Search Results (143)

Accurate identification of early-stage insulation aging in 10 kV cross-linked polyethylene (XLPE) cables is required for reliable operation of urban power distribution networks. In this study, the frequency- and temperature-dependent vector impedance under operating-voltage-relevant electrical stress was investigated for insulation aging assessment. Cable specimens were thermally aged at 135 °C for 0, 7, 14, 21, and 28 days. Fundamental capacitance and polarization–depolarization currents were measured at different temperatures to characterize the aging response. An operating-voltage-relevant broadband impedance circuit was then constructed, and synchronized voltage and current waveforms were acquired under 6 kV excitation from 100 Hz to 0.1 Hz at different temperatures. The fundamental capacitance and the fitted current constant b_n decreased with aging time, indicating that the insulation remained in the early stage of aging. The phase difference and impedance magnitude extracted from the measurements exhibited variation trends consistent with the low-field capacitance and DC current indices. The discrimination among samples with different aging times was enhanced at 0.1 Hz. These results indicated that operating-voltage-relevant broadband impedance measurement provided a rapid sample-level method for evaluating early-stage insulation aging of 10 kV-class XLPE cable samples under operating-voltage-relevant conditions. Full article

Low-frequency impact sound control remains a critical challenge for floating floor systems. Conventional resilient underlayment materials exhibit insufficient damping and are prone to long-term deformation, making stable low-frequency sound insulation difficult to achieve. This study presents the development of a composite floating floor underlayment comprising recycled rubber granules, polymer resin, and quartz sand. Based on the constrained layer damping-inspired (CLD-inspired) perspective, the vibration attenuation and noise reduction mechanism is elucidated, and the material’s physical properties, mechanical behavior, microstructure, and acoustic performance are systematically investigated. The results indicate that excessively large rubber granules aggravate curing shrinkage cracking. Optimal processing characteristics are achieved with a binder content of 20 wt% and a rubber granule size of 50 mesh. Laboratory characterization reveals that, compared with conventional cross-linked polyethylene (XLPE) foam underlayments, the proposed composite underlayment reduces the impact sound pressure level by an average of 3–5 dB in the low-frequency band below 250 Hz, and the overall sound insulation performance is improved by 10.77%. Dynamic mechanical analysis shows the composite storage modulus declines from 280 MPa at −20 °C to 10 MPa at 80 °C, while the loss factor remains above 0.2 under typical indoor conditions. Such stable viscoelastic behavior enables efficient shear dissipation of low-frequency vibration energy under the CLD-inspired mechanism. Full-scale field testing combined with long-term observation over 3000 loading cycles demonstrates excellent structural compatibility between the underlayment and the gypsum screed, with no cracking or appreciable deformation observed during prolonged service. The weighted impact sound improvement index (ΔLw) attains 15 dB. These findings verify that the CLD-inspired composite underlayment simultaneously achieves efficient low-frequency impact sound control and superior long-term structural stability, providing an innovative material solution and design strategy for impact noise mitigation in residential floating floor applications. Full article

To investigate the influence of secondary crosslinking time on the interfacial insulation performance between crosslinked polyethylene (XLPE) and a semiconductive shielding layer, XLPE sheets and semiconductive EVA pellets were selected. XLPE/semiconductive shielding layer interfacial specimens with secondary crosslinking times of 10 min, 15 min, 30 min, 45 min and 60 min were prepared. Polarization and depolarization current (PDC) measurements, breakdown voltage tests, peel adhesion strength evaluation and scanning electron microscopy (SEM) observations were systematically performed. The interfacial polarization current, characteristic breakdown voltage and interfacial peel adhesion strength of the specimens were obtained and analyzed. The experimental results indicate that, with increasing secondary crosslinking time, the interfacial polarization current showed an initial decrease followed by an increase, and the characteristic breakdown voltage and the interfacial peel adhesion strength showed an initial increase followed by a decrease. Further analysis suggests that an excessively long secondary crosslinking time reduces the area of the interfacial interpenetration region between XLPE and the semiconductive shielding layer, which is the primary factor responsible for the deterioration of interfacial insulation performance. The results provide experimental evidence and theoretical support for optimizing flexible joint manufacturing processes and improving their operational reliability and service lifetime. Full article

This study addresses the impact of temperature gradient-induced non-uniform aging on the accuracy of space charge measurements in cross-linked polyethylene (XLPE) insulation for high-voltage direct-current cables. Existing pulse-echo acoustic (PEA) recovery algorithms neglect the evolution of material acoustic and dielectric properties during aging. To overcome this limitation, the systematic degradation of sound velocity, attenuation dispersion, and dielectric constant subjected to temperature gradient aging was experimentally investigated. Specimens were aged at temperatures ranging from 40 to 100 °C for durations up to 49 days. Then, quantitative models describing the dependence of acoustic and dielectric properties on aging severity were established. A space charge signal correction algorithm was then developed, incorporating nonlinear adjustments for sound velocity, attenuation, and permittivity according to the through-thickness aging profile. The algorithm’s accuracy was validated by comparing recovered charge waveforms and electric field distributions under 5 kV/mm for samples aged under different temperature gradients. The application of the method under high-voltage DC conditions revealed that aging induces non-monotonic changes in sound velocity, increased attenuation coefficients, and elevated low-frequency dielectric constants. Temperature gradient aging promotes heteropolar charge accumulation. This work provides a theoretical and methodological basis for improving the accuracy of the insulation condition assessment in long-term service HVDC cables. Full article

In order to explore the effect of pH value of the solution on the growth characteristics of electro-hydro mixed branches of cross-linked polyethylene (XLPE) cables, an electro-hydro mixed branch experimental platform with different pH values was built to accelerate the aging of XLPE cables. The growth characteristics of electro-hydro mixed branches under different pH environments were systematically observed and analyzed by combining macroscopic dielectric properties test with microscopic morphology detection. The macroscopic test results show that the aging degree of the cable is more serious in the acidic or alkaline environment. When there are electrical tree defects in the insulation, acidic or alkaline solutions with different pH values will promote the accelerated aging of mixed branches, and the acceleration effect of acidic environment is more significant. After microscopic detection of sample slices with different acidity and alkalinity, it was found that both acidic and alkaline environments could accelerate the growth of mixed branches. On the basis of electrical trees, the strong acid and strong alkali environment was more suitable for the development of mixed branches than the weak acid and weak alkali environment, and the promotion effect of acidic solution was more prominent. At the same time, this study also deeply analyzed the conversion mechanism of electrical tree to water tree in cables under different pH conditions. Finally, through the correlation analysis between the dielectric performance parameters and the branch density of different groups of samples, the fitting model of the branch density on the macroscopic dielectric performance parameters is obtained by curve fitting, which provides an effective non-destructive testing method for cable multi-branch aging. These results reflect the structure–property relationship of XLPE polymer under acid-base corrosion and electric field coupling and reveal the microstructure degradation mechanism of polyethylene insulation. Full article

Crosslinked polyethylene (XLPE) is a widely used cable insulation material for power cables at various voltage levels, offering excellent electrical, mechanical, and thermal stability. However, during the continuous extrusion moulding process, prolonged shear action and localized temperature accumulation can easily induce premature crosslinking. This leads to a decline in melt rheological properties and reduced processing stability, as well as having an adverse effect on the microstructure and overall performance of the formed insulation layer. This study systematically investigated the impact of shear-induced pre-crosslinking on the mechanical properties and dielectric characteristics of XLPE cable insulation materials through experimental testing methods. The experimental results demonstrate that, while premature crosslinking has a minimal effect on mechanical properties, it significantly deteriorates dielectric performance, as evidenced by increased conduction current, reduced breakdown strength, and compromised microstructural integrity. These findings suggest that, to improve the quality and reliability of XLPE cable production, engineering designs should prioritize controlling the pre-crosslinking process to ensure stable dielectric performance. Full article

This paper explores the correlation between the macroscopic breakdown behavior and microscopic particle motion of cable joint cross-linked polyethylene–silicone rubber (XLPE-SiR) insulation interface breakdown. Firstly, based on the characteristics of Pd values exceeding 1000 Torr·cm at the insulation interface, it shows that XLPE-SiR insulation interface breakdown falls within the scope of streamer discharge. Further, the generation process of the insulation interface breakdown is described through microscopic particle motions, and the microscopic expression of the interface breakdown energy of cable joints is derived. Based on this, it is found that the ionization degree (χ) of the interface breakdown channel is the major microscopic parameter that affects the interface breakdown energy. An experiment was conducted on equivalent samples under different conditions of pyrolysis degree interface pressure (P) and breakdown gap (d). The experiment shows that the value of χ is positively related to the pyrolysis degree and P. Additionally, it is found that with the increase in d, the value of χ increases at first and then decreases gradually. The results of this paper can be taken as a basis for research on the microscopic process of XLPE-SiR insulation interface breakdown at different stages. Full article

Grafted polypropylene (PPG) has demonstrated significant potential as a recyclable insulation material for high-voltage cables. While its fundamental electrical, mechanical and thermal properties have been widely studied, research on its long-term performance remains insufficient. This study comparatively investigates the thermo-oxidative ageing performance of PPG and traditional cross-linked polyethylene (XLPE) to evaluate the expected lifespan of cable insulation. The evolution of mechanical and electrical properties of PPG and XLPE was monitored during accelerated thermo-oxidative ageing experiments conducted at their respective maximum allowable operating temperatures, and the most sensitive ageing parameter was identified. Furthermore, the influence of thickness on the insulation ageing process was examined through experiments on samples of different thicknesses. Results indicate that the estimated thermo-oxidative ageing lifespan of XLPE at its maximum operating temperatures of 90 °C is 37.75 years, while that of PPG at 110 °C is 45.65 years. This work offers a practical methodology for polymer ageing lifespan analysis and provides valuable insights for assessing the long-term performance of PPG cables in high-voltage applications. Full article

As a non-invasive diagnostic technique, evolved gas analysis (EGA) holds significant value in assessing the insulation conditions of critical equipment such as power cables. Current analytical methods face two major challenges: insulation materials may undergo multiple aging mechanisms simultaneously, leading to interfering characteristic gases; and traditional approaches lack the multi-label recognition capability to address concurrent fault patterns when processing mixed-gas data. These limitations hinder the accuracy and comprehensiveness of insulation condition assessment, underscoring the urgent need for intelligent analytical methods. This study proposes a deep convolutional neural network (DCNN)-based multi-label classification framework to accurately identify the gas generation characteristics of five typical power cable insulation materials—ethylene propylene diene monomer (EPDM), ethylene-vinyl acetate copolymer (EVA), silicone rubber (SR), polyamide (PA), and cross-linked polyethylene (XLPE)—under fault conditions. The method leverages concentration data of six characteristic gases (CO₂, C₂H₄, C₂H₆, CH₄, CO, and H₂), integrating modern data analysis and deep learning techniques, including logarithmic transformation, Z-score normalization, multi-scale convolution, residual connections, channel attention mechanisms, and weighted binary cross-entropy loss functions, to enable simultaneous prediction of multiple degradation states or concurrent fault pattern combinations. By constructing a gas dataset covering diverse materials and operating conditions and conducting comparative experiments to validate the proposed DCNN model’s performance, the results demonstrate that the model can effectively learn material-specific gas generation patterns and accurately identify complex label co-occurrence scenarios. This approach provides technical support for improving the accuracy of insulation condition assessment in power cable equipment. Full article

This study examines the use of electronic waste (e-waste) as an alternative material in concrete for sustainability and natural resource conservation. Various e-wastes, such as Polyvinyl Chloride (PVC), Glass-Reinforced Plastic (GRP), Glass Fiber-Reinforced Polymer (GFRP), cross-linked polyethylene (XLPE), polyethylene (PE), electronic cable waste (ECW), Waste Electrical Cable Rubber (WECR), copper fiber (Cu Fib.), aluminum Fibers (Al fib.), steel fibers, basalt fibers, glass fibers, aramid−carbon fibers, Kevlar fibers, jute fibers, and optical fibers, were tested for influence on compressive, flexural, tensile strength, modulus of elasticity, and water absorption. Outcomes show that fine particle waste at low levels (0.2–1.5%) can improve mechanical performance, while higher levels of replacement or coarse particles generally reduce performance. Mechanical and physical properties are highly sensitive to material type, particle size, and dose. Life cycle assessment (LCA) and predictive modeling are recommended as validation for sustainability benefits. Full article

Overhead transmission lines have long relied on cross-linked polyethylene (XLPE) insulation. The production of XLPE insulation requires silane cross-linking, which generates by-products, consumes high energy, and results in poor recyclability-retired XLPE insulation can only be disposed of through incineration or landfilling. Additionally, its high density leads to increased cable weight and sag, reducing the service life of the cables. Therefore, there is an urgent need to develop recyclable and lightweight insulation materials. In this study, recyclable polypropylene (PP) was used as a substitute for XLPE. Hollow glass microspheres (HGM) were incorporated to reduce weight, and hydrogenated styrene-ethylene-butylene-styrene block copolymer (SEBS) was added for toughening, thereby constructing a PP/HGM/SEBS ternary composite system. The results show that the introduction of HGM into the PP matrix effectively reduces the material density, decreasing from 0.890 g/cm³ (pure PP) to 0.757 g/cm³—a reduction of 15%. With the addition of SEBS, the mechanical properties of the composite are significantly improved: the tensile strength increases from 14.94 MPa (PP/HGM) to 32.40 MPa, and the elongation at break jumps sharply from 72.02% to 671.22%, achieving the synergistic optimization of “weight reduction” and “strengthening-toughening”. Electrical performance tests indicate that the PP/HGM/SEBS composite exhibits a volume resistivity of 1.66 × 10¹² Ω·m, a characteristic breakdown strength of 108.6 kV/mm, a low dielectric loss tangent of 2.76 × 10⁻⁴, and a dielectric constant of 2.24. It achieves density reduction while maintaining low dielectric loss and high insulation strength, verifying its feasibility for application in lightweight insulation scenarios of overhead transmission lines. Full article

Crosslinked polyethylene (XLPE) has been the cornerstone material in the power industry for insulating high-voltage cables due to its exceptional properties, including reduced dielectric loss, high dielectric constant and thermal conductivity, and excellent resistance to electrical stress. In the current study, in order to further enhance the electrical and mechanical properties of XLPE’s various types of nanofillers such as metal oxides, boron nitride nanosheets of nanosilica and graphene oxide are incorporated into the XLPE matrix. These nanoparticles promote the occurrence of numerous trap sites, even at modest concentrations, due to their extensive interfacial regions, which affect crucial characteristics including breakdown voltage strength, electrical tree growth, structural defects, space charge accumulation, and thermal aging. The present review summarizes the effects of nanoparticles on the dielectric performance of XLPE. At the same time, the current advancements in the development of a new generation of recyclable insulation materials are briefly discussed. Full article

High-voltage (HV) cable systems—particularly those insulated with cross-linked polyethylene (XLPE)—are increasingly deployed in both AC and DC applications due to their excellent electrical and mechanical performance. However, their long-term reliability is challenged by partial discharges (PD), insulation aging, space charge accumulation, and thermal and electrical stresses. This review provides a comprehensive survey of the state-of-the-art technologies and methodologies across several domains critical to the assessment and enhancement of cable reliability. It covers advanced condition monitoring (CM) techniques, including sensor-based PD detection, signal acquisition, and denoising methods. Aging mechanisms under various stressors and lifetime estimation approaches are analyzed, along with fault detection and localization strategies using time-domain, frequency-domain, and hybrid methods. Physics-based and data-driven models for PD behavior and space charge dynamics are discussed, particularly under DC conditions. The article also reviews the application of numerical tools such as FEM for thermal and field stress analysis. A dedicated focus is given to machine learning (ML) and deep learning (DL) models for fault classification and predictive maintenance. Furthermore, standards, testing protocols, and practical issues in sensor deployment and calibration are summarized. The review concludes by evaluating intelligent maintenance approaches—including condition-based and predictive strategies—framed within real-world asset management contexts. The paper aims to bridge theoretical developments with field-level implementation challenges, offering a roadmap for future research and practical deployment in resilient and smart power grids. This review highlights a clear gap in fully integrated AC/DC diagnostic and aging analyses for XLPE cables. We emphasize the need for unified physics-based and ML-driven frameworks to address HVDC space-charge effects and multi-stress degradation. These insights provide concise guidance for advancing reliable and scalable cable assessment. Full article

Crosslinked polyethylene (XLPE) is a widely used material which—unlike polyethylene—is very stable both chemically and mechanically. Therefore, waste from this material is difficult to process. A very promising way is slow pyrolysis catalyzed by FeTiO₃ (ilmenite), which allows the conversion of this waste into hydrocarbons via degradation of the rigid chemical structure of crosslinked material. High liquid hydrocarbon yields were achieved by slow pyrolysis both without and with a catalyst at a final temperature of 470 °C (65 and 75–76 wt.%, respectively), but with the catalyst significantly changing the composition of the resulting hydrocarbons. To reveal the possibilities of using the FeTiO₃ catalyst for processing waste XLPE, the effect of this catalyst on the degradation of the XLPE structure was investigated. The degradation is probably greatly facilitated by the action of the FeTiO₃ catalyst at the defect sites of the XLPE structure, i.e., at the tertiary carbons in the main chain where branching into cross-links occurs. In this way, the FeTiO₃ catalyst, even in very small amounts (1%), significantly promotes the degradation of the XLPE structure. This leads to the formation of liquid hydrocarbons, up to 92 wt.% of the products obtained. The novelty of this work lies in a technologically feasible method for processing resistant crosslinked waste material using an inexpensive catalyst; the proposed method provides hydrocarbons with high utility value. On the whole, slow pyrolysis of XLPE waste catalyzed by FeTiO₃ at a final temperature of 470 °C and carried out under well-defined conditions appears to be a promising method for converting this waste into valuable hydrocarbons and energy gas. Full article

Reliable DC cable insulation is crucial for photovoltaic (PV) systems and high-voltage DC (HVDC) networks. However, conventional materials such as cross-linked polyethylene (XLPE) and polyvinyl chloride (PVC) face challenges under prolonged DC stress—notably space charge buildup, dielectric losses, and thermal aging. Cross-linked polyolefin (XLPO) has emerged as a halogen-free, thermally stable alternative, but its comparative DC performance remains underreported. Methods: We evaluated the insulations of virgin XLPO, XLPE, and PVC PV cables under ±1 kV DC using time-domain indices (IR, DAR, PI, Loss Index), supported by MATLAB and FTIR. Multi-layer cable geometries were modeled in MATLAB to simulate radial electric field distribution, and Fourier-transform infrared (FTIR) spectroscopy was employed to reveal polymer chemistry and functional groups. Results: XLPO exhibited an IR on the order of 10⁸–10⁹ Ω, and XLPE (IR ~ 10⁸ Ω) and PVC (IR ~ 10⁷ Ω, LI ≥ 1) at 60 s, with favorable polarization indices under both polarities. Notably, they showed high insulation resistance and low-to-moderate loss indices (≈1.3–1.5) under both polarities, indicating controlled relaxation with limited conduction contribution. XLPE showed good initial insulation resistance but revealed polarity-dependent relaxation and higher loss (especially under positive bias) due to trap-forming cross-linking byproducts. PVC had the lowest resistance (GΩ-range) and near-unit DAR/PI, dominated by leakage conduction and dielectric losses. Simulations confirmed a uniform electric field in XLPO insulation with no polarity asymmetry, while FTIR spectra linked XLPO’s low polarity and PVC’s chlorine content to their electrical behavior. Conclusions: XLPO outperforms XLPE and PVC in resisting DC leakage, charge trapping, and thermal stress, underscoring its suitability for long-term PV and HVDC applications. This study provides a comprehensive structure–property understanding to guide the selection of advanced, polarity-resilient cable insulation materials. Full article