Testing and Modeling of Low Current Arc in Free Air

As single-phase-earth fault occurred in low current earthed system, arc self-extinguishing characteristics caused by the short-circuit currents influence the safety and the reliability of Grid working. A simulated test circuit is adopted in the paper, to discuss arcing characteristics on low current system by abundant tests. Based on these achieved test data, taking the movement of long AC arc into account to get arc factual length, an arc dynamic conductance model at low current is setup, promoting the equivalent circuit and arc self-extinction criterion of arc model. Single-phase-earth arcing fault on 10 kV distribution network is computed and analyzed as an example by the simulation program, those results, as arc length, arc waveforms and arc duration times, conform test phenomenon. With the studies, arc self-extinction mechanism at low current in free air has been completed further to expose the physical nature of air arc, and proposing a practical arc model to guide the engineering application.