Electrical tree modelling in non-linear insulation

Electrical treeing is often long term. However, failure under the influence of high voltage transients can be rapid with sharp conducting inhomogeneities and protrusions becoming sources of fast growing tree structures. It has previously been demonstrated that space charge plays a dominant role in establishing tree growth. If the charge formation and concentration could be prevented so too would localised breakdown and hence tree growth. The inclusion of non-linear fillers has also previously been shown to introduce nonlinear characteristics to the filled material so that at high electric fields the composite material exhibits a degree of conductivity whilst maintaining good insulating properties at low fields. Established fractal models of the treeing phenomenon have been modified to take into account the non-linear characteristics of such filled materials. From this mathematical model simulated trees have been produced which replicate those occurring experimentally for unfilled polyester resin and for this resin filled with a linear and a non-linear filler.