Long Time Range Breakdown Caused by Penetration of Positive Charges Packet in Low Density Polyethylene Sheets

• DOI: 10.15676/ijeei.2013.5.2.1
• Publication Date: 2015-02-13T12:09:57Z
• Authors: Amir Izzani Mohamed; Takashi Akagi; ; Ryotaro Ozaki; ; Kazunori Kadowaki
• Keywords: 02 engineering and technology; 0210 nano-technology

This paper presents an experimental study on long time range breakdown of Low Density Polyethylene (LDPE) under very high dc applied fields (Emean) of 2.0 MV/cm or 3.0 MV/cm. Breakdown time lag and space charge distribution are simultaneously measured for a 200-µm-thick LDPE sheet with positive-semicon and negative-evaporated Al electrodes. A voltage is applied to the sheet until the dc breakdown occurs. 20 samples are tested for both the applied voltages. It should be remarked that 50 % survivor probability T50 , corresponding to time in which breakdown occurs for 10 samples out of 20, is 70 min for 40 kV, whereas it is 90 min for 60 kV. Results of the space charge measurement by pulsed electro acoustic (PEA) method indicates that a large number of positive charges are injected from the semicon-anode and they are accumulated in the bulk of LDPE, so that field distribution in LDPE is strongly distorted. The maximum field strength Emax(t) in LDPE after the space charge penetration for 60 kV becomes higher than that for 40 kV. However, the distortion ratio Emax(t) / Emean under 40 kV is higher than that under 60 kV. This is because the positive charges packet produced by 40 kV penetrates into deeper area of the bulk as compared with that by 60 kV.