A Practical Approach to Dynamic Operation of the HVAC Submarine Cable System 'Fensfjorden' in Norway

This paper presents a methodology for dynamic operation of cable systems and the evaluation of this methodology when applied to the Fensfjorden HVAC submarine cable system in western

Norway. The work focuses on the implementation of Real-Time Thermal Rating (RTTR) using

Distributed Temperature Sensing (DTS) from the Fibre-in-Metal-Tube (FIMT) combined with a simplified thermal model of the cable.

Our thermal model is based on a steady-state version of the single-node model developed by

Thakur et al. [1]. Two free parameters, the ambient temperature and thermal loss factor, are dynamically calculated by fitting the measured DTS temperature to recent historical data. Thermal equations from IEC 60287 [2, 3] are then used to calculate the conductor temperature and ampacity. This approach is considered a reasonable simplification if load and environmental conditions do not vary too rapidly.

By continuously updating the environmental parameters of the model based on recent historical

DTS measurements, the steady-state RTTR ampacity can be calculated to account for e.g.

seasonal variations. Using one year of DTS data from Fensfjorden, we show that this steady state RTTR ampacity, recalculated based on updated conditions, can be 5-30 % higher than the conservative static ampacity, showing potential for more efficient utilisation of existing infrastructure.