As a critical insulating dielectric in high-voltage direct current transmission equipment, the comprehensive performance of polypropylene film has an important impact on the operational reliability and service life of power electronic devices. Therefore, it is urgent to establish a quantifiable and comparable comprehensive evaluation method. In this paper, a comprehensive performance evaluation index system of polypropylene film was constructed, and a comprehensive evaluation method combining combination weighting and extension cloud model was proposed. First, the subjective weights of indicators were determined by using the extension analytic hierarchy process, and the subjective weights were obtained by improved entropy weight method. On this basis, the optimization integration of subjective and objective weights were achieved through game theory. Subsequently, the extension cloud model was introduced to calculate the cloud correlation degree to complete the comprehensive performance grade determination of films, and the credibility of the evaluation results was tested in combination with the confidence factor. Finally, the reliability of the model was verified by objective performance characterization experiments. The results show that this method can achieve the grading of comprehensive properties of polypropylene films, and the evaluation results are in good agreement with the test conclusions regarding insulation, mechanical properties, and self-healing performance. The proposed comprehensive evaluation model is scientific and practical, which can provide an effective theoretical basis for the performance evaluation and material optimization design of polypropylene film.

After long-term outdoor operation, composite insulators undergo ageing, resulting in a decrease in their anti-pollution performance. Insulation cleaning as a repair measure is an important means to restore its performance. To assess the feasibility of insulation cleaning agents for ageing composite insulators, this paper used the method combining mi-crostructure, group changes, and electrical performance to study the effects of different insulation cleaning agent amounts and thermal ageing duration on their insulation recovery characteristics. The results show that the cleaning agent in slightly wet state can optimize the surface structure of the artificial accelerated ageing composite insulator (operated for 3 years) and improve its hydrophobicity and electrical performance. However, under the action of the cleaning agent in fully wet state, due to prolonged swelling effect, the number of surface cracks on composite insulators increases and their depth deepens, making their hydrophobicity and electrical performance decrease slightly. Under the action of insulation cleaning agent, the severely aged composite insulators after 10 years of operation will expose the internal matrix with lighter ageing, but under the fully wetting state, the pulverization layer will be peel off and the deep cracks will be exposed significantly, indicating that excessive cleaning will increase the operation hidden danger of long-term aged insulators. With the extension of ageing time, the improvement effect of the cleaning agent in slightly wet state on the artificial accelerated aging composite insulator sample weakens, while the cleaning agent in fully wet state will accelerate the loss of the components of composite insulator.

Dust-like metal particles are commonly found inside the cavity of GIS that has been operated for many years. However, there is still no clear conclusion as to whether the metal dust will cause partial discharge (PD) and thereby pose a threat to the GIS insulation. In this study, five measurement techniques including photon counting, optical intensity, UHF, ultrasonic, and pulse current methods were employed to investigate the PD characteristics of metal dust with different particle sizes and unit area concentrations under AC voltage. The adaptability of different measurement methods to the measurement of local discharge signals induced by dust particles was clarified, and the mechanism of discharge voltage reduction for insulating gas caused by dust accumulation was preliminarily examined. The results show that compared to optical methods, UHF, ultrasonic, and pulse current methods show lower sensitivity to PD signals generated by metal dust. The number of photons generated by metal dustincreases with the increase of unit area concentration and electrical field strength, and the amplitude of PD optical intensity signals shows a positive correlation with the particle size of dust. Furthermore, the accumulation of metal dust will to some extent reduce the insulation performance of the gas gap in GIS.

Aiming at the problem that the anti-corona structure of newly replaced stator bars is different from that of original factory stator bars when the stator bar is partially replaced in the stator winding accident handling for large hydro-generators, this paper employed the finite element simulation software to simulate and analyze the electric field distribution at the winding ends of the stator bars with two kinds of anti-corona structures under mixed use conditions, and calculate the distribution laws of potential and electric field intensity at the ends. A wingding model was constructed based on two kinds of stator bars, and the theoretical analysis results were verified by corona test. The results show that under the 1.1U_N assessment voltage, the electric field intensity at the end of the stator winding with a mixed use of the bars with two kinds of anti-corona structures meets the requirements of relevant standards, and there is no abnormal corona risk. The test further confirms that the mixed use of the stator bars with two kinds of anti-corona structures can effectively avoid corona corrosion at the end. This study verifies the feasibility of the mixed use of newly developed anti-corona structure bars and original factory bars, providing reliable technical support for the partial replacement of stator windings in large hydro-generators.

On the basis of the film-making data of the 300 mm wide polyimide casting test line and the 1 200 mm wide polyimide biaxial stretching production line of Guilin Electrical Research Institute Co., Ltd., the effects of formulation, equipment, process, and other factors on the preparation of high thermal conductivity insulating polyimide films were investigated. The results show that compared with the biaxial stretching method, the casting method has advantages such as low trimming loss, simple equipment and process, excellent film-forming properties, lower cost, and good thermal conductivity of prepared films. In terms of improving the thermal conductivity of thermal conductive films, it is necessary to overcome the problems such as difficulty in peeling the casting film from steel belt, increased difficulty in filler dispersion, poor interfacial matching between filler and resin, and decreased film-forming continuity when boron nitride is highly filled.

In this paper, corona-resistant enamelled round wires were selected as test objects, different twisted wire samples were prepared, and the effects of the sample pitch, the load applied to the wire pair, and number of twists on their corona resistant life were investigated. The results show that a longer twist pitch may lead to shorter failure time, while increasing the load will significantly extend the failure time of the sample, and the effect of different number of twists on failure time of the sample is not obvious. After being soaking in sodium chloride solution, the failure time of the sample slightly extended. However, as the concentration of the solution further increases, the change in failure time is relatively small. After the steel ball used for clamp the sample conductor is subjected to long term corrosion, during the corona resistance test, the exposed conductors of the sample will exhibit more severe electrochemical corrosion characteristics, resulting in a significant increase in the right-skewed extreme value in the failure time data. Based on the above research, when preparing twisted wire samples of enamelled round wires, the twist pitch and load should be precisely controlled, and the steel balls should be regularly replaced according to the testing frequency, to ensure the consistency of corona-resistant test results.

Under the "dual carbon" goals, traditional epoxy resins, which are depend on petrochemical feedstocks and are non-recyclable, have severely hindered the current transformation of power systems. Developing low-carbon and environmental friendly epoxy resins has become a research focus. This study adopted a “rigidity-flexibility” balancing strategy to prepare a bio-based epoxy resin with Schiff base dynamic covalent bonds cured directly by an aldehyde-terminated bio-based epoxy crosslinker and a diamine. Its mechanical properties, insulation performance, and property changes before and after multiple recycling processes were investigated. The results show that the novel epoxy resin achieves a tensile strength of 70.1 MPa and an electric strength of 130 kV/mm. This dynamically cross-linked epoxy resin can be effectively reprocessed and recycled via solvent, retaining a tensile strength of 58.8 MPa and an electric strength of 111 kV/mm after multiple reprocessing cycles.

The environmental impact of greenhouse gases has garnered widespread global attention, and the low-carbon transformation of power equipment is of great significance for achieving the carbon peaking and carbon neutrality goals. Based on the life cycle assessment (LCA) method, we focused on the raw material acquisition, product manufacturing, and waste disposal stages of an 800 kVA epoxy cast dry-type transformer, and evaluated its carbon footprint and environmental impact from a material perspective. The Monte Carlo simulation method based on the triangular distribution and Sobol sequence was adopted to conduct uncertainty analysis on the carbon footprint results, so as to assess the uncertainty of carbon emissions from key resources. Based on two environmental impact assessment methods CML-IA baseline 2001 and ReCiPe 2016, the environmental impact degree of transformer at each stage was comprehensively evaluated. The results show that the total carbon footprint of the transformer is 8 996.25 kgCO₂e, with the raw material acquisition stage contributing the most to the product carbon footprint, reaching 7 186.51 kgCO₂e. Copper, silicon steel sheets, and epoxy resin are the main carbon sources, accounting for 42.87%, 31.17%, and 23.93%, respectively. Both sensitivity analysis methods are consistent with the actual situation, but the 95% confidence interval obtained by the Sobol sequence method is significantly wider than the [8 691.92, 9 311.68] kgCO₂e of the triangular distribution, demonstrating a more sufficient ability to express uncertainty. The first-order sensitivity indices of the two key resources, epoxy resin and power consumption, calculated by the two methods are 0.460 and 0.499, respectively, indicating that they have the most obvious impact on the carbon footprint of the transformer. The environmental impact assessment results of CML-IA baseline 2001 and ReCipe 2016 show that the raw material acquisition stage dominates all environmental damage categories, with the most significant impact on marine ecotoxicity. The core causes are the heavy metal emissions during the mining and processing of copper and silicon steel sheets, as well as the organic pollutants released during the synthesis of epoxy resin.

This study aims to prepare high-performance polypropylene (PP) insulation materials and investigate the enhancement mechanism of their properties. By combining in-reactor alloying and blending modification technologies, PP insulation materials with elastomer mass fractions of 20% to 30% for high-voltage cables were prepared. The interfacial compatibility between the elastomer and PP matrix and its impact on the performance of the PP insulation material were studied. The results show that the propylene-based elastomer can effectively improve the interfacial compatibility between elastomers and PP matrix, thereby reducing interfacial defects. The "bimodal" particle size distribution design of elastomers successfully balances the dual effects of the elastomer on mechanical toughness and electrical strength of PP insulaton materials, realizing the synergistic improvement in mechanical toughness, electric strength, and thermal stability, demonstrating excellent overall performance. Moreover, the prepared PP cable material possesses good processing adaptability.

This study systematically investigated the effect of the type and content of ethylene-butyl acrylate (EBA) copolymer on the properties of linear low-density polyethylene (LLDPE)-based non-crosslinked semiconductive shielding materials. A series of shielding material samples were prepared, and their physicochemical properties, volume resistivity, and mechanical performance were characterized. The results show that the incorporation of EBA significantly improves the processability and electrical conductivity of the shielding material. When the mass fraction of EBA in the matrix resin increases from 0 to 15%, the melt flow index of the shielding materila increases from 0.95 g/10 min to 1.15 g/10 min, while the volume resistivity decreases from 11.68 Ω·cm to 8.69 Ω·cm. However, the addition of EBA also leads to reduction in crystallinity and mechanical properties of the shielding material. Among the samples modified by different types of EBA, the 35BA40-modified sample exhibits optimal electrical conductivity and processing flowability, whereas the E2770-modified sample shows superior mechanical performance.