Avibrational mechanical stress will be set up in a solid insulating material subject to
partial discharge stressing under normalACoperating conditions due to the interaction
of trapped charge in the solid matrix from the discharge interacting with the applied
AC electric stress field. In addition, trapped charged particles of similar polarity will
be repelled from each other and dissimilar charges attracted to each other, again
resulting in a local mechanical stress within the solid matrix. There will also be
a mechanical stress resulting from the impact of larger particles at the discharging
surface depending on the mass number and collision velocities of these particles. It is
unlikely that this will have sufficient energy to cause fracture, as the shock wave is
likely only to have energies of the order of 10−12 J [8]. However, once again the
synergetic effects of such a process cannot be dismissed.