Numerical and experimental investigation of dielectric recovery in supercritical N₂

Abstract

A supercritical (SC) nitrogen (N 2 ) switch is designed and tested. The dielectric strength and recovery rate of the SC switch are investigated by experiments. In order to theoretically study the discharge and recovery process of the SC N 2 switch under high repetition rate operation, a numerical model is developed. For SC N 2 with initial parameters of p = 80.9 bar and T = 300 K, the simulation results show that within several nanoseconds after the streamer bridges the switch gap, the spark is fully developed and this time depends on the applied electric field between electrodes. During the whole discharge process, the maximum temperature in the channel is about 20 000 K. About 10 µs after the spark excitation of 200 ns duration, the temperature on the axis decays to T axis 1500 K, mainly contributed by the gas expansion and heat transfer mechanisms. After 100 µs, the dielectric strength of the gap recovers to above half of the cold breakdown voltage due to the temperature decay in the channel. Both experimental and numerical investigations indicate that supercritical fluid is a good insulating medium that has a proved high breakdown voltage and fast recovery speed.

Arc Voltage Characteristics in Ultrahigh-Pressure Nitrogen Including Supercritical Region

“…Properties like the density, viscosity, diffusivity, thermal conductivity, and heat capacity of SC nitrogen lie in between the properties of the gaseous and the liquid phases of nitrogen [2]. For successful arc interruption, these properties are crucial, and hence, it is believed that SC nitrogen has the potential to be used as an interruption medium [3].…”

“…Most of the previous works explore small-scale discharges of one millimeter or smaller inter-electrode gaps inside SC carbon dioxide [4]- [9] or SC nitrogen [2], [3], [10] under low energy dissipation, typically in the range of millijoules, while energy dissipations in switching arcs are normally up to hundreds of kilojoules. Exploring the arc properties in ultra-high pressure nitrogen including the SC region is a novel field of research.…”

Anomalous plasma temperature at supercritical phase of pressurized CO<inf>2</inf> after pulsed breakdown followed by large short-circuit current

“…Provided that if the condition of R 2 < 4L/C holds true under R-L-C series circuit, the formulas (2) and (3) can be used. The calculated L and R by formulas (2) and 3…”

Breakdown strength and dielectric recovery in a high pressure supercritical nitrogen switch

“…The model and its details are published in [22]. In the model we simulated the streamer-to-spark transition and the discharge & post-discharge phase inside the SC N 2 breakdown.…”