Electrical treeing in high voltage cable insulation has been studied for several years and today the mostly used laboratory test set-up is the needle-plane electrode configuration. In this paper another electrode configuration is suggested. The new electrode configuration makes use of a thin tungsten wire as the electrode that delivers the high and divergent electric stress needed to initiates electrical tree growth in insulation material. Multiple electrical trees are formed during the testing, which allows determining the treeing initiation field as well as the rate of tree growth. A comparison between tree initiation conditions in samples prepared of pure LDPE and XLPE materials is shown and the data are fit by 3-parameter Weibull distributions. Electrical trees start to develop in LDPE material at lower field strength than in XLPE one and two different mechanisms of tree initiation are identified in LDPE. Improvement imposed on the treeing initiation field by adding voltage stabilizing additives to XLPE is also illustrated.
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