The strain-hardening geopolymer composite (SHGC) is a new type of fiber concrete with excellent ductility and environmental friendliness. However, the high cost of fibers greatly limits its widespread application. This paper proposes the use of untreated low-cost polyvinyl alcohol (PVA) fibers and polyethylene (PE) fibers to develop a low-cost, high-performance SHGC. Axial compression and axial tension tests were conducted on the SHGC with different PE fiber volume fractions (1%, 1.5%, and 2%) and different PVA fiber replacement ratios (0%, 25%, 50%, 75%, and 100%) to investigate the hybrid effects of fibers with different surface properties and to reveal the mechanism of fiber hybridization on the mechanical behavior of SHGCs. The results show that increasing the PE fiber volume fraction improves the compressive and tensile ductility of the SHGC while increasing the PVA fiber replacement rate impacts the strength indicators positively due to the good interface effect formed between its hydrophilic surface and the matrix. When the PVA fiber replacement ratio is 100%, the compressive strength (93.4 MPa) of the SHGC is the highest, with a 21.1% increase compared to the control group. However, the tensile strength shows a trend of first increasing and then decreasing with the increase in the PVA fiber replacement ratio, reaching the highest at a 25% replacement ratio, with a 12.5% increase compared to the control group. Furthermore, a comprehensive analysis of the economic and environmental performance of the SHGC indicates that a 25% PVA fiber replacement ratio results in the best overall economic benefits and relatively low actual costs, although the effect of fiber hybridization on carbon emission indicators is not significant. This paper provides new ideas and a theoretical basis for designing low-cost SHGCs.

Overhead transmission lines are crucial components of power grid construction, and their carbon emissions significantly impact the low-carbon construction of the power grid. This study adopts a cradle-to-gate life cycle assessment (LCA) method, defining the system boundary as the material production, transportation, and construction phases. Using the carbon-accounting software eFootprint and the emission factor method, we calculate and analyze the carbon emissions of a 500 kV double-circuit overhead transmission line project in Shantou, Guangdong Province, and systematically examine the emission characteristics from material production through construction. Results show that the material production phase dominates the carbon emissions of the project, accounting for 99.82% of the total emissions. Among them, conductors (49.41%) and tower materials (37.28%) are the core sources of carbon emissions, with a combined contribution of 86.69%. The findings highlight conductors and towers as key targets for emission reduction through strategies such as optimized material selection, adoption of high-strength lightweight alternatives, and modular construction techniques. However, this analysis has limitations: it is confined to a single subtropical coastal project, relies on industry-average emission factors from the CLCD database (with inherent methodological uncertainties), excludes operational and end-of-life phases, and should not be generalized without regional validation. While the study identifies key emission hotspots and potential mitigation levers, quantitative low-carbon design guidance requires project-specific data and full life-cycle assessment.

This study investigates the seismic performance of the V3.0 220 kV standard-designed substation of the Southern Power Grid, located in a high-intensity seismic zone, with a focus on the application of seismic isolation technology. Seismic isolation and structural analysis were conducted and shaking table tests were performed on both isolated and non-isolated structural models. A total of 40 tests were carried out using three levels of ground motion intensity (i.e., 140 gal, 400 gal, and 800 gal) and in three directions (unidirectional, bidirectional, and triaxial). The dynamic characteristics, seismic response, and isolation effectiveness were evaluated. Results indicate that the test models exhibit strong agreement with theoretical and numerical predictions, with an average frequency deviation of 10.98%. The fundamental period of the isolated structure was extended by a factor of 2.33 compared to the non-isolated configuration. As the peak ground acceleration increased, structural frequency decreased, and the period increased. The isolated structure showed a lower first-period growth rate (4.82%) than the non-isolated structure (15.38%). Even under 800 gal excitations, the isolated structure remained within the elastic range. Seismic isolation significantly reduced structural response, with a control effectiveness exceeding 50%, enabling a one-degree reduction in seismic design intensity. A vulnerability analysis based on 200 simulated earthquake cases revealed that the isolated structure exhibited lower failure probabilities across four performance states. At 600 gal PGA, the failure probability in the LS3 state was reduced by 27.8%. These findings confirm the effectiveness and reliability of seismic isolation design for substations in high seismic intensity regions.

In order to enhance the energy-dissipation capacity and comprehensive seismic mechanical behavior of prefabricated steel–concrete-composite shear-wall structures, a new prefabricated composite energy-dissipation shear-wall system is proposed, which is composed of a shear-wall module and an energy-dissipation module connected by high-strength bolts. Four sets of comparative mechanical performance testing were conducted on the proposed composite energy-dissipation shear wall, including one set of traditional prefabricated composite shear-wall specimens (specimen TPCW) and three sets of composite energy-dissipation shear-wall specimens designed with different energy-dissipation modules (specimens PCEDW-A, PCEDW-B, and PCEDW-C). The results indicate that the proposed specimens PCEDW-A and PCEDW-B have a good bearing capacity and energy-dissipation characteristics, in which the number and range of concrete crack developments are lower than those of the traditional TPCW specimen under the same loading drift ratio condition. Compared with specimen TPCW, the ultimate bearing capacities of specimens PCEDW-A and PCEDW-B are increased by 13.76% and 17.15%, respectively. However, the equivalent damping ratio of specimen PCEDW-A is much higher than that of specimen PCEDW-B, and the former is nearly four times higher than the latter at the drift ratio of 1/100. Taking into account the load-bearing capacity and energy-dissipation characteristics, using a horizontal diamond-shaped perforated metal damper, specimen PCEDW-A exhibits the optimal mechanical behavior.

Comprehending charge injection at the metal/epoxy interface is essential for designing and applying high-voltage electrical equipment. This study investigates surface charge accumulation in insulators used in high-voltage direct current (HVDC) gas-insulated switchgear (GIS), with a specific focus on the charge injection behavior at the metal/epoxy interface employing first-principles calculations. In this paper, two amine curing agents were selected to construct interface models of a Cu(111) slab and epoxy resin, with repeating fragments representing the crosslinked structure of the resin. Key parameters, including injection barriers, charge transfer, and vacuum energy level shifts (Δ), were evaluated. Notably, molecular structures containing -C₂F₆ bonds exhibited higher electron and hole injection barriers compared to those with -CH₂. Specifically, DDM induces reduced interfacial charge injection barriers and enhanced charge transport capabilities attributed to its low electronegativity and compact spatial configuration, whereas 6FDAM yields elevated barrier heights stemming from its strong electronegative character. The reliability of these findings was further validated through macroscopic charge injection experiments. The above study holds certain referential value for the development and application of high-voltage DC GIS equipment.

Driven by global carbon neutrality targets, the low-carbon transformation of power systems necessitates rigorous carbon evaluation of grid infrastructure. However, existing assessments of overhead transmission lines often exhibit incomplete life-cycle boundaries and lack a coordinated approach to subjective and objective weight allocation. To address these gaps, this study targets overhead transmission lines and constructs a comprehensive low-carbon evaluation index system comprising 14 indicators across four life-cycle stages, namely design, construction, operation, and recycling. A hybrid evaluation model is proposed based on the combined analytic hierarchy process and entropy weighting method. The analytic hierarchy process is utilized to derive expert-based subjective weights, while the entropy weighting method extracts objective data variations from multiple samples, which are then integrated to obtain robust composite weights. An empirical analysis conducted on a 500 kV double-circuit overhead transmission line project in China validates the proposed framework. The results reveal a comprehensive evaluation score of 80.219, corresponding to a “low-carbon” grade. Moreover, the line loss rate (0.234227), operational carbon emissions (0.133978), and steel consumption per unit length (0.122381) are identified as the pivotal indicators dominating the evaluation outcome. This research provides quantitative support and practical criteria for decision-making regarding low-carbon design, green construction, operational loss reduction, and resource-oriented retirement of transmission line projects.