Fire probability risk ranking of vegetation species in vegetation high impedance faults

Abstract

This work presents an analytical approach into fire-risk ranking of vegetation species during VeHIFs. One prior approach to such a fire risk assessment involved the consideration of the amount, size, and temperature of embers falling from branches. This work proposes a purely analytical methodology based on the analysis of average/maximum magnitudes of odd-harmonics current signatures released from species during VeHIF events. This analytical approach relates to the premise that emission of fault signatures is dependent on the ignition stages that a species experiences, while subject to a conductor-to-tree contacts. High-risk species experience volatile fault currents, with volatility being a sign of physical charring, subsequently leading to heightened ember formation. This volatility in the fault currents of high-risk species also results in higher levels of odd-harmonic current signatures. The temporal growth rate of odd-harmonics is the second critical factor, with elevated fire-risk observed in slow temporal fault current growth species. This is linked to the fact that when the fault current growth is slow, this elevates the fire-risk in terms of increased times for traditional over-current methods to clear the fault. Salix and S. Molle have been determined as the highest and lowest risk species respectively. Findings are compatible with observatory analysis on ember formation.