Effect of Li1.3Al0.3Ti1.7(PO4)3 on semiconductive composites: Positive temperature coefficient (PTC) performance and inhibition of space charge injection

The semiconductive layer located between the core and insulation layer of a high-voltage DC (HVDC) cable can inhibit the accumulation of space charge in the insulation layer. This helps increasing the electric field inside the cable, thus improving the stress distribution of the electric field on the inner and outer surfaces of the insulation layer and the electrical strength of the cable. An inevitable positive temperature coefficient effect (PTC) in the semiconductor layer leads to aging failure of the insulation layer. To improve this phenomenon, the semiconductive shielding layer was modified for suppressing its PTC effect and reducing the space charge injection into the insulation layer. Li1.3Al0.3Ti1.7(PO4)3(LATP) was prepared via a solid-phase reaction and added to a composite consisting of carbon black (CB), ethylene vinyl acetate copolymer (EVA), and low-density polyethylene (LDPE). Resistivity, thermally stimulated depolarization current (TSDC), and pulsed electroacoustic (PEA) measurements were performed on the modified sample. The results showed that when the LATP content was 4 wt%, the modification effect of the semiconductive shielding layer was most effective, the PTC effect was reduced by 11%, and the space charge injection into the insulating layer was improved significantly.