TY - GEN
T1 - Bubble dynamics and channel formation for cathode initiated discharges in transformer oil
AU - Cevallos, M.
AU - Butcher, M.
AU - Dickens, J.
AU - Neuber, A.
AU - Krompholz, H.
PY - 2007
Y1 - 2007
N2 - The development of cathode initiated low density channel formation and propagation leading to self breakdown in transformer oil is investigated using high speed electrical and optical diagnostics in a coaxial system with a point/plane axial discharge at various hydrostatic pressures. A cathode initiated channel formation and propagation model based upon single bubble dynamics has been presented by Kattan [1]. Experiments based on high-speed shadowgraphy were conducted to decide if the principles that govern single bubble dynamics could be applied to cathode initiated channel formation. These experiments show bubble motion away from the cathode, with separation velocities on the order of 10's m/s. This separation is similar for single bubbles generated at the cathode and for bubble chains developing into low-density channels. Lifetimes of these channels are recorded and show good correlation with the Rayleigh model [2] used to predict lifetimes of single bubbles. Experiments at reduced hydrostatic pressure reveal a critical pressure below which low density channel expansion occurs, further corroborating the presence of a gas phase. Finally, the pressure dependence of the breakdown voltage due to the expansion of the low density channels is examined and a model for this dependence is presented. The experiments conducted confirm the presence of a gas phase channel, its correlation with single bubble dynamics, and its importance to final breakdown.
AB - The development of cathode initiated low density channel formation and propagation leading to self breakdown in transformer oil is investigated using high speed electrical and optical diagnostics in a coaxial system with a point/plane axial discharge at various hydrostatic pressures. A cathode initiated channel formation and propagation model based upon single bubble dynamics has been presented by Kattan [1]. Experiments based on high-speed shadowgraphy were conducted to decide if the principles that govern single bubble dynamics could be applied to cathode initiated channel formation. These experiments show bubble motion away from the cathode, with separation velocities on the order of 10's m/s. This separation is similar for single bubbles generated at the cathode and for bubble chains developing into low-density channels. Lifetimes of these channels are recorded and show good correlation with the Rayleigh model [2] used to predict lifetimes of single bubbles. Experiments at reduced hydrostatic pressure reveal a critical pressure below which low density channel expansion occurs, further corroborating the presence of a gas phase. Finally, the pressure dependence of the breakdown voltage due to the expansion of the low density channels is examined and a model for this dependence is presented. The experiments conducted confirm the presence of a gas phase channel, its correlation with single bubble dynamics, and its importance to final breakdown.
UR - http://www.scopus.com/inward/record.url?scp=45149096877&partnerID=8YFLogxK
U2 - 10.1109/PPC.2005.300578
DO - 10.1109/PPC.2005.300578
M3 - Conference contribution
AN - SCOPUS:45149096877
SN - 078039190X
SN - 9780780391901
T3 - Digest of Technical Papers-IEEE International Pulsed Power Conference
SP - 1235
EP - 1238
BT - 2005 IEEE Pulsed Power Conference, PPC
T2 - 2005 IEEE Pulsed Power Conference, PPC
Y2 - 13 June 2005 through 17 June 2005
ER -