Modelling of sparking contacts for hazardous area applications

Abstract

An understanding of transient contact sparks and how they interact with electrical systems is of critical importance to hazardous area applications, where such sparks are at risk of igniting flammable atmospheres. Hazardous area electrical systems are distinguished from more typical applications of spark modelling by their low voltages and currents. This paper applies an empirical, quasi-static modelling approach to such spark discharges. The use of a classical parametrised empirical model is proposed, and justified with a qualitative treatment of the underlying physics. Parameter values for the model are calculated by studying sparks with constant length and constant current respectively, and then combining the observed trends into the proposed model. The model, is then validated against experimental data obtained from sparks with time varying current and length. The relevance of dynamics arising from energy storage in the arc column is also considered, identifying the situations where a quasi-static approach is sufficient. Finally, methods for determining the thermal output of the spark, the ultimate goal of spark modelling in hazardous area applications, are discussed.