单宁酸-钠涂层法界面改性对光纤复合绝缘芯体电气及界面性能的影响OA

The rapid advancement of ultra-high voltage direct current(UHVDC)transmission technology has placed higher demands on the sampling accuracy and response speed of measurement equipment.Optical current transformers(OCTs)are widely used due to their high insulation,fast response,and electromagnetic interference resistance.As a key structural component,fiber-optic composite insulators serve the dual functions of information transmission and electrical insulation.However,the multi-dielectric interface between the optical fiber and the core material—typically low smoke zero halogen polyethylene(LSZHPE)and syntactic foams(SF)—is prone to defects that can lead to internal discharge or fiber breakage.This study addresses these reliability issues by proposing an interfacial modification strategy using a tannic acid-sodium(TA-Na+)coating method.By introducing active functional groups such as phenolic hydroxyl groups,this green and efficient method aims to achieve synergistic optimization of mechanical and electrical performance at the fiber-to-core interface. The investigation combined molecular dynamics simulations with experimental verification to evaluate the effectiveness of the TA-Na+coating.Molecular dynamics simulations were performed using Materials Studio software to calculate surface energy and interfacial binding energy under varying coating coverage levels.For the experimental phase,LSZHPE fibers were ultrasonically cleaned and immersed in TA-Na+solutions with concentrations of 1,2,and 3 mg/L for durations of 1,2,or 3 hours.These modified fibers were then embedded in an epoxy-based SF matrix composed of E-51 epoxy resin,methylhexahydrophthalic anhydride hardener,and polymethyl methacrylate hollow microspheres.The modified fibers were characterized using scanning electron microscopy and atomic force microscopy for surface morphology,while Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy were employed to analyze chemical structures and elemental compositions.System performance was further assessed through breakdown strength tests,micro-bond tests for interfacial shear strength(IFSS),and water diffusion leakage current measurements. Molecular dynamics simulations indicated that TA-Na+coatings significantly enhance surface energy,showing a 172.98%increase at 100%coverage due to the introduction of strong polar functional groups.Experimental characterization confirmed that tannic acid successfully attached to the fiber surface,with X-ray photoelectron spectroscopy identifying the chelation of tannic acid with sodium ions to form a stable three-dimensional network.Results demonstrate that low concentrations of TA-Na+combined with longer treatment times produce the most uniform and stable coatings.The breakdown strength of modified samples reached a maximum of 14.266 kV/mm,representing an 8.57%improvement over unmodified cores.Interfacial performance showed substantial gains,with the maximum IFSS rising by 112.84%.Additionally,the water diffusion leakage current fell to a minimum of 54.09 μA.Conversely,excessive concentrations or treatment times led to coating cracks and deposits that degraded performance by causing electric field distortion.Ultimately,the TA-Na+coating method proves to be a simple and efficient strategy for mitigating interface defects in fiber-optic composite insulators.