Perspectives of temperature assessment based on wave propagation for dynamic rating of medium-voltage power cables

This paper explores the feasibility of wave propagation characteristics as means of probing the temperature of an underground power cable. It utilises the relation between wave velocity and relative permittivity. The permittivity and its temperature dependency are specific for the applied insulation materials. The investigated cable is a three-phase XLPE-insulated mediumvoltage cable with a common earth screen. Combined thermal and electromagnetic analysis is applied to account for the temperature distribution over the cable cross section. The corresponding permittivity distribution is based on the temperature dependency measured for an XLPE sample. Temperature monitoring is achieved by observing the signal transit time along the power cable. The measured variation in signal propagation velocity and attenuation, compared to model predictions, provides an estimate of the cable temperature. It is shown that a sensitivity within 2°C can be achieved for a temperature near the maximum operating value for XLPE insulation.