Abstract-It is widely recognized that one of the major problems responsible for unscheduled interruptions is related to the degradation of power cables insulation. The water tree effect emerges as an important cause for the deterioration of their insulation layer. In this context, the loss current technique is a suitable method for investigating slight degradation, since the cable degradation by water tree gives rise to harmonics components in the loss current. This paper presents an analysis of the influence of the length of the water-tree, the voltage stress and the frequency in the values of various parameters that has been used to evaluate, predict, and indicate the operational status of operating power cables. The procedure aims to estimate the parameters of insulation deterioration from the measurement of the supply voltage and the leakage current that flows through the insulation carried out in hot-line cables without interrupting the service.