ac Breakdown Properties and Solidification States of Solidified Alcohol Aqueous Solutions

SUMMARY Electrical insulation system using ice at cryogenic temperature has been studied. Ice has excellent electrical breakdown strength at cryogenic temperature. However, electrical weak points such as voids or cracks are easily formed in ice. Therefore, we tried to suppress the formation of voids...

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Bibliographic Details
Published in:Electrical engineering in Japan 2017-03, Vol.198 (4), p.3-14
Main Authors: TSUCHIYA, RYOHEI, MURAMOTO, YUJI, SHIMIZU, NORIYUKI
Format: Article
Language:English
Subjects:
ac breakdown voltage
Air conditioning
Alcohol
Alcohols
Aqueous solutions
Breakdown
Cooling rate
Cracks
Cryogenic temperature
Cryogenics
Electric potential
Electrical insulation
Ethylene glycol
ice
Ice formation
Propylene
Solidification
solidified aqueous solution
Voids
Voltage
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Summary:SUMMARY Electrical insulation system using ice at cryogenic temperature has been studied. Ice has excellent electrical breakdown strength at cryogenic temperature. However, electrical weak points such as voids or cracks are easily formed in ice. Therefore, we tried to suppress the formation of voids or cracks by mixture of alcohol. In this paper, ac breakdown voltages of ethylene glycol, 1,3‐propanediol, propylene glycol, or glycerin of solidified aqueous solutions were observed. The following results were obtained. (1) In many cases, the ac breakdown voltages of these solidified alcohol aqueous solutions were higher than that of ice. Average breakdown voltage of ethylene glycol shows the highest value among the tested solutions. It is 1.8 times higher than average value of ice. (2) In order to obtain high breakdown properties, it is necessary to adjust alcohol molar fraction so that solidification goes through sherbet‐like matter. (3) ac breakdown voltages of solidified aqueous solutions have very large dispersion. The breakdown voltage of solidified aqueous solution is clarified to be depending on the solidification state. (4) The solidification state of aqueous solution varies with alcohol concentration, cooling rate, and cooling time.
ISSN:0424-7760
1520-6416
DOI:10.1002/eej.22935