Effect of Electrode Material on Space Charge in LDPE under continuous polarity inversion DC Field

As an insulating material widely used in the field of power cables, low-density polyethylene can produce space charge accumulation under high voltage DC stress, resulting in electric field distortion and insulation failure. Different electrode materials have different effects on LDPE space charge accumulation. Therefore, it is necessary to study the correlation between electrode materials and LDPE charge accumulation. In this paper, two different electrode pairs of upper electrode gold and lower electrode gold and upper electrode gold and lower electrode aluminum were selected, and space charge behavior of LDPE under continuous polarity inversion electric field was measured by electroacoustic pulse method. The results show that for the sample with upper electrode gold and lower electrode gold,the space charge distribution at the interface of electrode and sample is symmetrical, while the space charge distribution is obviously asymmetric for the sample with upper electrode gold and lower electrode aluminum,and the internal space charge distribution is more complex; Compared with the sample with upper electrode gold and lower electrode gold, it is easier for the sample with upper electrode gold and lower electrode aluminum to accumulate space charge and cause higher electric field distortion under high electric field. It is analyzed that different lower electrode materials may lead to different space charge characteristics: aluminum has higher work function and lower interface potential barrier than gold under high field,thus it is easier for aluminum to inject space charge into the sample.