An experimental study about the treeing phenomena in XLPE subjected to distorted voltages

In this work the influence of harmonic content of the voltage waveform on electrical treeing growth in XLPE (cross-linked polyethylene) is investigated. In particular the lifetimes of XLPE specimens, having a point plane electrode configuration, subjected to different distorted voltages containing 3/sup rd/, 5/sup th/ and 7/sup th/ harmonics, are measured. A lifetime prediction model based upon the correlation between recorded durations and the maximum amplitude of the applied voltages is proposed. The model resulted well suited for the investigated cases. Digital images acquisition allowed to monitor treeing growth so to check wether bush or branch type of treeing had been growing during the tests.