppressing secondary arc current, the use of EGC would mitigate the interrupting severity and enhancing the interrupting performance of CB. [ABSTRACT FROM AUTHOR]

An improved model for the motion dynamics of a metallic particle located in the non‐uniform electric field area in the gas insulated system is proposed. To represent the special area, a diverging conducting electrode is used in this study. Based on the fluid mechanics theory, the forces imposed on metallic particle are first developed. The motion process is then divided into two modes, i.e. the particle rolls on the electrode surface and moves in the gap. The collision and reflection processes between the particle and the electrode are crucial to the motion, and they are fully considered in the proposed model. The trajectory of the particle under different voltages is obtained. The evolution of metallic particle is divided into four stages, and it is featured by four quantities, i.e. the critical jumping point, the minimum horizontal position, the falling point, and the motion time. The characteristics for each stage are analysed, and the sensitivity analysis of the quantities are performed. The impacts of the applied voltage, the particle radius, the initial position etc. are discussed. The results provide guidance for particle trap design. [ABSTRACT FROM AUTHOR]

In this study, the ultra‐high‐frequency (UHF) antenna for partial discharge (PD) detection is optimised to simultaneously satisfy the requirements of low return loss and high fidelity factor (FF) in the frequency band of interest by using the modified non‐dominated sorting genetic algorithm II (MNSGA‐II). Based on the labour division strategy, the MNSGA‐II adopts an adaptive crossover and mutation possibilities instead of the fixed ones, resulting in the significant improvement of convergence rate and exploration ability. One of the Pareto‐optimal solutions is presented as the authors' proposed UHF antenna, whose performance is compared with those of both the antenna optimised by genetic algorithm and the existing wideband antennas. The experimental results show that the proposed antenna with a compact size of 0.201 λL × 0.198 λL realises the reflection coefficient less than −10 dB from 490 MHz to 1.52 GHz, and its FFs in the face‐to‐face and side‐by‐side scenarios are 0.897 and 0.845, respectively. Furthermore, the simulation results reveal that the high FF of antenna greatly increases the accuracy of PD source localisation. It indicates that the MNSGA‐II provides an excellent solution to the multiobjective optimisation problems in antenna design. [ABSTRACT FROM AUTHOR]

An experimental and testing platform was established to comparative study the decomposition characteristic of SF6 under different voltage waveform (negative direct current (DC) voltage, positive DC voltage, and alternating voltage), and investigate the influence of pressure and adsorbent. Content variation of typical products under different conditions and the influence mechanism were observed and analysed in detail. The results indicate that SF6 decomposition characteristics are closely related to a voltage waveform, pressure, and adsorbent. Concentrations of by‐products under AC voltage are higher than those under DC voltage and SF6 decomposes more easily under positive voltage than negative voltage, which can be explained by different discharge energy and distribution characteristic of space charges. The values of typical products show an obvious downward trend with pressure due to falling discharge energy, volume of active region and dissociation rate of SF6. Concentrations of typical products including SOF2, SO2F2, and SO2 decrease dramatically after adding adsorbents because of physical absorption and chemisorption. [ABSTRACT FROM AUTHOR]

Corona discharges on high‐voltage transmission lines cause the problems of energy waste and electromagnetic interferences. Previous studies on negative DC corona discharges are mainly on the effects of various environmental factors on the corona inception voltage, Trichel pulse frequency etc. However, few researches are focused on Trichel pulses‐pulseless glow mode transition, and their transition mechanisms are still lacking. In this paper, a vacuum vessel is built up in which the humidity and pressure can be accurately controlled to simulate corona discharges under different climatic conditions. The pressure range is 50–101 kPa and the relative humidity (RH) is 10–90%. A needle‐plane electrode with different radius of curvature is used to produce negative corona discharges. It is found that the transition voltage increases with the RH and air pressure. A higher humidity results in the formation of hydrated ions with lower ion mobility and the increase in the gas temperature around the needle electrode. The experimental results demonstrate that the effect of reduced ion mobility is greater than the gas temperature rise. Furthermore, an interim process, in which the Trichel pulses and the pulseless glow exist simultaneously, appears during the discharge modes transition for the needle electrode with a larger radius of curvature. [ABSTRACT FROM AUTHOR]

With the development of smart grids, efficient condition monitoring of high voltage transmission system has become crucial, necessitating reliable power supplies for distributed sensors. Traditional energy harvesters often focus on either internal or external sources, limiting overall efficiency. This study introduces a triboelectric‐electromagnetic‐electric field hybrid energy harvester (TEE‐HEH) that synergistically integrates triboelectric nanogenerators (TENGs), electromagnetic generators (EMGs), and electric field energy harvesters (EEHs) to simultaneously capture electric field and wind energy. Electric field energy is harvested via displacement currents between transmission lines and the ground, while TENGs and EMGs efficiently capture low‐ and high‐speed wind energy, respectively, enabling broadband harvesting (2.3–10 m s−1). The synergistic combination of TENG, EMG, and EEH within the TEE‐HEH leads to significantly enhanced energy capture efficiency from multiple sources. At a wind speed of 5 m s−1, a transmission line voltage of 25 kV, and a distance of 1.5 m, the TEE‐HEH achieved peak power outputs of 18.5 mW (TENG), 262 mW (EMG), and 1.85 mW (EEH), demonstrating enhanced energy collection efficiency. An environmental monitoring system has been powered, demonstrating the TEE‐HEH's practicality for dual‐source energy harvesting in smart grid applications. [ABSTRACT FROM AUTHOR]

Triboelectric nanogenerator (TENG) has received significant attention as an energy harvesting technology capable of converting mechanical energy from the environment into electrical power. However, due to its inherent high impedance and low charge transfer output characteristics, the output of TENG is often relatively small. Current research typically focuses on switching on and off under intrinsic voltage for performance management. To further improve output performance, an energy management strategy is proposed that aimed at voltage boosting in this study. This strategy ingeniously designs the discharge sequence of two discharge switches to adjust the connection between the intrinsic capacitor and the matched capacitor, thereby facilitating instantaneous charge transfer under voltages surpassing the intrinsic voltage and significantly enhancing the power density. Combining this strategy with a power converter has significantly enhanced the energy storage efficiency of capacitors, thereby enabling improved power supply for sensor devices. Moreover, experimental results show a power density of 324.8 kW m−2, indicating a 100% increase compared to the direct discharge strategy. With such high output power, five parallel 10‐watt commercial lamps can be illuminated. This strategy introduces a novel idea for achieving high performance output from TENG. [ABSTRACT FROM AUTHOR]