Research on Correlation Between Thermal Aging and Electrical Treeing of Cross-Linked Polyethylene Cable

Thermal aging may influence not only physiochemical performance of cross-linked polyethylene cable's insulation but also the initiation and propagation of electrical tree.The behavior of electrical tree after long time thermal aging of cable insulation is studied,and the relationship between thermal aging and electrical treeing in XLPE cable insulation is discussed.Thermal aging test were carried out at three levels of temperature 120 ℃,140 ℃ and 160 ℃.Needle-board structure electrode was used to cause electrical trees and electron microscope was used to watch initiation and growth of trees.The physicochemical characteristics of XLPE cable insulation after thermal aging at different temperature were tested by DSC and FTIR.The results show that the increasing of polar groups and the degradation of macromolecules,resulting from the thermal oxidation of XLPE cable insulation in thermal aging test,lead to more unhomogeneous structure of the material.Finally,the growth principles of several different type trees are discussed.The conclusion is drawn that thermal aging does not accelerate the growth of electrical treeing,but retard it.