Pyroclastics and power: Quantifying the Vulnerability of High Voltage Electrical Distribution Systems Exposed to Volcanic Ashfall Hazards
Wardman, J., Wilson, T., Cole, J., Bodger P., Johnston D.
High voltage electrical transmission networks are vulnerable to interruption during explosive volcanic eruptions. Several problems arise from high voltage transmission equipment exposed to volcanic ashfall hazards. Depending on variable conditions, the most common problems arise from supply outages due to insulator ‘flashover’, controlled outages during ash cleaning, line breakage and tower collapse and the breakdown of air conditioning/ cooling systems/ diesel generators in substations and other types of housing caused by air intake blockage and corrosion.
While ample anecdotal accounts and information exists (Johnston, 1997; Tuck et al. 1992; Narajo and Stern, 1998; Durand et al. 2001), little quantitative data has been gained from research of this kind. Research at the University of Canterbury is currently investigating the properties most significant in causing the electrical breakdown of insulators a phenomenon better known as ‘flashover.’
Dry volcanic ash is highly resistant to the flow of electricity, however this resistance drops rapidly with increasing input from influential parameters. The major parameters being explored include grain size, ionic content, moisture content, and compaction. Results show that under testing conditions electrical resistance is minimal with increasing grain size, ionic content, moisture content and compaction rates. Ash composition together with the type of ions made available from attached soluble salts have proven to be inconsequential while other controlling factors are undergoing further analysis.
Future endeavours include a characterisation of insulator adherence properties subsequently followed by live testing of high voltage insulators exposed to volcanic ashfall. This project will ultimately look to resolve some of the uncertainty involved in defining the parameters that allude to volcanic ash being a major hazard to high voltage electrical distribution systems.
Control chamber for HV testing. |
Flashover on an insulator string |
