3D CFD Arc Fault Simulation in Gas-Insulated Switchgears

Arc fault processes can lead to strong damages in gas-insulated switchgears and have to be considered in the development process. In order to reduce test costs, the development of overpressure protection systems can be supported by CFD arc fault simulations. The paper deals with the modelling and simulation of arc fault processes in gas--insulated switchgears. The developed simulation tool takes into account a three-dimensional arc model and the opening of a rupture disc during the arc fault process. The influence of different insulating media as e.g. SF6, Air and CO2 on the arc fault process has been investigated. The simulation model has been validated by measured signals for pressure build-up and arc voltage

CFD Arc Simulation of a Switching-off Process in a Model Chamber

This paper deals with the investigation of the switching arc process in a model chamber by CFD arc simulation. A transient axisymmetric model based on the @Fluent software is used. The applied arc model considers electromagnetic phenomena, radiative transfer, ablation of PTFE parts and pin motion as well. The influence of the boundary conditions for the solution of the current continuity equation is highlighted. The obtained results are validated by measurements on the model chamber [1]

Modelling and Simulation of SF6 High-Voltage Circuit-Breakers - an Overview on Basics and Application of CFD Arc Simulation Tools

The paper gives an overview on the basics of CFD arc simulation tools with respect to the simulation of the fluid mechanical processes in the interrupter unit of SF6 high-voltage circuit-breakers at no-load and short-circuit switching-off processes. On the example of SF6 self-blast circuit-breakers the complete process from the analysis of the switching-off process to the creation of a modular simulation model consisting of several sub models is illustrated. Details to the modelling in the particular sub modules and to the implementation are given. The capability of a CFD arc simulation tool based on the program package ANSYS/FLUENT is demonstrated on the basis of selected simulation results. Furthermore case examples for the application of the presented CFD arc simulation tool in the development process of high-voltage circuit-breakers are given

INFLUENCE OF COPPER VAPORS IN SF 6 PLASMA

International audienceIn this study a theoretical approach allows estimating the ablation mass flux of copper from a corrected Hertz-Knudsen flux. The influence of the copper vapours coming from the anode electrode to an SF 6 plasma is studied in a simplified 2D configuration. Depending on the plasma pressure an ablation or a diffusion state is considered. The amount of copper versus time is presented. An RMS current I=10kA is applied leading at t=10ms to an amount of copper equal to 0.6mg. The vapours change the plasma properties mainly the electrical conductivity and radiation and so the plasma behaviour. At time t=5ms the electrode erosion leads to a copper plasma. This simple case shows the necessity to well consider the copper erosion in plasma modelling as in High Voltage Circuit Breaker (HVCB) where higher current are considered

Influence of Copper Vapors in SF6 Plasma

In this study a theoretical approach allows estimating the ablation mass flux of copper from a corrected Hertz-Knudsen flux. The influence of the copper vapours coming from the anode electrode to an SF6 plasma is studied in a simplified 2D configuration. Depending on the plasma pressure an ablation or a diffusion state is considered. The amount of copper versus time is presented. An RMS current I=10 kA is applied leading at t=10 ms to an amount of copper equal to 0.55 mg. The vapours change the plasma properties mainly the electrical conductivity and radiation and so the plasma behaviour. At time t=5 ms the electrode erosion leads to a copper plasma. This simple case shows the necessity to well consider the copper erosion in plasma modelling as in High Voltage Circuit Breaker (HVCB) where higher current are considered

Spectroscopic Study of Arc Temperature Profiles of a Switching-off Process in a Model Chamber

A model chamber was applied to emulate a switching-off process which is very similar to those in real high-voltage circuit-breakers. The arc between moved W-Cu electrodes through a PTFE nozzle in SF6 was considered. Transparent windows in the chamber wall and a slit in the nozzle enabled an optical in-vestigation of the arc cross section several milliseconds before current zero. The side-on radiance of fluo-rine atom lines has been measured. Considering rotational symmetry of the arc the corresponding radial emission coefficients have been determined. Radial temperature profiles have been obtained with uncer-tainties below 10% considering change of window transmission and optical depth of the line radiation. The experimentally determined temperature profiles are used to validate a CFD simulation of the switch-ing-off process in the model chamber

State of Art and Challenges for the Calculation of Radiative and Transport Properties of Thermal Plasmas in HVCB

This paper is focused on the state-of-the-art and challenges concerning the thermophysical properties of thermal plasmas used in numerical modelling devoted to high voltage circuit breakers. For Local Thermodynamic Equilibrium (LTE) and Non-Local Thermodynamic (NLTE) and/or Chemical Equilibrium (NLCE) plasmas, the methods used to calculate the composition, thermodynamic, transport and radiative properties are presented. A review of these last data is proposed and some comparisons are given for illustrations

We measured breakdown voltage Vb, gas temperature Tg and gas density N with the corresponding critical electric field Ecr/N in hot dissociated mixtures initially involving SF6, C2F4 and Cu highly diluted in argon. These gas mixtures are heated by a microwave source generating a plasma flame that ablates Cu atoms from a thin copper filament placed inside the cell of the hot gas conditioning. Densities of Ar, SF6 and C2F4 are controlled by flowmeters while density of ablated Cu is estimated from optical emission spectroscopy, that is also used for Tg and N estimation. The measured Ecr/N data in the considered experimental cases of gas temperatures and mixture compositions are needed to analyze the sets of the collision cross sections of species involved in hot dissociated SF6 (11 species), C2F4 (19 species), crossed species (2 species) and Copper byproducts (5 species). The sets of collision cross sections of SF6/C2F4 byproducts were taken from a previous work and those of copper byproducts are fitted and validated in the present work. Then, the sets of collision cross sections of all species are considered without argon in some hot specific SF6/C2F4/Cu mixtures to analyze the effect of more particularly Copper on Ecr/N for large ranges of Tg (up to 4000K) at a given gas pressure using a rigorous multi-term solution of Boltzmann equation for electron energy distribution function while calculations based on thermodynamic equilibrium formalisms of hot gas composition for species proportions.

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Breakdown electric fields in dissociated hot gas mixtures of sulfur hexafluoride including teflon: Calculations with experimental validations and utilization in fluid dynamics arc simulations

International audienceMeasurements of breakdown voltage Vb, gas temperature Tg and density N and the associated critical electric field Ecr/N are performed in hot dissociated SF6 highly diluted in argon and in hot dissociated SF6 mixed with PTFE (Polytetrafluoroethylene or C2F4) also highly diluted in argon. Gases are heated using a microwave source and optical emission spectroscopy is used for measurements of Tg and N while Vb is measured from a specific inter-electrode arrangement placed inside of the cell of the hot gas conditioning. The experimental Ecr/N data in the numerous considered cases of gas temperatures and compositions have been used to evaluate and validate the sets of the collision cross sections of the 11 species involved in hot dissociated SF6 (i.e. SF6, SF5, SF4, S2F2, SF3, SF2, SF, S2, F2, F, S) , the 13 additional species involved either in hot C2F4 or CF4 (C2F6, C2F4, C2F2, CF4, CF3, CF2, CF, F2, F and carbon species as C, C2, C3, C4) and also the 2 further species (CS and CS2) present only in the considered mixtures SF6+C2F4. The fitted sets of collision cross sections of all these 26 species are then used without argon dilution in hot SF6 and hot SF6+C2F4 mixtures to calculate and to analyze the Ecr/N data obtained for a wide range of gas temperature (up to 4000K) and gas pressure (8 bar and more) using a rigorous multi-term solution of Boltzmann equation for electron energy distribution function and standard calculations of hot gas composition for the species proportions. Such Ecr/N data have been then successfully used to evaluate from a CFD (Computational Fluid Dynamics) model the switching capacity at terminal fault from a coupled simulation of the electrostatic field and the hot gas flow after current zero

Critical electric fields in hot SF 6 , C 2 F 4 and Cu mixtures: Calculations with experimental validations for gas circuit breaker applications

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