Influence of volcanic ash contamination on the flashover voltage of HVAC outdoor suspension insulators

High voltage station and line insulators are vulnerable to volcanic ash-induced flashover, yet little quantitative data exists on the environmental, volcanological and electrical parameters most influential in reducing their flashover voltage. This paper presents the results from clean-fog rapid flashover tests for 5 different suspension insulators of ceramic, non-ceramic, or RTV-coated design under different environmental and volcanic ash contamination scenarios. Results suggest that moderate accumulations (up to 3 mm) of volcanic ash can accumulate on insulator surfaces without critically reducing the flashover voltage, provided >40% of the creepage distance remains clean and dry. Composite polymer insulators have higher dielectric strength than ceramic equivalents under light to heavy pollution severities, however, all insulators tested here perform comparably when critically contaminated (i.e. both top and bottom surfaces coated in ash). Based on these and other findings, some basic discussion of optimal insulator selection in ashy environments is provided.