Spectroscopic measurements of streamer filaments in electric breakdown in a dielectric liquid

Abstract

Abstract. Emission spectroscopy has been utilized to provide information about the electron density and temperature in streamers and breakdown arcs in transformer oil. Recorded spectra include strongly broadened hydrogen Balmer-α lines and vibration/rotation band profiles of the C 2 molecule. The origin of the observed broadening of hydrogen lines is discussed and it is concluded that it arises mainly from collisions with charged particles, so-called dynamic Stark broadening. By assuming that the broadening is due solely to dynamic Stark broadening, electron densities between 1 × 10 18 and 1 × 10 19 cm −3 were obtained for the rear of positive streamer filaments during the later stages of propagation. For negative streamers we obtained an upper limit of 3 × 10 16 cm −3 and for breakdown arcs electron densities up to 4 × 10 18 cm −3 . The temperature information in the C 2 emission profiles and the intensity ratio of the hydrogen Balmer lines are discussed. Rough estimations of the temperature are presented both for positive and for negative streamers.

Spatially and temporally resolved electron density measurements in streamers in dielectric liquids

“…The idea that a dense plasma was situated at the centre of the streamer was put forward in the earlier work. It was then suggested that the streamer, like a gas discharge at high pressure, might experience a constriction of the conducting volume towards the centre of the discharge [14]. This intuitively seems a likely explanation.…”

“…The earlier measurements presented by our group on positive streamers yielded very high electron densities, of the order of 10 18 or even 10 19 cm −3 [14]. These values were obtained late in the propagation process but the experimental technique did not provide measurements of sufficient quality to allow one to study the earlier stages.…”

“…Further spectroscopic work concentrating on analysis of the properties of the streamer plasma has been presented in [14].…”

Influence Estimation of the Voltage Value on the Measurement Results for the Optical Radiation Generated by Partial Discharges on Bushing Isolator

“…Based on literature reports [1][2][3][4][5][6][7][8][9][10][11] it can be concluded that at an adequate regime of metrology, the optical spectrophotometry method not only enables for accurate detection of radiation generated by electrical discharges, but also for widely understood analysis.…”

“…However, measurements results reported in the literature confirm the high sensitivity of this method, revealing by changes of model parameters and tests conditions. Thus it becomes possible to study a number of phenomena inaccessible by application of conventional diagnostics for insulation systems of electric power devices such as the electric, gas chromatography and the acoustic emission methods [1][2][3][4][5][6][7][8][9][10][11].…”