TY - GEN
T1 - Composite shadowgraphy and luminosity images of self breakdown discharge channels in transformer oil
AU - Cevallos, M.
AU - Butcher, M.
AU - Dickens, J.
AU - Neuber, A.
AU - Krompholz, H.
PY - 2007
Y1 - 2007
N2 - The physics of cathode initiated discharge formation 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. Previous research conducted on self breakdown channel formation using high speed shadowgraphy and photography of the emitted light has shown tree-like structures for both cathode and anode initiated discharges, with characteristic differences. Cathode initiated discharges expand faster to a more "bushy" appearance, whereas anode initiated discharges show branching localized channels. So far, the spatial resolution to detect small luminous areas in pre-breakdown discharges and to determine their correlation to low density regions visible in the shadowgraphs was not sufficient in the experiments described in this paper, thus a systematic variation of exposure times, and time delays between luminosity pictures and shadowgraphy pictures has been performed. These experiments confirm that the luminosity emitted during prebreakdown events is generated from the low density regions seen in the shadowgraphy images, indicating charge amplification mechanisms in the gas phase for cathode initiated events. This statement is further supported by the dependence of both the channel dynamics and the light emission at lowered hydrostatic pressure.
AB - The physics of cathode initiated discharge formation 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. Previous research conducted on self breakdown channel formation using high speed shadowgraphy and photography of the emitted light has shown tree-like structures for both cathode and anode initiated discharges, with characteristic differences. Cathode initiated discharges expand faster to a more "bushy" appearance, whereas anode initiated discharges show branching localized channels. So far, the spatial resolution to detect small luminous areas in pre-breakdown discharges and to determine their correlation to low density regions visible in the shadowgraphs was not sufficient in the experiments described in this paper, thus a systematic variation of exposure times, and time delays between luminosity pictures and shadowgraphy pictures has been performed. These experiments confirm that the luminosity emitted during prebreakdown events is generated from the low density regions seen in the shadowgraphy images, indicating charge amplification mechanisms in the gas phase for cathode initiated events. This statement is further supported by the dependence of both the channel dynamics and the light emission at lowered hydrostatic pressure.
UR - http://www.scopus.com/inward/record.url?scp=45149115434&partnerID=8YFLogxK
U2 - 10.1109/PPC.2005.300459
DO - 10.1109/PPC.2005.300459
M3 - Conference contribution
AN - SCOPUS:45149115434
SN - 078039190X
SN - 9780780391901
T3 - Digest of Technical Papers-IEEE International Pulsed Power Conference
SP - 982
EP - 985
BT - 2005 IEEE Pulsed Power Conference, PPC
Y2 - 13 June 2005 through 17 June 2005
ER -