The UNIPEDE/DISCAB approach to a water treeing test for medium voltage polymeric cables. Background and test experience

In Europe, UNIPEDE/DISCAB started to collect polymeric cable fault statistics in 1984 which showed that the faults are most often related to vented water trees from insulation screens made of semiconducting paint and tapes. When the UNIPEDE/DISCAB-group appointed an ad-hoc group to propose a water treeing test for European standardisation they looked to the research companies that had been working in this field for many years. The proposed test is based on findings from labs over the last ten to twenty years. The test was built around moderate ageing conditions. The reason was to avoid initiation of irrelevant ageing phenomena not occurring in service. The author briefly outlines the following aspects of the test: conditioning, ageing voltage, frequency, temperature, ageing time, and approval tests