Guochang Li

Silicone rubber (SiR) exhibits excellent electrical, mechanical and antifouling properties, and is widely used in power equipment, such as insulators and cable accessories. With the increasing popularity of high‐voltage and high‐power equipment, higher requirements have been imposed on the thermal conductivity and insulation performance of SiR. In this study, a multidimensional particle composite strategy was proposed to enhance the thermal conductivity of SiR, and the influence of various particle forms on its electrical insulation performance was thoroughly investigated. The results showed that 180 phr by mass of Al ₂ O ₃ increased the thermal conductivity and breakdown strength of the composite material compared to pure SiR by 317.3% and 64.8%, respectively. Introducing 15 phr by mass of BNNs into the aforementioned composite material further increased the thermal conductivity and breakdown strength by 23% and 24.4%, respectively. Through simulation calculations of FFV and MSD, this study revealed the regulatory mechanism of multi‐shaped inorganic fillers on the insulation performance of SiR, achieving simultaneous improvement of heat dissipation and insulation performance, and providing theoretical support for the engineering application of such composite materials in electrical equipment.

Polypropylene (PP) composites possess excellent electrical insulation and have become a new trend in the development of power cable insulation. The stability of the molecular chain directly determines the service life of power equipment. Therefore, it is essential to investigate the thermal aging behavior of the styrene ethylene butylene styrene (SEBS) modified PP cable insulation. In this paper, the independent aging mechanisms of each component in systems are studied using a multi‐scale evaluation method. The experimental results show that with the progression of aging, the mechanical and electrical properties of the composite decrease significantly. The simulation results indicate that the activation energies for hydrogen dissociation of SEBS are 339.08 and 362.19 kJ/mol, respectively, both lower than that of pure PP (374.65 kJ/mol). Furthermore, oxygen is more likely to penetrate and participate in the thermal oxidative aging reaction of the molecular chains in the PP/SEBS composites. This induces molecular chain scission and the generation of oxygen‐containing functional groups, which in turn alters the material structure and results in the degradation of macroscopic electrical properties. This work provides significant guidance for the research on thermal aging control of PP/SEBS composites.

Under high electric field strength, the charge transport within PP dielectric will generate a Coulomb potential field, which significantly affects the dielectric polarization process. There is an intrinsic connection between charge accumulation and the degradation of dielectric constant. In this paper, the influence relationship of the charge transport process on dielectric properties was studied. Firstly, a bipolar carrier transport‐polarization correlation model under high electric field was established to calculate the effect of space charge on the dielectric properties of PP. Under low fields, charges mainly accumulate near PP electrodes, while under high fields, charges migrate to the dielectric center, inducing significant electric field distortion. Local space charge accumulation leads to a notable decrease in dielectric constant. A capacitor model was further built based on the above model to study the effects of space charge on the electric field distribution and dielectric constant of the capacitor. Electric field distortion in the capacitor is mainly concentrated at electrode edges. When space charge density reaches 30 C/m ³ , the effective electric field decreases by 6.75 kV/mm, and the dielectric constant drops to 95% of its initial value. Finally, the mechanism underlying the reduction in dielectric constant induced by space charge‐regulated polarization was clarified.

Polypropylene (PP) is currently the most promising polymer material used in cable insulation, because of its excellent electrical insulation properties and heat resistance. Now, the dynamic changes in composition and properties of multi‐component composites with PP are being studied. In this paper, maleic anhydride grafted polypropylene (MAH‐g‐PP) is used as a compatibilizer to modify the comprehensive properties of PP/SEBS, particularly the mechanical and electrical properties. The method of mutual verification between experiments and simulations is adopted. The elongation at break of the composites decreases slightly. The low‐frequency permittivity increases gradually, and the high frequency is basically maintained at 2.32. The breakdown strength increases first and then decreases, and the composite with 3.5 wt% MAH‐g‐PP content is the highest, 148.14 kV/mm, an increase of 46.12% compared with PP/SEBS. The MS results show that the E _int absolute value of SEBS to MAH‐g‐PP is 6.29 times of SEBS and PP, being −313.08 kcal/mol. In addition, the band gap of MAH‐g‐PP is the narrowest, at 4.06 eV, but there are two distinct localized energy levels, which hindered the transport of charge carriers. This work has significant promoting significance for the application of new environmentally friendly polypropylene cables.

The traditional stress detection methods for electrical equipment are mainly achieved through mechanical or electrical sensing technologies, which face drawbacks such as electromagnetic interference (EMI), muting sensitivity, and potential insulation damage of the equipment itself. In this work, a flexible thin composite material with excellent mechanical luminescence properties and insulation performance is proposed, which can be used for mechanical stress monitoring of power equipment and can also indirectly achieve damage warning. Its advantage lies in visually reflecting stress variations through a visualization mechanism, while the sensing material itself maintains excellent insulation properties, avoiding damage to the original insulation caused by the embedded sensors. Elastomeric composite materials capable of exhibiting mechanoluminescence are prepared by blending SrAl2O4:Eu²⁺Dy³⁺ (SAOED) particles with ethylene propylene diene monomer (EPDM) rubber at different mass ratios. The effects of SAOED particle content on the luminescence, mechanical and electrical properties of the composites are investigated. The mechanoluminescence performance demonstrate that the elastomeric composite with 40% SAOED particle exhibits superior mechanoluminescence properties and maintains excellent electrical insulation performance. The stress required for the mechanoluminescence is 0.96 MPa, which is easier to produce luminescence than the composite material with 25% SAOED content. The mechanoluminescence intensity of the composite material with 40% SAOED content is 37.4% higher than that of the composite material with 25% SAOED content. The electrical performance shows that the volume resistivity is 8.711×10¹¹ Ω·m at power frequency. The breakdown strength is 92.51 kV/mm that it can meet the insulation requirements of power equipment. Finally, the luminescence mechanism of the composite is further analyzed using the carrier detrapping band model. This work provides a novel idea for the development of intelligent sensing for stress detection of power equipment and has broad potential application prospects.

Polypropylene (PP) is widely used in high‐voltage capacitors due to its advantages in insulation performance, processability, degradability, and recyclability. During long‐term operation, space charges are easily injected from electrodes into the dielectric under a strong electric field, inducing material degradation and even breakdown. Space charge suppression has long been a key issue in engineering applications. Different from the traditional technology route of space charge suppression by nano‐doping, a kind of novel physical method of regulating the charge migration path inside the dielectric by Strontium ferrite Magnetic Nanoparticles (SrFe ₁₂ O ₁₉ ) was proposed. The experimental results show that the oriented magnetic field generated by SrFe ₁₂ O ₁₉ can inhibit the free charge movement, reduce leakage current, and improve breakdown strength. Furtherly, PP/SrFe ₁₂ O ₁₉ composite was used as a functional layer to suppress carrier injection, a three‐layer structure (referred to as SPS) was constructed. When the mass fraction of SrFe ₁₂ O ₁₉ is 0.5%, the breakdown strength of the SPS rises to 283 kV/mm, which is 36 kV/mm higher than that of the PP. The leakage current at 100 kV/mm is 2.17 × 10 ⁻⁹ A, decreasing about 81.8%. This work provides a new idea to solve space charge accumulation and improve the breakdown strength of DC capacitors.

High-voltage cables and accessories are the key components of power transmission, and the insulation interface is the weakest part of the insulation system. In order to study the effect of interface defects on the interface discharge characteristics of cables and accessories, firstly, the cross-linked polyethylene (XLPE), silicone rubber (SIR) and semi-conductive (SEMI) samples are prepared, and the composite samples are fabricated (including XLPE/SIR and XLPE/SEMI composite samples). Secondly, the effects of interface defects on the breakdown, dielectric and interface discharge properties of composite samples are analyzed. Finally, the composite interface defect model of cable and accessories is established to calculate the electric field distortion caused by the defect. The results show that the breakdown strength and interface discharge voltage of XLPE/SIR interface with voids and semi-conductive defects are 36.7, 39.98 kV/mm and 12.07, 10.95 kV, respectively. The relative dielectric constant of the samples with defects increased significantly comparing with the samples without defects. The breakdown strength of XLPE/SEMI interface with void, metal and semi-conductive defect are 65.00, 72.79 and 75.23 kV/mm, respectively, and the existence of defect leads to the overall increase of relative dielectric constant. The simulation results show that the maximum electric field distortion caused by voids and semi-conductive defects in XLPE/SIR interface are 19.28 and 10.78 kV/mm, respectively, increasing by 155.70% and 42.97%. The maximum electric field distortion caused by voids, metal and semi-conductivity defects in the XLPE/SEMI interface are 19.09, 8.62 and 8.40 kV/mm, respectively, increasing by 186.21%, 29.24% and 25.94%. The simulation results of electric field distortion are consistent with the breakdown test. This study is helpful to understand the effect of interface defects of cable accessories on electric field distribution, and it can provide reference for the operation, maintenance and fault analysis of cable accessories.