Effect Of LDPE-based Composite Electrode On Space Charge Injection Of Polyethylene

Semi-conductive shielding layer is an important part of HVDC cables structure,which can evenly distribute the electric field in the insulation layer,preventing the electric field distortion,reducing the electric stress concentration,and improving the breakdown strength of the insulation layer.The quality of semi-conductive shielding layer play an important role on the service life and the safety of HVDC cables,but it is also the important bottleneck of the rapid development of HVDC cables.In this paper,the appropriate amounts of modified components were added to the masterbatch which prepared of the conductive carbon black(CB)and the low-density polyethylene(LDPE)by the internal mixer to prepare the semi-conductive composites with high performance as the HVDC cable semi-conductive shielding material.The properties of the semi-conductive electrode materials were analyzed by resistivity testing,tensile testing,scanning electron microscopy,space charge measurement etc.1.Polyacene quinone(PAQR)polymer was prepared by melting salt method,then added into CB/LDPE masterbatch by using to prepare semi-conductive composite materials.The effect of the space charge injection on the insulation layer was explored by PEA and TSC.The results show that with the increase of PAQR content,the inhibtion of the PAQR/CB/LDPE semi-conductive electrode inject space charge on the insulation layer is gradually enhance.2.The semi-conductive composites of CB/LDPE/EVA have been prepared by the methods of melting blend and hot-press crosslinking.These performance of tensile strength,resistivity,crosslinking degree,thermal aging,thermal elongation and rheological was tested.The results show that with the increase of EVA content,the elongation at break of CB/LDPE/EVA system increases,but the tensile strength decreases;The thermal extension test results of CB/LDPE/EVA system meet national standards;The capillary rheological tests show that CB/LDPE/EVA system has low shear viscosity,and that the surface of the capillary extruded sample was super smooth.By comparison,it is found that the comprehensive performance of our sample is close to that of the imported HVDC semi-conductive shielding material.3.In this paper,the influence of the change of CB content on the resistivity of semi-conductive electrode and the injection of the space charge on the insulation layer also were studied in the system of CB/LDPE/EVA.The results show that with the increases of CB content,the resistivity of the semi-conductive electrode decreases.Until the content of CB exceeds 25 %,the decrease of resistivity is not obvious,showing that the sample is close to the percolation value of conductive resistance under this CB content.The PEA test show that with the increase of the content of CB in semi-conductive electrode,the space charge density of the insulating layer increase firstly and then decrease.