In this study the laboratory aged safety related cables were investigated with return voltage measurements. The cable samples were received from the International Atomic Energy Agency Coordinated Research Project and the voltage response measurements were carried out in the BME. The samples were aged by elevated temperature and gamma irradiation. I tried to find correlation between ageing and the parameters of return voltage measurement. At the beginning in my study, there is a literature review about the construction and insulation of cables, which are used in nuclear power plants and the enviromental stressors and return voltage response method also introduced.
In the experimental stage four type of cable were examined: two of them have type EPR insulation the others have XLPO and PEEK. In the investigation the optimal discharging time for voltage response measurement was found for monitoring ageing cables. Then I examined slope of return voltage as the function of short circuit times. I observed the measured values are fitting on a straight line or curves with one cut off point. After the examination it can be stated good ageing marker could be the curves slope, or the difference between the slopes of straigth lines before and after the cut of point or the slope after the cut of point.