Dissipation current waveform observation of water tree deteriorated LDPE

Water tree degradation phenomenon is the one of typical problem for electrical insulation of power cable. In this paper, in order to examine the water tree´s fundamental properties, the dissipation current waveform observations are carried out by using the both of water tree deteriorated and un-deteriorated low-density polyethylene (LDPE) sheet samples. As the results of experiments, when the length and the number of water tree is short and small in the specimen, the difference of the detected dissipation current waveforms between the water tree deteriorated and un-deteriorated LDPE was small. By using FFT technique, the electric field dependences of fundamental and third harmonics are examined. And then it is found that the trend of the electric field dependence of third harmonics between the water tree deteriorated and un-deteriorated LDPE is slightly different.