Electrical treeing is oneof the main reasons for longterm degradation of polymeric materialsused in high voltage ac applications.In this paper we report on an investigation of electrical treegrowth characteristics in XLPE samples from a commercial XLPE powercable.Electrical trees havebeengrown over a fre quencyrangefrom20Hzto500Hz and images of trees were taken usingCCDcamera without in terrup ting the application of voltage.The fractal dimension of electric treeis obtained usinga simplebox-counting technique.Contrary to our expectation it has been foundthat the fractal dimensionprior to the breakdown shows no significant change when frequencyof the applied voltage increases.Instead, the frequency accelerates tree growth rate and reducesthe time to breakdown.Anew approach for investi ating the frequency effect on trees has beendevised.In addition to looking into the fractal a nays is of tree as a whole, regions of growth arebeingsectioned to revealdifferences in terms ofgrowth rate, accumulated damage and fractaldimension.