Conductivity of HVDC Cable Insulation Materials: Case Study between XLPE Nanocomposite and Polymer Filled XLPE

摘要

Extruded HVDC power cables have been aroused intensive attention in the recent years and a rapid rise in voltage level for cable systems highlights the electrical tolerance of insulation materials. As one of the key factors for HVDC cable insulation design, conductivity is required to be low enough to reduce thermal runaway. Various methods have been used to decrease conductivity of crosslinked polyethylene (XLPE). However, a significant obstacle for conductivity measurement is to obtain a representative results from a short time test. In this study, based on the same low density polyethylene (LDPE), conductivity of a nano Al₂O₃/XLPE composite and a polymer filled XLPE from 30°C to 90°C were investigated. It reveals that recorded current curves of nano composite show a similar behavior to ordinary XLPE, which differs significantly from that of the polymer filled XLPE. The reason may lie in space charge behaviors in these samples. And calculated conductivity of polymer filled XLPE is much lower than that of nano Al₂O₃/XLPE composite below 70°C and ordinary XLPE. Addition of polymer fillers increases thermal activation energy more significantly than nano-fillers does. These results may give an inspiration for the measurement of conductivity and development for HVDC cable insulation materials.