Study on the Electrical Properties of Low‐Density and High‐Density Polyethylene Blends for High‐Voltage Direct Current Cable

Blending low‐density polyethylene (LDPE) with high‐density polyethylene (HDPE) is an effective strategy to improve electrical properties for the high voltage direct current (HVDC) power cable insulation. However, the effects of HDPE on the space charge accumulation of the HDPE/LDPE blends are rarely reported. In this paper, the HDPE/LDPE blends are prepared with different HDPE contents, and their space charge distribution, conductivity, breakdown strength, surface potential decay, and morphology are measured, respectively. The results show that the optimal content range for the space charge inhibition is from 3 to 10 wt%. For the 10 wt% blend, it is 29.5% smaller in average space charge density than pure LDPE. Moreover, the 10 wt% blend is 85.5% lower in conductivity and is 33.7% higher in breakdown strength compared with pure LDPE. Thick lamellae structure is introduced into HDPE/LDPE by HDPE, and it leads to the formation of deep traps, contributing to the improvement of the electrical properties of the blends. This study provides a valuable foundation for the design of the new HVDC power cable insulating material.