Effect Of Size Factor Of Inorganic Filler On The Electrical Properties Of Polyethylene Composite Dielectric

With the increase of the transmission voltage level of China's power system,the requirements for the insulation characteristics of power cables are getting higher and higher.Polyethylene?PE?is a common material for power cable insulation.In order to improve the performance of power cables to ensure the safe operation of transmission systems,it is important to optimize the electrical properties of polyethylene materials.In this paper,polyethylene was used as the matrix material,MgO and TiO₂ were used as inorganic filler.The effect of the type of inorganic filler,the content of inorganic filler and size factor of inorganic filler on the microstructure and electrical properties of polyethylene composite dielectric were systematically studied.Among them,MgO nanosheets?MgO Sheets?were prepared by hydrothermal method.The effect of MgO nanosheets and MgO particles?MgO NPs?on the electrical properties of polyethylene composite dielectric were compared.The TiO₂ nanofibers?TiO₂ NFs?were prepared by electrospinning technique.The effect of TiO₂ NFs and TiO₂ particles?TiO₂ NPs?on the electrical properties of polyethylene composite dielectric were compared;in order to improve the interfacial compatibility between inorganic filler and matrix,the inorganic was surface modified by silane coupling agent KH-550 before preparing composite dielectric.The composite dielectrics of different mass fractions were prepared by melt blending.At the same time,a group of inorganic filler polyethylene composite dielectric modified without silane coupling agent KH-550 was prepared to study the modification of silane coupling agent KH-550.The XRD,SEM and FTIR were used to characterize the microstructure of the composite dielectric.The dielectric properties,breakdown properties and space charge performance of the composite were studied by electrical testing system.The research results show that the modification of the surface of the inorganic filler by the silane coupling agent can improve the compatibility with the polyethylene matrix and uniformity of dispersion,thereby reducing the dielectric loss,and improving the electrical breakdown field strength of the polyethylene composite dielectric.When the content of MgO NPs and MgO sheets is 0.5 wt.%,1 wt.%,the electrical breakdown field strength of the composite dielectric is higher than that of pure LDPE.When the content of TiO₂ NFs is 0.5 wt.%,the electrical breakdown field strength of the composite dielectric is higher than that of pure LDPE.And as the content of TiO₂ increases,the electrical breakdown field strength decreases.The doping of MgO and TiO₂ can suppress the space charge,and the inhibition effect is better in 1 wt.%MgO NPs/LDPE,1 wt.%MgO Sheets/LDPE,and 0.5 wt.%TiO₂NFs/LDPE composite dielectric.