Diagnosis and restoration of water tree aged XLPE cable materials

One main purpose of this work was to study the effects of silicone restoration liquid on water treed XLPE power cable insulation materials. Evaluation parameters used were AC and impulse breakdown strengths as well as water tree examinations. In addition, a nondestructive diagnostic method was used to evaluate the degree of water treeing and restoration. The laboratory experiments were performed on water tree aged Rogowski-type test objects with semiconducting screens and an insulation thickness of 0.7 mm. The results show that the short-term effect of restoration is to strongly increase the AC and impulse breakdown strength. The long-term performance, however, has to be further examined. Return voltage measurements may become a useful diagnostic tool for evaluating the degree of water treeing and restoration of XLPE power cable insulation