The obtained results imply that the hydrophobicity in the
surge arrester without polluted layer helped to avoid surface
discharges on its surface and consequently, a small amount
of leakage current pulses as shown in Fig. 3d, compared to
the other tested equipments. In the range of current pulses
higher than 260 mA, the accumulated pulses are practically
zero; consequently, the flashover probability under these
conditions is very low. The number of pulses recorded for
the 50–120 mA and 120–250 mA ranges indicates that
degradation in the insulation because of surface discharges
(pollution) may be insignificant in this case.
As the leakage current interval increases (Fig. 3), the
current peak’s behaviour is similar in both bushings and in
the surge arrester with pollutant layer. In the ranges from
50–120 to 320–380 mA, the number of pulses decreases
as the magnitude of current peaks increases. In the
380–440 mA range, the number of peaks increases slightly
and then diminishes to the 440–500 mA range. After this
range, the number of peaks tends to increase from one
range to another starting at 440 mA. According to results
obtained in other research projects [2, 35, 36], it has been
observed that polymeric insulation is aged mainly by lowenergy
surface discharges. Hence, by considering the
number of pulses recorded in the 50–120 and 120–250 mA
intervals, it can be said that these leakage current peaks
accelerate the ageing of the non-ceramic components.
According to Figs. 3a and b, the non-solid layer of
contaminant on sample 1 caused the increase of leakage