Electrical tree inhibition by voltage stabilizers

Electrical treeing is one of the main degradation mechanisms in polymer dielectrics at highly divergent electric fields and can, if initiated, cause dielectric breakdown as soon as an electrical tree channel has bridged the insulation. One way of increasing resistance to electrical treeing is the addition of certain organic additives such as polycyclic aromatic compounds or benzophenone-like structures. These additives act as voltage stabilizers that are believed to capture high energy electrons and dissipate their energy, preventing degradation of the polymer matrix by the impact of “hot electrons”. In this study, a benzil type compound is evaluated as voltage stabilizer in a superclean cross-linked polyethylene compound used for high voltage cable applications. The stabilizing effect of the additives is measured using test objects of wire-plane electrode geometry in ramped AC voltage experiments. For determining tree initiation conditions, optical detection is used and correlated to voltage measurements. In this way, the initiation voltage of each single tree is determined. Results show that the investigated voltage stabilizer raises the electrical tree inception level significantly. The stabilizing effect is dependent on voltage ramp rate and using a lower ramp rate results in a more pronounced effect of the stabilizer.