Breakdown of LDPE Film under Heavy Water Absorption

The breakdown strength characteristic of Low Density Polyethylene films (LDPE) under DC voltage application and the effect of water absorption have been studied. Mainly, our experiment was investigated under two conditions; dry and heavy water absorption. Under DC ramp voltage, the result found that the breakdown strength under heavy water absorption has a lower value than dry condition. In order to clarify the effect, the temperature rise of film was observed using non contact thermograph until the occurrence of the electrical breakdown and the conduction current of the sample was also measured in correlation with the thermograph measurement. From the observations, it was shown that under the heavy water absorption, the hot spot in the samples appeared at lower voltage. At the same voltage the temperature of the hot spot and conduction current was higher than that under the dry condition. The measurement result has a good correlation between the existence of a critical field for conduction current and thermograph observation. In case of the heavy water absorption, the occurrence of the threshold field was earlier than the dry condition as result lead to higher of conduction current and the temperature rise appears after threshold field was significantly increased in increasing of field. The higher temperature rise was caused by the higher current conduction as the result the insulation leads to breakdown to the lower field application.

Authors:

• Eka PW
• T. Okazaki
• Y. Murakami
• N.
• Hozumi
• M. Nagao

Keywords:

• Low density polyethylene
• heavy water absorption
• conduction current
• temperature rise.

References:

[1] Tanaka T: "Charge Transfer and Tree Initiation in Polyethylene Subjected
to ac Voltage Stress", IEEE Trans. on Elect. Insul. 27, pp. 424-432, 1992.
[2] P.HF Morshius: "Degradation of Solid Dielectrics due to Internal Partial
Discharge: Some thoughts on progress made and where to go now",
IEEE Trans. on Dielect. And Elect. Insul. 12, pp. 905-913, 2005.
[3] M. Nagao, Takashi Kimura, Yukio Mizuno, Masamitsu Kosaki and
Masayuki Ieda: "Detection of Joule Heating before Dielectric Breakdown
in Polyethylene Films", IEEE Trans. on Elect. Insul.25, pp.715-722. 1990
[4] Y Murakami, N Hozumi,and M Nagao: "Surface Temperature
Measurement and Analysis of Thermal Breakdown with Ethylene-vinyl
Acetate Copolymer in Room-Temperature Region",JJAP.Vol. 43, No. 9A,
pp.6184-6187, 2004.
[5] K Kaneko, T Ozaki, E Nakae and T Mizutani, " Effect of space charge and
conduction phenomena in Polyimide Films" 2005 Annual Report
Conference on Electrical Insulation and Dielectric Phenomena, pp
657-660, 2005
[6] L.A Dissado, C Laurent, G.C. Montanary, and P. H. F. Morshuis,
" Demonstrating a Threshod for Trapped Space Charge Accumulation in
Solid Dielectrics under dc Field", IEEE Trans. on Dielect. And Elect.
Insul.Vol. 12, No. 3, pp 612-620, 1990.