Electrical-Thermal Rating of High-Voltage Cables via EMTP Coupled Modelling

The increasing adoption of high-voltage underground cable systems for power transmission, which is mainly driven by environmental concerns and land use restrictions, is changing the way Transmission System Operators approach network design and operational planning. As these insulated systems become more prevalent, particularly in urban or environmentally sensitive areas, it becomes crucial to accurately determine the cable current-carrying capability, or ampacity, under a wide range of realistic operating conditions. Traditional rating methodologies, including those defined by the IEC standards, tend to rely on fixed assumptions, such as steady ambient temperature and homogeneous soil thermal resistivity, while neglecting realistic sheath currents values coming from the actual three-dimensional cable laying sections sequence. These simplifications are often adopted for convenience and standardization but can result in either overly conservative design margins or unintended thermal overload risks. To address these limitations, this paper presents the development of an advanced simulation framework aimed at assessing the rating of high-voltage cable lines both under steady state and dynamic conditions. The core of the methodology is a multi-domain modelling tool built in an