Dissipation Current Waveforms Monitoring under Water Tree Deterioration Test of LDPE Sheet

The dissipation current waveform observation method is considered one of possible way as a diagnostic method for the un-bridged water tree on the high-voltage class power cable. In this paper, in order to clarify the time variations with the un-bridged water tree growth, by using the special chamber and setup, the dissipation current waveforms monitoring under the high voltage application test of LDPE sheet with soaking the sample into the saline solution was carried out at the applied frequency 1 kHz and applied voltage 2 kVrms for 300 hours. As the results of the high voltage application test, it was confirmed that the electric field dependence of the phase of 3rd harmonic of dissipation current strongly related with the deterioration rate of un-bridged water tree.