Modelling of DC arcs for photovoltaic system faults

Arc faults in a PV system are difficult to study using models developed for conventional power sources mainly due to non-linear behavior of PV current and its dependence on external factors such as irradiance, shading and maximum power tracking controls. This paper presents a unique model derived from fundamentals of Mayr and Cassie arc models and introducing a hyperbolic tangent function to approximate arc current at near zero gap. Arc impedance widely changes with heat dissipated through arcs periphery. Unique feature of the proposed model is that it takes into account this change of impedance with time which could be used to analyze arcs with changing lengths due to movements of current carrying elements. A test bench has been built with adjustable gap between two electrodes to conduct experiments. Both experimental results and simulation outcomes are presented to verify the proposed model.