This contribution is focused on the application of laboratory dielectric losses measurements to the insulation of service aged oil-impregnated HV power cables. The goal is to investigate the dependence between the electrical and temperature stresses to impregnated paper insulation at different aging stages. By means of laboratory tests with differential transformer testing circuit on aged paper samples the following has been investigated: ldr The influence of voltage stress on tan delta measured on samples taken from different parts of cable insulation: close to conductor, middle part and outer part. ldrThe behaviour of dielectric losses as a function of test voltage and temperature for paper samples in different age condition.@en