Synergistic improved electrical resistivity-temperature characteristics and DC breakdown strength in insulating XLPE composites by incorporating positive temperature coefficient particles

Weakening the electrical resistivity-temperature dependence of cross-linked polyethene (XLPE) is an effective way to enhance the electric field uniformity of high-voltage direct current (HVDC) cables. Therefore, an attempt is made to suppress the negative temperature coefficient (NTC) of electrical resistivity by incorporating BaTiO3- based ceramic fillers with positive temperature coefficient (PTC) electrical resistivity into XLPE. Morphology characterization indicated that PTC particles were well dispersed in the XLPE matrix. The measurements of electrical resistivity and DC breakdown strength are carried out from 30 degrees C to 90 degrees C. The electrical resistivity and DC breakdown strength of the sample at high temperatures were significantly improved with the introduction of PTC particles, which is attributed to the deep traps near the Curie temperature region. The high doping content has a better suppression of the NTC effect. The activation energy (0.63 eV) and NTC strength (1.74) of the sample with the addition of 10 wt% of PTC are considerably reduced compared with XLPE. The content of PTC particles was positively correlated to the enhancement of electrical resistivity and DC breakdown strength. The optimum content for DC breakdown strength is about 5 wt%. The low electrical resistivity-temperature dependence of insulation performance shows a potential to obtain temperature-stable HVDC cable insulation.

Automated summary

This study aimed to enhance the electric field uniformity of high-voltage direct current (HVDC) cables by reducing the electrical resistivity-temperature dependence of cross-linked polyethene (XLPE). This was achieved by incorporating BaTiO3-based ceramic fillers with positive temperature coefficient (PTC) electrical resistivity into XLPE. The results showed that the addition of PTC particles significantly improved the electrical resistivity and DC breakdown strength of the sample at high temperatures, which was attributed to the presence of deep traps near the Curie temperature region. The higher the doping content of PTC particles, the better the suppression of the negative temperature coefficient (NTC) effect. The optimum content for DC breakdown strength was found to be about 5 wt%.