Decay of electrical conductance and temperature of arc plasmas

Abstract

Calculations assuming thermal equilibrium have been made of properties of cylindrical arc plasmas which decay after the removal of the electric field. Account is taken of energy losses due to thermal conduction and radiation, self-absorption effects being included where possible in the treatment of radiation. The maximum possible influence of radial convection is calculated by assuming that convective flow maintains a uniform pressure in space and time. Comparisons are made of the calculated decay of electrical conductance with experimental measurements, where available, for A, N 2 , SF 6 , H 2 , and air; curves are given showing the contributions of thermal conduction, convection, and radiatllOn to the decay. The theoretical results underestimate the rapid decays of electrical conductance that have been observed for plasma temperatures of less than 10000 OK in air, and less than 7000 OK in SF 6 , but good agreement between theory and experiment is obtained for argon. Information from rate coefficients supports the view that the rate of atomic recombination to form molecules is insufficient to maintain thermal equilibrium and as a result there is an enhanced rate of cooling. Theoretical transient temperature profiles in air are also compared with published experimental profiles.(1)

Thermal Transfers of SF6Electrical Arcs in High Voltage Circuit Breakers

“…This evolution in two phases has also been noted by Rachard et al in a previous work [6]. Lee et al [7] nd also again in their investigations on SF 6 circuit breakers a succession of a thermal expansion followed by an extinction phase. As one can observe it, the temperature decrease is in good agreement with the literature.…”

“…This paper intends to introduce a new theoretical approach in the aim to follow the temperature evolvement and the thermal transfers during the extinction of the arc plasma by coupling the arc equations with the heat ones. The survey of these transfers has been led rst, for constant values of the deionization time, and afterwards, for variable practical deionization times [5,7]. The data obtained by numerical solving are compared to available experimental results [8,9].…”

The lightning swept stroke along an aircraft in flight. Part I: thermodynamic and electric properties of lightning arc channels

“…Numerical values of the thermal and electrical conductivities are taken from Lowke et al (1973). The radiative losses are the sum of the retardation radiation and the recombination radiation, and can be expressed as (Braginskii 1958) S r = S ret +S rec = 3.48×10 −40 n 2 e T 0.5 +1.35×10 −34 n 2 e T −0.5 (8) where n e is the electron number density.…”

On-line Data Acquisition System for Stationary and Nonstationary Spectroscopic Research

“…Since the determination of the electron density from the Stark-profiles is nearly independent of LTE, there must be a mechanism that causes the deviation from LTE during the decay time. Large gradients and insufficient molecular recombination rates might be the reasons, as Lowke assumes [7]. Comprehensive stationary measurements are at present being conducted in order to study the influence of oxygen upon the LTE and the electron density.…”