Thermal circuit model of DC submarine cable considering the influence of seawater property variations

Abstract

The IEC 60287 standard, when calculating the steady-state current-carrying of DC submarine cables, does not take into account the influence of seawater property variations on changing the heat transfer efficiency of seawater, thereby affecting the current-carrying capacity of the cable. resulting in deviations in the calculated ampacity results. This paper considers the influence of seawater heat transfer characteristics on cable heat dissipation efficiency based on heat transfer theory, and Proposes an improved thermal circuit model for submarine DC cables that takes into account variations in seawater properties. Taking the example of a 160 kV submarine XLPE cable, the current-carrying capacity results of the improved model have an error of no more than 1.9 % compared to finite element simulation results. Under identical environmental conditions, the maximum deviation between the improved model and the IEC thermal circuit model is 123A, confirming the necessity of considering variations in seawater properties in the improved thermal circuit model. The seawater property variations studied in this paper include changes in seawater temperature, salinity, and pressure. If the impact of seawater property variations on submarine cable current-carrying capacity is not considered, the obtained current-carrying capacity results are higher, with a maximum error of 5.5 %. Among these variations, temperature has the most significant impact, with an error reaching 3.3 %, while salinity and pressure have relatively smaller impacts, with errors of 1.1 % each.