Potential impacts from tephra fall to electric power systems: a review and mitigation strategies

Abstract

Modern society is highly dependent on a reliable electricity supply. During explosive volcanic eruptions, tephra contamination of power networks (systems) can compromise the reliability of supply. Outages can have significant cascading impacts for other critical infrastructure sectors and for society as a whole. This paper summarises known impacts to power systems following tephra falls since 1980. The main impacts are (1) supply outages from insulator flashover caused by tephra contamination, (2) disruption of generation facilities, (3) controlled outages during tephra cleaning, (4) abrasion and corrosion of exposed equipment and (5) line (conductor) breakage due to tephra loading. Of these impacts, insulator flashover is the most common disruption. The review highlights multiple instances of electric power systems exhibiting tolerance to tephra falls, suggesting that failure thresholds exist and should be identified to avoid future unplanned interruptions. To address this need, we have produced a fragility function that quantifies the likelihood of insulator flashover at different thicknesses of tephra. Finally, based on our review of case studies, potential mitigation strategies are summarised. Specifically, avoiding tephra-induced insulator flashover by cleaning key facilities such as generation sites and transmission and distribution substations is of critical importance in maintaining the integrity of an electric power system.

Framework for developing volcanic fragility and vulnerability functions for critical infrastructure

“…Fragility functions developed for tephra fall impacts on buildings and electrical transmission systems Zuccaro et al 2008;Wardman et al 2012b). …”

“…6a). There is one instance of IS 3 from Pacaya where above-ground pipes suffered damage from large tephra particles (Wardman et al 2012b). Because there is only one instance of pipe damage, the set of fragility functions we derive here are for individual WTPs and not pipe networks.…”

“…We are unaware of any instances of physical damage to runways or taxiways from direct tephra falls. However, at La Aurora International Airport, Guatemala, the runway was severely abraded after the 2010 eruption of Pacaya volcano as a result of tephra clean-up (Wardman et al 2012b). Therefore, we only consider the probability that an airport will be closed (effectively IS 1 ) during tephra fall.…”

Evaluating the impacts of volcanic eruptions using RiskScape

“…However, surface chemistry also matters -ash particles acquire a soluble salt coating following interaction with volcanic gases in the volcanic plume (Stewart et al, 2009). This property is important for impacts to electrical transmission lines -the reactive surface is conductive when moist, causing flashovers (short-circuits; Wardman et al, 2012). Water supplies are also vulnerable as the salt coating is soluble and so can contaminate water (Stewart et al, 2009).…”

The size range of bubbles that produce ash during explosive volcanic eruptions

“…Volcanic ash represents a significant hazard to the airline industry and operation of global commerce (Casadevall 1994;Casadevall et al 1996;Prata 2009;Durant et al 2010), water quality (Stewart et al 2006;Stewart et al 2009;Wilson et al 2010), agriculture (Cronin et al 1997;Wilson et al 2010), stability of local infrastructure (Wardman et al 2012a;2012b;Wilson et al 2012), and human health (Baxter et al 1999;Horwell et al 2003aHorwell et al , 2003bHansell et al 2006;Hincks et al 2006;Horwell and Baxter 2006). Because ash can be transported for great distances regardless of the total volume of material actually erupted, it represents one of the farthest reaching volcanic hazards.…”