New method for evaluation of water treeing properties of semiconductive materials

An effort was made to develop a simple test method for evaluation of water treeing properties of semiconducting materials. The necessity of an interface between the semiconducting and the insulating parts of the test object, which well reproduce the interfaces in a triple extruded power cable, motivated the use of an object made partly from a coextruded tape. It is shown that the treeing performance of semiconducting materials can be evaluated using such modified Rogowski objects. With the aging parameters adopted in this investigation, an aging time of approximately 10 weeks was necessary. No unambiguous relation between the number of vented trees and the degree of contamination could be found. Nevertheless, the cleanest semiconductor initiated the lowest amount of vented trees, whereas the semiconductor with the most vented trees also contained the highest amount of ionic contamination. The same correlation was found for the length of the vented trees