Study of creeping discharges propagating over epoxy resin insulators in presence of different gases and mixtures

This work shows that the discharges pattern and final length, L
_f
, of creeping discharges depend on the amplitude and polarity of the voltage, the type of gas (mixture) and pressure similarly as in the case of the materials we investigated previously. L
_f
is longer when the point is positive than when it's negative; this is likely due to the influence of space charge on the electric field. L
_f
increases quasi-linearly with the voltage; it's reduced when the pressure is increased. L
_f
is shorter in SF
₆
than in CO
₂
or N
₂
. On the other hand, the increase of SF
₆
content in SF
₆
-CO
₂
mixture leads to a significant decrease of L
_f
. Therefore the addition of small concentration of SF
₆
in a given gas mixture improve the dielectric strength of insulating structure.