Water treeing and breakdown strength reduction of XLPE insulation

An effort was made to determine factors influencing initiation and growth of vented water trees and to study the reduction of breakdown strength caused by water treeing. Water treeing experiments were performed on both cable samples and Rogowski-type test objects. The influence of aging time and electric field stress was elucidated. In order to test the hypothesis that water treeing basically is a mechanical damage phenomenon connected with environmental stress cracking (ESC), the authors performed water tree experiments with stress-cracking active agents added to the water. It is shown that initiation of vented water trees is considerably enhanced by the presence of the agents