Fig. 7

Test-measurements of the FOVmin on the porcelain and glass insulators with fresh volcanic ash from Cotopaxi-2015 and Tungurahua-2016 eruptions based on six contamination scenarios. The asterisks point out when the FOVmin occurred in each test. Note that scenarios 1, 2 and 3 have a different vertical scale than scenarios 4, 5 and 6. The red dashed line depicts the tolerance value at 36 kV that the insulator can withstand under moist conditions and no particle contamination