Romaric Landfried

Arcing fault in aircraft distribution network

With the rising demand for electrical energy in an aircraft and the increase in operating voltages of the electrical distribution networks, the probability of occurrence of an arc fault is also increased. New protection devices such as arc fault detectors are now integrated in the network to break the circuit in case of an arcing event. To determine the optimum location of these protection devices, a simplified electrical distribution network is modelled. This network distributes power to common aircraft loads. An electric arc model for circuits as presented in a previous work is then placed at various locations in the network. Simulations of normal arcing and arcing faults are given for each load. Finally, the modification of the spectral content of the network currents is studied to deduce the optimum locations of arc fault protection in the network.

Temperature Measurement of Tungsten Electrode Surface at Electric Arc Extinction in Air–Power Flux Estimation

This paper deals with temperature measurements of the surface of tungsten electrodes submitted to electric arcs in nonstationary regimes in air at atmospheric pressure and with the estimation of the power and power density brought by electric arcs to the electrodes. Temperature measurements are proposed for tungsten anodes and cathodes for current intensity of ~30 A and duration of 3 ms. The temperature of the electrode surface at the instant the arc extinguishes is estimated in both electrode polarities. These experimental results are used in a model to estimate the power and the power density brought to the tungsten electrode surface by electric arcs. We found that the power surface density brought by electric arcs to the electrodes was in the range 1. × 109-1.5 × 109 W/m2 in the case of anodes and in the range 1.3×109-1.9×109 W/m2 in the case of cathodes. It has also been found that reactions of tungsten oxidation had to be considered to explain the high values obtained for the power brought to the electrodes.

Parametric Study of the Current–Voltage Characteristics of a 100-mbar DC Discharge in Argon: From the Diffuse Glow Discharge to the Arc Regime

The aim of this paper is to investigate the glow discharge in its diffuse and filamentary regime, and to study its transition to arc in argon at 100 mbar. The structure of the discharge is observed in correlation with its electrical signals in both static and in dynamic modes. Glow discharges were identified with a positive column that can be fully diffuse, fully filamentary, or a mix of the two with the filamentary part of the column always attached to the anode. Spontaneous transitions between glow discharges and arcs have also been observed and their dynamics are studied. Using high-speed imaging, the transition between glow and arc discharge was identified as the occurrence of two distinct phenomena: a propagation mechanism in the positive column and a constriction of the cathode root. An evaluation of the duration of each phenomenon as a function of electrode gap and current intensity was obtained. The duration of the constriction of the cathode root is found to be on the order of tens of nanoseconds and the duration of the propagation mechanism in the range 50–550 ns.

Experimental assessment of the surface temperature of copper electrodes submitted to an electric arc in air at atmospheric pressure

This paper concerns the assessment of the surface temperature of copper electrodes submitted to an electric arc in a non stationary regime in air. An infrared camera is used to measure the decrease of the temperature surface just after a controlled and very fast arc extinction. In the first part, the experimental method is described. In the second part, results are presented for 60–70 A with an electric arc duration in the range 3–4 ms. The temperature decrease after the arc extinction allows to reach an assessment of the surface temperature just at the arc switching off. In the present experimental conditions the mean temperatures reached for copper cathodes and anodes are in the range 750–850°C.