Polypropylene (PP) based power cables are recognized as a potential solution for large-capacity power transmission due to their superior electrical strength and high operating temperature. Evaluating the aging process of cable materials is crucial for safe operation. This paper focuses on the effect of metal involved aging process on the conductor shielding layer. Conducting the 27-day accelerated aging experiment, the influence of the contact of polypropylene-based shielding layer with Cu and Al conductors on degradation performances is compared and the effect of metal deactivator is assessed. The results show that the diffusion of copper ions and thermal oxidation reduce the thermal stability of the shielding layer and lead to a chemicrystallization effect. The aging effect is manifested macroscopically as the deterioration of mechanical properties and the increase in electrical resistivity. Cu-contacted samples perform severer degradation than Al-contacted samples. While the presence of metal deactivator greatly suppresses the diffusion of copper ions and inhibits their catalytic activity by forming complexes, making the degradation in Cu-contacted materials significantly reduced. Finally, a mechanism is developed to associate the macro-property reduction with the crystal structures variation during aging. This work provides a reference for evaluating the aging of PP cables and developing shielding materials.

As the next generation eco-friendly cables, polypropylene (PP) insulated cables currently lack clearly specified test standards and operating criteria. This study comprehensively evaluates the thermal, electrical, and mechanical properties of grafted PP cable materials over a wide temperature range using quantitative approaches. Variations in material performance during thermal cycles are attributed to the evolution of crystal structure. Based on performance parameters, a simulation model of multi-field coupling was established to assess both normal and short circuit operations of cables. The feasibility of grafted PP cables working above the prevailing maximum normal operation temperature is discussed according to temperature and electric field distribution analysis. And thermal process, electric field behavior, and conductor eccentricity of cable under short circuit conditions described in IEC standards are also analyzed in detail. The results show that the PP cable still works normally after a prescribed short circuit fault with a maximum conductor temperature of 250 °C for 5 seconds. According to the operation characteristics of cables, the relationship between the short circuit current, duration and the maximum conductor temperature is calculated for the operating guideline. This paper provides an important simulated reference case for evaluating the safe operating limitation of the thermoplastic PP insulated cable operation.

Harsh-environment requirements of electrical and electronic systems demand advanced dielectrics with high energy storage density at elevated temperatures. Heat-resistant polymers are usually designed with densely packed molecular chains to maintain structural integrity. Unfortunately, the narrowed inter-chain spacing causes severe charge transfer under high electro-thermal fields, prohibiting capacitive energy storage beyond 200 °C. Here we report hyperbranched dielectric polymer networks as a solution to the persistent challenge. The hyperbranched topological junctions not only transform the linear polymer chains into a robust network to tolerate thermal stress, but also expand the inter-chain spacing to inhibit charge transfer. Results suggest that the hyperbranched networks exhibit suppressed secondary chain relaxation alongside expanded free volume. Moreover, the customizable chemical structure of hyperbranched centers renders this method general to capacitive polymer design. The hyperbranched polymer networks exhibit an exceptionally high discharged energy density of 4.9 J/cm3 above 90% efficiency at 250 °C, surpassing the existing polymeric dielectrics.

Dielectric capacitors featuring high energy density and excellent temperature stability are vital to the miniaturization and reliability of high-power electronic systems. Antiferroelectrics (AFEs) exhibit high polarization through field-induced phase transition. However, their antiferroelectric-ferroelectric phase transition electric field (EAFE-FE) usually exceeds the dielectric breakdown strength, severely restricting their practical energy storage capability. To address this issue, we propose an antiferroelectric/relaxor ferroelectric composite strategy that effectively reduces the EAFE-FE by tuning the phase transition energy barrier, thereby facilitating field-induced polarization switching. The Pb0.94La0.04(Zr0.84Sn0.15Ti0.01)O3/2 wt % 0.8Ba(Zr0.1Ti0.9)O3-0.2 Bi(Zn2/3Ta1/3)O3 (PLZST/2BZT) composite ceramics exhibit a high recoverable energy storage density (Wrec) of 9.3 J cm-3 and an energy storage efficiency (η) of 85% when subjected to a breakdown electric field of 325 kV cm-1. This remarkable performance is owing to the reduced phase transition energy barrier and the enhanced interfacial polarization, which collectively strengthen polarization response. Notably, the PLZST/2BZT ceramics also exhibit exceptional temperature stability, maintaining Wrec above 6.5 J cm-3 and η invariably surpassing 81% over a broad temperature range of -20 to 140 °C under a 320 kV cm-1 electric field. These results highlight the effectiveness of the AFE/relaxor ferroelectric composite strategy for achieving high-performance dielectric ceramics, providing valuable insights into the design of high-performance capacitors for advanced dielectric materials and high-power electronic devices.

In the previous part, simulation works were conducted to analyze the field grading effect of nonlinear materials in the application of bushing, and the aim of this paper is to present the experimental investigations. The adaptive field grading (AFG) bushing samples are prepared by a novel method based on wet winding technology, and the assembly quality is verified by scanning electron microscope, thermal gravimetric analyzer, and conductivity test of slice samples with multi-layered structure. The initial partial discharge voltage and phase-resolved partial discharge pattern characteristics of the AFG bushing samples are obtained. Taking S0 without a field grading layer as the control group, it exhibited noticeable internal partial discharge at 36 kV. At the same time, S2 and S3 samples with nonlinear materials had higher initial partial discharge voltages, which are 66.67% and 38.89% higher than those of the former samples, respectively. The insulation strengths under the lightning impulse voltage of the AFG bushing samples are also tested. The S0 sample was broken down under severe high-voltage impulses, while the S2 sample remained well-insulated after 15 positive and negative lightning impulses. It is hoped that this work will provide an innovative technical roadmap for bushing design and manufacturing.

Field grading materials hold significant potential for power equipment application owing to their ability to suppress electric field distortion. However, achieving synergistic regulation of their multi-physical properties remains a challenge beyond merely modulating nonlinear conductivity. Inspired by the "vein-and-flesh" structure of natural leaves, ZnO microvaristor/epoxy composites reinforced with a polyester fiber network via a wetwinding process. We fabricated ZnO microvaristor/epoxy/polyester fiber composites via a wet-winding process. In this biomimetic design, the polyester fiber network acts as a skeleton that regulates filler distribution. By modulating the network density, we achieved the coordinated regulation of the electrical, thermal and mechanical properties of composites. Results show that composites become electrically nonlinear at filler contents above 35 vol%. At a fixed filler concentration, the threshold electric field and nonlinear coefficient can be precisely tuned by the fiber network density. A moderate density (70 g/m2) yielded the optimal thermal conductivity (0.648 W & sdot;m-1 & sdot;K-1 at 35 vol% loading) and mechanical performance, enhancing flexural strength by 41.8% at the same loading. This work provides a novel strategy for designing high-performance field grading materials through fiber network density regulation.

Lithium niobate (LN) Rayleigh surface acoustic wave (SAW) devices provide a compact platform for solid-state electric-field (EF) sensing, but their sensitivity depends strongly on substrate orientation, EF direction, and package-induced mechanical boundary conditions. This work presents decoupled sensitivity measurements, prototype-level noise evaluation, and package-aware modeling for LN Rayleigh-SAW EF sensors. Dual-channel two-port delay lines were fabricated on 128∘ Y, Y, X, and Zm cuts, with electrode layouts that separately generate normal and in-plane transverse EFs. Direct phase detection and frequency-mixing readout give consistent sensitivity coefficients after group-delay and phase-to-frequency normalization, respectively, despite passband ripple induced by multiple-transit echoes. The largest measured linear sensitivity magnitude reaches 78.2×10−12 m/V for the 128∘ Y-X configuration under normal EF, while the strongest measured in-plane response reaches 16.0×10−12 m/V for the X-3.5m configuration. These measured sensitivities extend the available experimental data beyond previously reported standard configurations and provide reference values for model assessment. Zero-field noise analysis of a representative 128∘ Y-X normal-field oscillator readout gives a DC minimum noise-equivalent field of 83.3 V/m at 13 ms and an AC spectral noise-equivalent field of 4.75 V⋅m−1⋅Hz−1/2 at 500 Hz. A 3D finite element model including adhesive compliance, PCB support, and electrode geometry is further combined with a wave iterative calculation to evaluate EF-induced velocity perturbation. The nominal calculations provide semi-quantitative trend information and reproduce the negligible nominal linear response of the experimentally quadratic-dominant X-3.5m normal-field and Y-Z in-plane configurations. However, Monte Carlo propagation of third-order material-constant uncertainty and unresolved discrepancies in some configurations indicates limited absolute predictive capability. The workflow is therefore interpreted as a package-aware, semi-quantitative tool for sensitivity-trend analysis, substrate-orientation screening, and package-structure assessment under specified package conditions. The combined results identify the 128∘ Y-X orientation as a strong candidate for normal-field sensing and suggest X-cut propagation-angle regions near −80∘ and 30∘ as qualitative candidates for future in-plane sensing studies.

To optimize the linearity and sensitivity of tunneling magnetoresistance sensors, this work quantitatively investigates the dependence of internal bias field non-uniformity on the device aspect ratio. Based on a discretized bias field model that accounts for the inhomogeneous magnetization reversal process, the transfer curves of magnetic tunnel junctions with various geometries are analyzed. The study reveals that the non-uniformity of the internal bias field exhibits a significant non-monotonic trend as the aspect ratio increases. Specifically, the field variation initially rises due to edge effects but subsequently decreases in longer devices. These findings provide a theoretical basis for geometric optimization, demonstrating that an appropriate aspect ratio is critical for balancing sensitivity and field homogeneity.

Bushing has become a critical component endangering the safe functioning of power transmission and limiting its development to higher voltage and power levels. The main technical bottleneck that restricts high voltage bushing is the uneven distribution of electric fields due to its “plug-in” structure. In this paper, a novel adaptive field grading (AFG) bushing with a simple multi-layered structure based on nonlinear materials is introduced. A frequency-domain steady-state simulation method considering the field-dependent dielectric and loss characteristics of nonlinear materials to design the AFG bushing is proposed. Referring to the size of the AC transformer capacitive bushing, the finite element models of the 40.5 kV AFG bushing are established, and the electric field distributions are obtained. Optical electric field sensors are used to test the surface electric field distribution of the bushing samples, validating the accuracy of the simulation method. Combining simulation and experimental test results, the influence of doping concentrations and lengths of the field grading layer on the electric field distribution is studied, and the grading mechanism of nonlinear material is summarized. The results demonstrate the potential of nonlinear materials to relieve electric field concentration in bushings and provide a solid basis for its design and application.

With the rapid expansion of emerging applications requiring high efficiency, high power density, and fast switching speeds, (ultra) wide bandgap ((U)WBG) power electronic modules are increasingly replacing conventional silicon-based counterparts due to their superior electrical, thermal, and switching characteristics. As a widely used encapsulation material, the dielectric properties of silicone gel (SG) determine the operational reliability of power modules. Therefore, the breakdown behavior of SG under practical high–slew-rate square-wave stresses warrants investigation. In this paper, the breakdown tests under bipolar square waves with various rise times at a fixed 50 kHz frequency were conducted on SG samples. Results show that the breakdown voltage of SG is positively correlated with the rise time: As the rise time decreases from 250 ns to 50 ns, the mean breakdown voltage drops from 4.60 kV to 2.79 kV, with a 39.35% reduction. A two-parameter Weibull analysis indicates steep slopes (β≫1) across conditions, implying relatively clustered breakdown voltages; shorter rise times tend to preserve high determinism while lowering characteristic strength. The breakdown behavior is interpreted by space charge dynamics. This study highlights the critical importance of incorporating waveform parameters into the insulation design and evaluation process for (U)WBG power modules.

The design of dielectric polymers for extreme-temperature energy storage faces the challenge that the structural optimization towards improved insulating/capacitive performance is usually at the expense of reduced thermal resistance. Here, we present a design of high-temperature dielectric polymers that does not rely on any specific chemical structures that compromise the thermal resistance, but capitalizes on the disordered combining sequences of monomers that are all of high thermal resistance, thus improving the capacitive performance while maintaining the temperature capability. The high positional and energetic disorders were demonstrated in the polyimides by design, synthesized through co-polymerization with an optimal combination of 13 monomers. The enhanced disorder of molecular chains was found to regulate the inherent charge transport behavior of polymers, leading to approximately 2 orders of magnitude augmentation in electrical resistivity and unprecedented capacitive performance at an extremely high temperature of 300 degrees C.

Electron transfer and transport constitute the fundamental mechanisms governing the performance of polymeric dielectrics, yet their microscopic nature remains elusive due to the intrinsic complexity of aperiodic condensed states. This investigation presents, for the first time, a computational-experimental exploration on quantitative, real-space orbital electron transfer and quantum electron transport, which have been largely overlooked in aperiodic systems. The energy barrier and spatial confinement of unoccupied frontier orbitals play a pivotal role in regulating electron transfer, which is predictable and experimentally characterizable, and dictates dielectric performance. Additionally, the structure-dependent quantum current strongly influences the macroscopic conduction characteristics. These insights enable precise regulation of dielectric performance via chemically superseding frontier orbitals. We hence apply this approach to a typical polymeric system and propose a design principle comprising three ab-initio descriptors. Our results substantiate the validity of this rationale, offering renewed insights into electron dynamics in aperiodic systems and guiding future dielectric design.

As the adoption of (ultra) wide bandgap ((U)WBG) power modules accelerate, ensuring reliable dielectric performance in soft encapsulation materials such as silicone gel (SG) has become a pressing challenge. Existing studies on SG have primarily focused on partial discharge (PD) and electrical treeing under DC or low-frequency AC excitation, with limited attention to dielectric breakdown—despite its critical role in defining insulation failure thresholds. Moreover, few efforts have explored the effects of high-frequency waveforms that closely mirror the fast-switching transients typical of practical (U)WBG applications. This study investigates the dielectric breakdown characteristics of SG under three voltage stress conditions: DC, 60 Hz sinusoidal AC, and high-frequency bipolar square waveforms (10–50 kHz) with a fixed 50 ns rise time. Experimental results reveal a significant, frequency-dependent reduction in breakdown voltage under square wave stress, underscoring the vulnerability of SG to rapid voltage reversals. A two-parameter Weibull statistical analysis further quantifies this degradation, showing increasingly clustered failure distributions at higher frequencies. The breakdown behavior is interpreted through the interplay of space charge dynamics and the time-dependent self-healing response of SG. These findings highlight the importance of accounting for waveform characteristics—not just field strength—when evaluating insulation reliability in UWBG power modules and provide a data-driven basis for future encapsulation design strategies.

As dielectric polymers are confined to nanoscale dimensions, anomalous enhancements in electrical resistivity have been widely inferred and exploited in nanocomposites and multilayered structures—yet direct experimental validation of the mechanisms remains elusive. Herein, we unveil the physical origins of this abnormal resistivity at the nanoscale through a model polymer approach. Direct experimental observations on ultrathin polymer films (down to 5 nm) reveal that the size‐dependent enhancement in electrical resistivity primarily originates from confined local β‐relaxation processes, complementing conventional explanations based on changed molecular packing and density. With this insight, we (i) rationalize the temperature‐dependent effects of nanofilling in polymer‐nanocomposite dielectrics and (ii) engineer a commercial polymer film with a bulk glass transition temperature of 237 °C that retains stable insulating performance up to 300 °C. These findings provide a unified framework for molecular‐dynamics‐driven charge transport and offer a strategy to design thermally robust dielectrics for next‐generation electronics, power modules, and harsh‐environment applications. image

It is of great significance to locate faults in distribution systems quickly. Traditional methods for locating fault sections in distribution networks are mostly based on rules or physical models. However, with the increasing complexity of the topological structure of distribution networks and the increasing number of distributed power sources, traditional methods are difficult to meet the current needs of locating fault sections in distribution networks. Based on this, this paper proposes a fault section location scheme for distribution networks based on wavelet energy entropy and artificial neural networks. First, the effective values of voltage and current data are extracted to train the model, and correlation analysis is used to optimize the features. An improved IEEE33 node data set containing distributed power sources was built, and different types of fault data at different section locations were simulated. The proposed method was used for training and verification, which demonstrated the rationality and applicability of the proposed method. It could reach 97.38%.

As an effective method to enhance the dielectric performance of polyolefin materials, polar side group modification has been extensively applied in the insulation and energy storage materials of electrical and electronic systems. In this work, two side groups with different topological structures were adopted, namely, vinyl acetate (VAc, aliphatic chain) and N-vinyl-pyrrolidone (NVP, saturated ring), to modify polypropylene (PP) via chemical grafting, and the effects of structural topology of the polar side group on the microscopic and macroscopic characteristics of PP, particularly on its electrical anti-breakdown ability, were investigated. Experimental results showed that the side group structural topology directly affected the crystallization and thermal properties of PP. The in-depth computational analysis indicated that the grafted NVP possessed a lower deep trap depth than VAc, which is related to the topological structure and corresponding orbital interaction within the side group. Furthermore, molecular dynamic (MD) simulations revealed the presence of a saturated ring in the NVP side group that led to more free volume within the material's condensed state than VAc. Therefore, by contrast, VAc-grafted PP with deeper trap orbitals and less free volume exhibited higher breakdown strength enhancement up to 21% and 14% at 30 and 90 °C, respectively. Thus, this work provides a novel understanding of the topological structure effect of the side group on the macroscopic dielectric performance from the viewpoint of microscopic physical chemistry. Furthermore, this work would serve as a reference for the refined design and property modulation of dielectric materials in modern electrical power facilities.

The demand for innovative digital grid technologies necessitates the development of high-frequency (HF) current measurement techniques, extending into the tens of MHz range, to enhance power grid monitoring capabilities and monitor discharges in power equipment. However, monitoring of HF partial discharge current remains challenging for the current sensor because of the limitations imposed by the restricted bandwidth of the magnetoresistance chip and the back-end circuitry of the sensor. Therefore, a 20-MHz wideband current sensor is designed employing a tunnel magnetoresistance (TMR) bridge chip optimized for the frequency band. The factors that affect the bandwidth limitation of TMR current sensors are examined. On one hand, by enhancing the frequency response of the TMR chip, we successfully fabricated chips with a bandwidth exceeding 50 MHz, representing a significant improvement compared to commercially available chips limited to only a few megahertz. On the other hand, optimization strategies were implemented for expanding the bandwidth of printed circuit board (PCB) integrated TMR current sensors, resulting in a maximum achievable bandwidth of up to 20 MHz. The developed sensors were tested to measure the discharge current in a needle-plane electrode, thereby confirming their suitability for HF discharge current measurement.

Current measurement technology based on tunneling magnetoresistance (TMR) sensors has attracted significant attention due to advantages such as high accuracy, low cost, wide bandwidth, and compact size. However, hysteresis phenomena inherent in TMR sensors severely limit their accuracy and applicability. This study proposes an improved Preisach-type model specifically designed for hysteresis compensation in TMR sensors. Experimental validation confirms the effectiveness of this compensation method. Compared to conventional linear models, the Preisach-type model significantly enhances measurement accuracy and stability under complex magnetic field variations, achieving measurement errors below 0.5%.

High-voltage overhead transmission lines are susceptible to abnormal conditions such as icing, wind deviation, and galloping due to extreme weather conditions, which has a serious impact on the safe and stable operation of the power system. Therefore, it is necessary to establish an online monitoring system to identify and warn the abnormal conditions that may occur on overhead transmission lines in real time. In this paper, a scheme of transmission line state identification based on electromagnetic sensing data and machine learning method is proposed. Firstly, the catenary model of transmission line is modeled and analyzed, and the mathematical expression of the model in abnormal state is defined. Then, based on the law of spatial magnetic field and electric field distribution of overhead transmission lines, the installation strategy of sensors is discussed, and the feature quantities that can be used for machine learning are constructed. Finally, the electromagnetic field data is calculated and generated based on the specific sensor deployment scheme, and the task instance of transmission line state identification is completed based on the idea of machine learning.