Modulated electrical performance of cross-linked polyethylene by grafted charge-attracting molecules for high voltage direct current cable insulation

In order to figure out the effects of charge-attracting molecules on the direct current electrical performance of crosslinked polyethylene (XLPE), the molecules with different structures and functional groups were grafted onto XLPE, and their space charge, volume resistivity and thermal stimulated depolarization current were investigated. Based on density function theory, the trap distribution and charge-attracting properties of the grafted XLPE were calculated. For the charge-attracting groups, the results indicate that with the grafted of trap molecules containing polar groups CO and N-H, the electron and hole traps are introduced and the ability of attracting negative charges and positive charges are extremely improved, respectively, resulting in the enhanced space charge hindering and suppressed resistivity. The benzene ring can form both electron and hole traps with relatively shallower energy level, and results in an improved space charge dissipation and decreased resistivity. For the combination of charge-attracting groups, the continuous arrangement of homogeneous charge-attracting groups can achieve an enhanced modification effect, and heterogeneous charge-attracting groups will attenuate the modification ability. For the molecule structure, the grafting of compact cyclic molecular can affect the electrostatic potential distribution on XLPE's chain, and exhibits a stronger modification effect.