Morphological study of treeing phenomena in PE and XLPE

The authors have been studying to improve the performance of insulation materials in order to promote a significant increase in the reliability and the cost advantages of XLPE cables. Towards that end, a method to observe the supermolecular structures of insulation materials and the treeing phenomena directly and simultaneously has been developed, and is herein discussed. The method was applied to the observation of actual XLPE cable insulation successfully. Generation of micro cavities were found at the amorphous region between the lamellae in the electrical-charged specimens, so it is believed that studies on the lamellae and the amorphous region are important to promote the understanding of the treeing mechanism.