Title :
Breakdown behavior of cryogenic liquids in the presence of thermal bubbles under ramped voltage
Author :
Hara, Masanori ; Koishihara, Hironori ; Saita, Kenji
Author_Institution :
Dept. of Electr. Eng., Kyushu Univ., Fukuoka, Japan
fDate :
8/1/1991 12:00:00 AM
Abstract :
V-t characteristics were measured and the thermal bubble deformation was observed in liquid nitrogen and helium with a ramped voltage, simulating the quenching conditions in large superconducting magnet coils. From the experimental results, the breakdown process of liquid coolants in the presence of thermal bubbles was classified into three categories depending on the voltage slope: (1) breakdown through a composite insulation system of undeformed bubbles and surrounding cryogenic liquid with fast rising voltage such as the standard lightning impulse voltage; (2) breakdown through a strongly elongated bubble by an electric field with the rise time of milliseconds; and (3) breakdown through a vapor bridge of the gap, formed by growth of a bubble fixed on an electrode with a hot spot, by electric fields rising in ~100 ms
Keywords :
bubbles; electric breakdown of liquids; insulating materials; liquid helium; nitrogen; He; N2; V-t characteristics; breakdown; composite insulation system; cryogenic liquids; hot spot; lightning impulse voltage; liquid coolants; quenching; ramped voltage; strongly elongated bubble; superconducting magnet coils; thermal bubbles; vapor bridge; Breakdown voltage; Cryogenics; Deformable models; Dielectric liquids; Electric breakdown; Helium; Nitrogen; Superconducting coils; Superconducting magnets; Thermal quenching;
Journal_Title :
Electrical Insulation, IEEE Transactions on
