Effect of Degassing Time on Initiation of Electrical Tree in XLPE

Abstract

Polar crosslinking by-products are prone to be produced in the process of preparing crosslinked polyethylene (XLPE) by peroxide crosslinking method. These cross-linking byproducts remain in the dielectric, which is easy to cause electric field distortion. The electrical tree will be caused at the electric field distortion, it tends to degrade or even breakdown the cable insulation. Therefore, it is necessary to explore the changes of the varieties and contents of crosslinking by-products in the degassing process of XLPE, so as to study the effect of degassing process on the initiation of electrical tree in XLPE. XLPE sheet samples were prepared by hot pressing method. Samples degassed for 0d, 2d, 4d and 6d were obtained in a vacuum drying oven at 70°C. Initiation of electrical tree experiments were carried out on four groups of samples. The varieties and contents of crosslinking by-products were characterized by gas chromatography-mass spectrometry (GC-MS), and the effects of crosslinking by-products on the initiation of electrical tree with different degassing time were studied. The results show that under the set degassing conditions, the sample degassed for 2 days has the highest electrical tree initiation voltage. Compared with degassed 0d, the sample degassed 2d has less pores and relatively dense structure. Compared with degassing for 4d and 6d, the content of acetophenone in degassing for 2 days is higher, and acetophenone as a voltage stabilizer has a good inhibitory effect on electrical tree.