Thermal Interruption Performance of Ultrahigh-Pressure Free-Burning Nitrogen Arc

Abstract

In this paper, an experimental investigation of the thermal interruption performance of free-burning nitrogen arcs at 1 bar, 20 bar, and 40 bar filling pressures is reported. This work contributes to the fundamental understanding of arc characteristics at very high gas filling pressures. A resonant circuit is used to generate an arc peak current of 130 A at a frequency of 190 Hz. An ignition copper wire initiates the arc between a 4 mm diameter pin electrode and a ring electrode. The arc burns freely at a fixed inter-electrode gap of 50 mm without any forced gas flow. A resistive-capacitive branch parallel to the arc controls the initial rate of rise of recovery voltage. By changing the parallel resistance, the rate of rise of recovery voltage is varied from 9.8 V/µs to 84.8 V/µs. Time to reignition and the corresponding re-ignition voltages are considered as the primary parameters to characterize the thermal interruption performance. It is observed that the re-ignition time rises with the decrease of rate of rise of recovery voltage at all pressure levels, which is expected. However, in the absence of a forced gas flow, high gas filling pressure results in a reduction of the time to re-ignition and the re-ignition voltage in contrast to atmospheric pressure nitrogen arc.

Effect of filling pressure on post-arc gap recovery of N2

“…A relatively high post-arc current may facilitate the glow to arc transition at high N2 pressure, which would reduce the cathode-fall voltage [25]. In a recent study on the thermal interruption performance in the free-burning arc, the re-ignition voltage was observed to be lower at high filling pressures compared to at 1 bar [14]. In this paper, within the first 300 µs after CZ, the breakdown voltage is observed to be almost fixed.…”

“…Without forced gas flow, the thermal energy stored in the arc core fails to dissipate quickly. As a result, a relatively high post-arc current is observed for the arc burning at a high N2 filling pressure [14]. A relatively high post-arc current may facilitate the glow to arc transition at high N2 pressure, which would reduce the cathode-fall voltage [25].…”

“…First, a freeburning arc and the influence of tube constriction on the arc have been investigated in the SC state and beyond, up to 80 bar filling pressure during the high current phase [12], [13]. Some further investigations were focused on the region near CZ, where the effect of N2 filling pressure on the thermal interruption performance is evaluated [14]- [16]. The arc voltage is reported to increase with the filling pressure, whereas no abrupt change in arc voltage is observed during the transition of N2 from gas to SC region [12].…”

Arc extinction with nitrogen at 1-40 bar in a puffer-like contact configuration

“…The results showed that increasing the nitrogen filling pressure from 1 to 40 bar abs caused an almost threefold increase of the arc voltage. The arc-voltage characteristics for wall-restricted arcs, both thermal interruption capability and dielectric recovery rates in the contact gap after short (0.5-2.6 ms) current half-cycles, have also been published [4][5][6][7][8][9]. Moreover, dielectric recovery and arc characteristics in high-pressure (supercritical) CO 2 have been studied [10].…”

“…This paper reports on current-interruption experiments with a puffer-like contact configuration and nitrogen as the current interruption medium. In contrast to previous work [3][4][5][6][7][8], an upgraded test circuit with a current waveform close to 50 Hz is used. The current interruption capabilities at nitrogen filling pressures of 1, 10, 20 (subcritical) and 40 bar abs (supercritical state) were compared, using the same contact configuration and puffer design.…”