Study On Breakdown And Conductivity Characteristics Of H-BN And ZnO Co-doped EPDM Composite Dielectrics

For the breakdown of the cable accessories in high-voltage direct current(HVDC)due to the uneven distribution of conductivity,this paper is modified by EPDM to form a good match between the electrical conductivity and the main insulation of the cable.Solve the problem of local electric field distribution concentration caused by the conductance gradient.Firstly,zinc oxide(ZnO)particles were doped into the EPDM polymer matrix.The breakdown and conductivity behavior of the composite dielectric after doping were studied by adjusting the different doping ratio systems of ZnO.It is found that with the increase of the amount of zinc oxide doping,the breakdown field strength of the composite material is seriously deteriorated.In order to further improve the breakdown strength,hexagonal boron nitride(h-BN)with excellent thermal conductivity and electrical insulation properties was selected to be doped into the EPDM polymer matrix and its puncture performance was investigated.Then,in order to obtain a composite medium with more excellent nonlinear conductance characteristics,a zinc oxide whisker with semiconductor properties was prepared by hydrothermal method to modify the EPDM rubber.Finally,according to engineering needs,the breakdown and conductivity characteristics of composite materials at different temperatures were studied.The experimental results show that the nonlinear conductance characteristics of the composites are more excellent with the increase of the amount of zinc oxide doping.When the doping amount of ZnO particles is 30 phr(30 g of doped ZnO when the substrate is 100 g),the composite material begins to exhibit a relatively significant nonlinear conductance.The breakdown performance of the composite is optimal when the h-BN doping amount is 10 phr.The h-BN doping content studied in this paper has a significant effect on the breakdown and conductance characteristics of ZnO/EPDM composites with ZnO particles and ZnO whiskers at 30 phr.After the experiment,a composite material with excellent conductance characteristics and breakdown properties was obtained.The ZnO/EPDM composite prepared from ZnO whiskers at the same doping amount of ZnO exhibits superior nonlinear conductance characteristics.The results show that the breakdown and conductivity characteristics of the composites at different temperatures have significant changes.Although the breakdown field strength has a decreasing trend with increasing temperature,and the composite exhibits more excellent nonlinear conductance characteristics with increasing temperature.