Fire Probability Risk Ranking of Vegetation Species in Vegetation High Impedance Faults

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 firerisk 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.