In this research work the effect of internal strain on electrical tree growth has been revealed in
clear polyester. Strain was introduced in the specimen by the introduction of particles like aluminium
oxide, polytetroflouroethylene (PTFE) and glass beads in a clear polyester resin C. Aluminium oxide
particles of size 105mm, PTFE 675mm and glass beads of 1mm were tested. These materials were employed
in a clear polyester resin thus making a barrier. The batch of 20 annealed, un-annealed and oiled specimens
of each material were tested. Using aluminium oxide, PTFE and glass beads made detailed observation of
the interaction between advancing tree channels and the particles. The clear interaction of tree channel
between dense barrier of aluminium oxide and PTFE was impossible but glass beads being transparent in
nature allowing progress of the tree through barrier to be carefully studied. Strain were removed or relaxed
by annealing the specimens and work of adhesion reduced by oiling the specimens.