FEM-based Arrhenius modeling of the thermal effects of a heating pipeline and pavements on underground power cables

Abstract

It is well-known that, in thermal aging management of underground power cables, analytical Arrhenius models can include the thermal effect of a heating pipeline on the lifespan of power cables through a rise in the soil temperature and an appropriate ampacity de-rating factor. However, the thermal effect of a pavement on the lifespan of power cables installed below that pavement cannot be taken into account using any de-rating factor. Accordingly, this paper proposes FEM-based Arrhenius models to analyze the thermal effects of one heating pipeline and several different types of pavements on the thermal lifespan of an underground line of 110 kV consisting of cables with cross-linked polyethylene (XLPE) insulation. Each proposed Arrhenius model is created using both IEC 60287 and IEC TR 62095, as well as combining the traditional Arrhenius model with an appropriate FEM-based steady-state thermal model. An experimental background consisting of the existing thermal aging tests with XLPE insulation is also used. Different pavements are represented by different values of thermal and surface radiation properties, namely: thermal conductivity, solar absorptivity, and thermal emissivity. The pavement surface radiation properties are specified within the frames of the most unfavorable summer conditions, and the most common winter conditions. Moreover, different distances between the 110 kV cables and the heating pipeline are considered. Finally, it is found that: the considered thermal effects can shorten the expected total service lifespan of the 110 kV cables in the area adjacent to the heating pipeline by up to 297.5 h; the pavement surface radiation properties do not affect the consumption of total thermal lifespan; as well as the largest consumption of total thermal lifespan occurs when the 110 kV cables are at the smallest distance from the heating pipeline.