Characterising electrical trees in nanocomposite epoxy-resin using partial discharge detection methods

摘要

Modern polymer based solid electrical insulation technologies, whilst highlyudoptimal for their function, have been shown to have a major udaw: suscep-udtibility to electrical treeing failure mode. This dissertation investigates theudpossibility of using Partial Discharge (PD) detection techniques to monitorudand characterise electrical trees in nanocomposite epoxy insulation. The ex-udperimentation is done by creating highly divergent electric stress in nanocom-udposite samples and monitoring PD magnitudes over time until failure. Fur-udthermore, a remote monitoring system was designed to allow for constantudmonitoring from anywhere with an internet connection. The experimen-udtal results revealed several interesting ndings. Electrical trees in un lledudinsulation behave di erently from those in nanocomposite insulation. Theudelectrical trees that form in un lled epoxy are of bush/branch type with theudcorresponding PDs comprising of both big (greater than 10 pC) and smallud(less than 10 pC) pulses throughout the lifetime of the tree. In nanodielectricsudhowever, the PD magnitudes are generally smaller than in the un lled dielec-udtric. Moreover the PD patterns evolve through distinct phases as the treesudpropagate from inception to complete failure. These distinct phases showudnew behaviour not seen in un lled insulation, with phases of complete si-udlence and some displaying patterns similar to corona. The resulting patternsudare analysed and auto-classi ed, using a program written for this purpose,udbefore being used to develop a model to explain the observed behaviour.