A tentative tracking model based on energy balance criteria

A tentative mathematical model is described for estimating the time required for tracking to occur in rotating wheel water-spray or dip tests on polymeric insulating materials. The model is based on the energy balance criterion. In the derivation of the model, the required time for tracking to occur is treated as a function of the geometrical dimensions, the thermal characteristics and the volume and surface conductivities of the specimen. It is also considered to be dependent upon the applied voltage, wheel speed as well as the time required for arcing to occur, the lischarge activity and the number of dry bands formed upon the surface of the specimen. The validity of the model is assessed, using experimental data obtained with epoxy fibre glass composite specimens; reasonable agreement is found between the experimental results and the calculated values.