Space charge behaviors and electrical insulation characteristics in <scp>EPDM</scp> /micro‐ <scp>SiC</scp> composite with surface‐modified nano‐ <scp>SiC</scp> for <scp>HVDC</scp> insulation

Abstract Nano‐sized semiconductive silicon carbide (nano‐SiC) is incorporated into an ethylene propylene diene monomer (EPDM)/micro‐SiC composite in order to prepare an electrical insulation compound for high voltage direct current (HVDC). The nano‐SiC surface is modified with 1,3‐divinyl‐1,1,3,3‐tetramethyldisilazane, and the effects of surface‐modified nano‐SiC content on the space charge characteristics, tensile strength, and electrical insulation characteristics are studied. An EPDM/micro‐SiC/nano‐SiC composite is prepared by a two‐roll mill. The weight ratios of EPDM rubber, micro‐SiC, and nano‐SiC are 96 g:2.5 g:0.0–3.0 g. When 2.0 g of a semiconductive nano‐SiC particle is incorporated into an EPDM (96 g)/micro‐SiC (2.5 g) composite, the space charge is adequately dispersed throughout the composite, and therefore, the HVDC breakdown strength increases. However, if the nano‐SiC is mixed in excess, a conductive passage is formed, causing the HVDC breakdown strength to decrease. HVDC breakdown strength for the composite with 2.0 g nano‐SiC under positive polarity power supply shows the maximum strength of 104.6 kV/mm. However, excessive mixing of nano‐SiC particles has a negative effect on the HVDC breakdown strength. Tensile strength for the composite with 2.0 g nano‐SiC shows the maximum value, 5.4 MPa. Highlights The surfaces of micro‐ and nano‐SiC particles were modified with 1,3‐divinyl‐1,1,3,3‐tetramethyldisilazane. An EPDM/micro‐SiC/nano‐SiC composite was produced by a two‐roll mill. Semiconductive nano‐SiC particles improved HVDC breakdown strength by dispersing the space charge within the EPDM composite. However, if the nano‐SiC was mixed in excess, a conductive passage was formed, causing the HVDC breakdown strength to decrease.