Statistical properties of the distribution of bow-tie trees in a field aged HV cable

Recent observations show radial and azimuthal variation of the density and residual stress of the XLPE insulation of HV cables in the vicinity of the inner conductor [1]. In order to investigate possible effects of such stress on bow-tie tree growth, the probability of bow-tie tree occurrence, in a 25 kV distribution cable which had been in service for 18 years, were investigated as a function of a) radial position, b) azimuthal position and c) the wing size.<>