For the new generation of high-performance aviation engines and Control Moment Gyroscopes (CMGs), this equipment is characterized by high speed, heavy load, high temperature, and lightweight. Relying solely on bearings is already difficult to meet its support and vibration reduction requirements. Therefore, squeeze film dampers have been proposed and widely used to control the vibration and stability of rotor systems. However, there is still a lack of detailed theoretical basis for the coupling mechanism between elastic ring deformation and oil film pressure, as well as the influence of elastic ring structural parameters on oil film pressure distribution. This article will conduct theoretical analysis and numerical simulation to address the above issues, and the research results will provide a theoretical basis for engineering design.

Currently, piezoelectric transducer (PZT) based sensing systems are the dominant method for detecting partial discharge (PD) via acoustic emission (AE) in gas-insulated switchgear (GIS). Nevertheless, standard PZT systems often struggle to satisfy the stringent operation and maintenance demands of contemporary power equipment. Numerous research teams have recently explored novel acoustic emission sensing technologies based on optical fiber interferometers. Despite these advances, most existing research has concentrated heavily on enhancing sensor sensitivity, often overlooking the potential for multiplexing. Consequently, true distributed sensing capabilities have not yet been fully realized. To address this gap, an acoustic emission detection method based on a dual Mach–Zehnder (DMZ) optical fiber interferometer is proposed in this paper. This method can not only detect high-frequency AE signals but also identify the AE source via the time difference of the arrival of signals at the two interferometers. The latter is crucial for realizing distributed acoustic emission detection of PD in GIS. Based on this methodology, key parameters for the DMZ optical fiber sensing system were designed, and an experimental platform was established to evaluate the response and localization performance of the sensing system. Furthermore, a PD detection experiment on a real 110 kV GIS was conducted to evaluate the detection ability of the system for metallic particle defects. Experimental validation demonstrates that the proposed DMZ sensing architecture can identify discharge events down to the hundreds of picocoulombs (pC) range. The system achieves a signal-to-noise ratio (SNR) approximately 5 dB higher than that of conventional PZT systems. Additionally, the system supports the serial multiplexing of 20 sensing units and achieves a localization error of 6.6 m for the locus of the AE signal activity in the optical path.

ABSTRACT With the growing integration of renewable energy and DC power electronics, power electronic transformers (PETs) are vital in AC/DC hybrid grids. Their core component, high‐frequency transformers (HFTs), operates under severe electrical and thermal stresses, such as high dv/dt, high switching frequencies, and elevated temperatures that exceed the limits of conventional epoxy (EP) insulation. These limitations necessitate advanced materials with improved thermal conductivity and electro‐thermal stability for multi‐field conditions. To address this challenge, a synergistic enhancement strategy was proposed by integrating BN nanofillers functionalized through a two‐step KH550/G‐POSS modification. This interface design enables simultaneous regulation of dielectric behavior, heat transport pathways, and processing characteristics. An optimized formula with 7 wt.% G‐POSS content, and 20 vol% BN@G‐POSS nanofiller loading promises an improved thermal conductivity (492.5%) and a reduced viscosity (3493 mPa·s) compared to traditional BN/EP. Furthermore, the composite exhibits robust resistance against electro‐thermal degradation under a 100 kHz electric field, as demonstrated by a significantly elevated partial discharge inception voltage (increased by 266.5 V) and a remarkably attenuated total discharge amplitude (decreased by 256.5742 V). Overall, the BN@G‐POSS/EP system shows strong potential for next‐generation HFTs and PETs, underscoring the importance of interdisciplinary material design in addressing reliability challenges in modern power electronics.

Objective The capability to monitor dissolved gases in liquids is critically important across diverse scientific and industrial fields, including environmental monitoring, chemical process control, biomedical analysis, and particularly power system diagnostics where dissolved gas analysis (DGA) serves as a primary method for assessing transformer health. Current detection approaches universally suffer from the necessity of gas-liquid separation prior to measurement- especially evident in conventional transformer DGA that relies on offline degassing chambers, introducing delays of several hours. Micro-nano fiber (MNF), leveraging their strong evanescent field effects and exceptional surface-to-volume ratios, demonstrate unique advantages for in situ gas detection by eliminating separation requirements. While flame-based melting and stretching techniques can produce MNF with high surface smoothness and diameter uniformity to meet precision sensing needs, traditional fabrication methods face three fundamental limitations: unclear quantitative correlations between process parameters (e. g., hydrogen-oxygen flow rates, fixture speed v(m), preset tapering length l(m)) and morphological features (waist diameter D-w,transition zone length L-t); heavy reliance on empirical adjustments leading to poor reproducibility; inability to controllably excite non-adiabatic effects essential for high-sensitivity interferometry. These challenges severely hinder the scalable production and field deployment of MNF-based probes. To address these problems, this study develops a computer-coordinated non-adiabatic MNF regulation technology, establishing quantitative parameter-morphology mappings to achieve precise dimensional control for high-sensitivity in situ acetylene detection in transformer oil, thereby eliminating offline degassing and enabling real-time fault diagnosis in power systems. Methods A systematic methodology for structural parameter control of non-adiabatic MNFs is implemented. First, the sensing mechanism is theoretically established via modal analysis: cylindrical MNFs immersed in transformer oil are modeled using Helmholtz equations, with HE1m mode characteristics are solved numerically via eigenvalue equations to determine effective refractive index neff and cutoff diameters. This identifies an optimal waist diameter range of 9.68-17.48 mu m (Fig. 3) for simultaneous HE11/HE12 mode propagation, while transition zone length L-t simulation results reveal that short Lt enhances HE11 to HE12 coupling and long Lt suppresses higher-order modes due to broken adiabaticity (Fig. 4). Second, a hydrogen-oxygen flame fabrication platform (Fig. 6) is constructed with computer-coordinated control of key parameters: flame nozzle movement, fixture translation, and preset tapering length. Parametric studies quantify individual effects, revealing v(m) and l(m) as dominant factors influencing D-w and L-t , leading to derivation of fabrication model. Finally, the experimental validation involves fabricating MNF probes with controlled D-w under a fixed L-t, integrating them into a photothermal interferometry system (Fig. 14) with pump light at a wavelength of 1530.37 nm, and evaluating dissolved acetylene detection performance across different concentrations under optimized excitation. Results and Discussions The non-adiabatic fabrication technique achieves exceptional morphological control, with waist diameter reproducibility at D-w=(13. 552 +/- 0.430) mu m (3.2 degrees o error) and transition zone length precision at L-t=(1599.00 +/- 33.96) mu m (2.1 degrees o error) across five production batches (Fig. 13), demonstrating significant improvement over conventional methods. Sensitivity tests reveal a strong inverse correlation between waist diameter and detection performance: reducing D(w)from 13.1 mu m to 9.9 mu m increases acetylene sensitivity from 0.23 mV/(mu L/L) to 1.01 mV/(mu L/L) (Table 1, Fig. 15), attributes to enhance evanescent field energy at smaller diameters. System evaluation confirms a 16 detection limit of 2.9 mu L/L for dissolved acetylene (Fig. 16), with noise characteristics establishing this threshold where signal became indistinguishable from background at mass fractions below 1.5 mu L/L. The 9 ms response time, measured through pulsed photothermal excitation tests, enables near-real-time monitoring capability. These results validate the quantitative parameter-morphology mappings while highlighting the critical balance between diameter reduction for sensitivity enhancement and manufacturability constraints for field deployment. Conclusions This study systematically investigates the sensing mechanism, collaborative fabrication process, and parameter control model of MNF for in situ detection of dissolved gases in oil. A methodology is established for fabricating MNF with high morphological precision through computer-coordinated hydrogen-oxygen flame modulation, achieving sub-5 degrees o reproducibility error in waist diameter and transition zone length. Critical quantitative mappings between process variables are derived, as shown in Eqs. 4 and 5, providing foundational model for batch production and resolving traditional reproducibility limitations. The optimized MNF configuration (Dw=9.9 mu m, validated by mode analysis) exhibits high-performance dissolved acetylene detection with sensitivity of 1.01 mV/(mu L/L), low detection limit of 2.9 mu L/L (16), and rapid response time of 9 ms, as enhanced evanescent field interactions at reduced diameter increase the sensitivity by a factor of 4.4 when the diameter is reduced from 13.1 mu m to 9.9 mu m. Integrated with photothermal interferometry, this system eliminates offline degassing-reducing analysis time from hours to seconds while preventing oil depletion in transformers and operates stably under realistic conditions (25 degrees C, 250 mW pump power, 50 Hz modulation frequency). By leveraging non-adiabatic mode interference to amplify photothermal phase modulation, this integrated approach advances in situ DGA technology and provides a scalable platform for next-generation optical sensors in power equipment diagnostics.

Optical fiber sensors (OFS), leveraging their intrinsic insulation and high sensitivity, hold significant potential for partial discharge detection in electrical equipment. To achieve high-sensitivity partial discharge detection, this paper proposes the OFS based on heterodyne interferometry. By introducing frequency shift in the reference arm of the intrinsic interferometric system using an acousto-optic modulator (AOM), the output signal is shifted away from the low-frequency region, which is typically dominated by noise. The OFS test platform was constructed to evaluate the detection performance of the OFS. For partial discharge detection in a typical model, the signal-to-noise ratio (SNR) of the OFS response waveform was 3.6 dB higher than that of the piezoelectric transducer (PZT). In the frequency domain, the OFS demonstrated a wider detection bandwidth and richer frequency information, enabling effective detection of signals in the 20 kHz to 80 kHz range. The results indicate that the developed OFS outperforms existing PZT sensors in detection performance and can serve as a valuable complement to current partial discharge detection methods for electrical equipment.

In power transformers, insulating oil deteriorates continuously due to aging, overheating, discharge, and other factors, accompanied by the production of characteristic gases such as H2, CH4, C2H2, C2H4, C2H6, and varying degrees of diffusion within the oil. However, due to differences in gas structure and insulation systems, the diffusion characteristics of characteristic gases in gas to liquid (GTL) insulating oil are not yet clear, and the interactions among multiple gas molecules remain unclear. In order to elucidate this diffusion mechanism, this study employs molecular dynamics methods to investigate the diffusion behavior of mixed gases in stationary GTL insulating oil at the microscopic level. By comparing the diffusion coefficients, trajectories, free volume fractions, and interaction energies of single-component, binary, and multicomponent gas systems, the influence of mixed gas addition on diffusion is analyzed. The results indicate that for single-component diffusion systems, the diffusion coefficients of gases in GTL insulating oil exhibit the order: H2 > hydrocarbon gases, and the diffusion coefficients of hydrocarbon gases are inversely proportional to molecular mass, with diffusion of different gases conforming to the "vacancy jump diffusion theory". For binary diffusion systems, the diffusion of gas molecules in mixed gas systems exhibits a synergistic effect, manifested by repulsive interactions between different gas molecules. Moreover, the addition of mixed gases reduces the interaction energy of CH4 with GTL insulating oil by 9.21 kJ/mol and that of H2 by 3.76 kJ/mol, respectively; the free volume fractions of H2 and CH4 increase by 27.5% and 113.7%, respectively, expanding gas movement space, weakening GTL's binding effect on gases, and increasing gas diffusion coefficients. Clarifying the diffusion characteristics of gases in GTL insulating oil will effectively serve the fault diagnosis of power transformers.

Fabry–Perot (F–P) sensing, as an effective method for partial discharge (PD) ultrasound signal detection, offers advantages such as electromagnetic interference resistance and high sensitivity. However, current research primarily focuses on the size and material of the diaphragm, with insufficient attention paid to diaphragm structure. In comparison, this study designs an acoustic-sensitive diaphragm with a grooved oil cavity structure, achieving a resonant frequency of up to 60 kHz and a peak sensitivity of 792.5 mV/Pa. Due to the presence of the cavity in the probe, the impact of oil pressure on reliability and sensitivity remains unclear. Therefore, the optical fiber sensor reliability evaluation device was designed to assess the sensor’s reliability under oil pressure. The results show that the sensor’s sensitivity decreases as oil pressure increases, with an amplitude reduction of approximately 46.7

The application of power semiconductor devices has increased the risk of partial discharge (PD) under high dv/dt voltage. However, high-resolution sensing systems are essential for accurately detecting PD under the special conditions. A builtin high-resolution fluorescent fiber sensor system is proposed for high dv/dt PD measurement. Considering the propagation discharge light, the generation, transmission, and photoelectric conversion of fluorescence, a mathematical model is established to characterize the relationship between fiber layout and the detected light intensity. The accuracy of the model is verified and the fiber probe parameters are optimized through PD measurements. On the basis, accurate PD detection and feature analysis are conducted under high frequency and high dv/dt pulse voltages. By comparing with conventional ultrahigh-frequency (UHF) and high-frequency current transformer (HFCT) sensors, the fluorescent fiber system shows superior performance sensitivity, resolution, and anti-interference abilities. Specifically, it offers high detection sensitivity, achieving nanosecond optical pulse oscillation-free acquisition with a 1.5-ns half-peak width the pulse output, much lower than 50 ns of HFCT. It exhibits a discharge detection rate comparable to UHF and the highest signal-to-noise ratio (SNR) output while avoiding electromagnetic interference (EMI). This research presents an effective approach for PD detection under high dv/dt voltage and has great potential for industrial applications.

High-power medium-voltage power electronic transformers (PETs) are core equipment to convert and control electrical power with high efficiency in hybrid ac/dc power grids. PET typically consists of functional semiconductor devices and high-frequency transformers (HFTs), and its reliability is vital to be assessed for the upcoming utilization. In this article, a reliability evaluation method for PETs based on one of the most prevalent topologies, i.e., MMC configuration, is proposed, where the operational conditions and the main components are accounted. First, the power losses and junction temperature distribution of insulated gate bipolar transistor modules used in the rectification, isolation, and inversion stages of the MMC-based PET are analyzed in detail. The device failure rate is then evaluated based on reliability assessment criteria. Second, considering that the insulation system is a particularly vulnerable point in the HFT unit, a PET system reliability model is constructed accounting for the series-parallel connection among components in the topology. Finally, the mean time to failure of the PET equipment with a 10 kW/20 kHz HFT prototype is estimated to be 1.42 years according to the proposed model, and the influence of switching frequency on PET reliability is further analyzed. The proposed PET reliability can provide as a theoretical reference for the optimized design and operational maintenance of promising high-power medium-voltage PET equipment in power grid.

Electrical equipment is prone to partial discharge (PD) during long-term operation, and conventional electrical detection methods are easily affected by electromagnetic interference in the field. This paper proposes an optical fiber sensing method to detect ultrasonic signals during the partial discharge process. A mathematical model of the core component optical fiber probe is established. The influence of material parameters on sensitivity is analyzed, and further finite element simulations are conducted to study the impact of size parameters on the resonant frequency. Based on the simulation results, a 60-meter thin-diameter optical fiber is wound around a polyetheretherketone (PEEK) core shaft with a diameter of 10 mm and a height of 12 mm. A model simulating discharge in oil is built to test the sensor. The results show that the developed optical fiber sensor can effectively detect ultrasonic signals using the proposed method, with a signal-to-noise ratio (SNR) of up to 41.5 dB.

Because of the complex electrical characteristics and detection difficulty of the series arc fault, it is prone to cause serious electrical fires. Especially, a large number of power electronic loads have been put into use in recent years, which makes the circuit topology more complex, further increasing the difficulty of series arc fault detection. In this article, series arcs are divided into long arcs and short arcs according to the differential behavior of fault currents under different arc lengths. By comparing the simulation results of series power electronic loads under various black box models and measuring the similarity of time series and other parameters, it is considered that the Cassie model with a smaller time constant is better than Mayr and its derived models. It can better reflect the oscillation of the long arc current in the time domain. Furthermore, an improved arc model is proposed in this article, considering the influence of the black box model time constant on high-frequency fault current oscillation of power electronic loads such as fluorescent lamps. The difference between the short arc fault waveform of the improved model and the actual waveform is reduced by an average of 16.07% compared to that before the improvement, which provides a reference for the accurate detection of series arc faults in power electronic loads.

Slip rings are critical components in space electromechanical systems. Since the advent of domestically produced space electromechanical products, safety incidents induced by conductive slip rings have occasionally occurred. The motion mechanism of slip-ring wear debris generated during long-term operation under vacuum, microgravity, and complex electromagnetic fields remain a significant challenge for aerospace engineers. To address this issue, this study designed an in-situ observation device for wear debris in space slip rings. The device simulates the actual operational conditions of slip rings in orbit, utilizing the microgravity platform provided by China's space station to conduct the in-situ wear debris observation experiments. The modular and replaceable design incorporates high-resolution visible-light cameras to image the generation, migration and distribution processes of wear debris, providing experimental data for analyzing its motion mechanism. The device passed rigorous ground tests and has been successfully operating in orbit for over two years, capturing wear debris generation and migration while monitoring transient electrical signal interruptions in slip rings. The acquired data lays a foundation for optimizing future slip ring designs.

Partial discharge (PD) detection is crucial for ensuring the safe operation of power transformers. Optical fiber sensors (OFS), with advantages of electromagnetic interference (EMI) resistance, inherent safety, and suitability for embedded installation, demonstrate significant promise for PD detection. The micro-optical fiber probe (MOFP) with compact size (diameter 10 mm, height 4.9 mm) is proposed, which ensures sensitivity while offering the convenience and versatility required for embedded installation. The implementation of the heterodyne interferometric demodulation topology is employed to enhance stability, while the optimization of system parameter combinations leads to an improvement in the detection signal-to-noise ratio (SNR) by 24.7 dB. In the lab, the developed OFS achieves a 62% and 223.3% improvement in the SNR for detecting ultrasonic signals propagating in solid and in oil, respectively, compared to the typical PZT (R15 alpha). In the field, the OFS was effectively installed inside the power transformer and detected PD ultrasonic signals, addressing the issues of EMI with HFCT and the installation difficulty and low sensitivity of PZT. The results substantiate that the developed OFS provides a novel, reliable and effective approach for PD detection in power transformers.

The substation plays a critical role in the construction of new power systems, and effective carbon emission accounting and monitoring are prerequisites for power carbon emissions reduction. The model for accounting the carbon emissions throughout the lifecycle of a substation is proposed, covering stages such as design, equipment (material) production, construction, operation, and recycling. The carbon emissions of a typical 500 kV high voltage substation are modeled and calculated at each stage, revealing that the total carbon emissions for the lifecycle amount to 289,350.61 tons of CO2, with the operation stage contributing to 92.71

As core components of increasing power density, the new generation wide bandgap (WBG) power semiconductor modules are advancing toward higher voltage levels. However, the reliability of packaging insulation serves as a significant constraint, notably concerning the insulation degradation induced by high temperatures working conditions within confined spaces. In this article, a simplified power module test model featuring a directed bonding copper (DBC) and silicone gel was established. Through partial discharge (PD) tests across temperatures spanning 25 degrees C-175 degrees C and different etching distances for substrate layout, the insulation degradation mechanism of power modules at varying temperatures is comprehensively explored. The results indicate an obvious reduction in the PD inception voltage (PDIV) with rising temperature, exhibiting an uptrend over 75 degrees C. Simultaneously, the discharge amplitude initially increases and subsequently decreases with rising temperature. The thermal expansion of tiny air-gap defects within the silicone gel emerges as a significant factor influencing the module's insulation characteristics. Ultimately, by establishing a proportional air-gap defect model, the electric field and space charge distribution were studied under electrothermal coupling, validating the effectiveness of the insulation defect mechanism.

As critical transformer components providing electrical connectivity and external insulation, bushings are prone to thermal failures. The thermal behavior of typical 110 kV oil-impregnated paper capacitive bushings under varying loads using multi-physics modeling is investigated in this paper. The model integrates Joule heating, dielectric losses, internal fluid flow, surface radiation, and solar irradiation. Under solid conduction, a significant lateral temperature difference arises, amplified by radiation. Solar irradiation elevates surface temperatures by ~6°C, increasing shed asymmetry. Maximum temperature gradients in the porcelain insulator occur under high load. Conductor temperature differences rise substantially with load, reaching 29.5°C at full load. Internal fluid flow stabilizes near 0.25 m/s, reducing surface temperature by ~4.5°C via convective cooling. Simulated temperature profiles closely match field IR thermography. These results enhance understanding of bushing thermal distribution, especially surface-to-surface radiation and solar radiation on bushing temperature, supporting improved thermal management and reliability design.

Slip rings are extensively employed in spacecraft mechanisms. Owing to current-carrying tribological processes during operation, particulate debris generation remains inevitable, which has been consistently identified as a critical contributor to in-orbit failures of space mechanisms. This paper presents the design and implementation of a slip-ring debris experiment control system currently operational onboard the China Space Station. The experimental system serves dual purposes: (1) establishing controlled electromagnetic environments and (2) implementing real-time monitoring of debris generation dynamics and post-deposition morphological characteristics. The primary research objective focuses on elucidating particulate migration mechanisms under combined vacuum conditions, microgravity effects, and superimposed electromagnetic fields.

A novel SMA-actuated bistable beam was fabricated and investigated to fulfill load adjustment in this study. The SMA curved beam actuator was connected with the compliant beam, implementing both load bearing and self-actuating. The prototype and the fabrication process of the bistable mechanism were also developed. Considering multiple inflection points in the deflection curve, the bistable snap-back mechanism was modeled and analyzed through large deflection theory. Moreover, the moment–angle curve, the evolution of deflection modes, and the energy landscape were presented. The key characteristic of the studied bistable system was the capability of horizontal load adjustment during snap-back, which was employed to design the fully compliant mechanisms with variable ranges of load adjustment. Experiments were conducted to test the performance of load adjustment. It was found that the decrease of horizontal load could be reached. The adjustment range of horizontal load could be controlled through the geometric parameters of compliant beam and SMA curved beam actuator. Moreover, the bistable beam could be reset by applying a concentrated force and cycling actuation test was conducted to confirm that point. The proposed bistable mechanism is compact, self-actuating, and fully compliant, implying the potential application in programmable structures and metamaterials.

Continuously rotating gimbals for scanning purposes are widely used in space applications. For high-precision gimbals, it is essential to lock the gimbal before launch and unlock it on orbit. This kind of gimbal puts forward the need for hold down release mechanisms that are able to clear the gap between the rotating and fixed parts at release. Existing technologies either lack the function of gap avoidance after separation or rely more or less on the elastic deformation of the structure or limited spring forces for unlocking, which are either unreliable or complicated. To address this problem, this paper presents the design of a novel non-pyrotechnic heavy-load hold down release mechanism (HDRM) based on shape memory alloy actuator. The proposed HDRM is shock-free and capable of clearing an axial gap of 8 mm for safe rotating at release. The structure and operational principle of the proposed design are straightforward. Detailed tests show the proposed HDRM may withstand a maximum external force of 50 KN with relatively high stiffness under 15 KN of preload, indicating a better performance than existing products. The HDRM demonstrates its promising usage as an alternative to traditional pyrotechnic and non-pyrotechnic HDRMs.