  Over the past decade, significant progress has been made in the field of loss
and rating calculations for armoured three-core cables. This development was
prompted by an industry realization that the applicable international standards
often overestimate losses, leading to unnecessarily bulky and more expensive
cables. Starting with first-principles, this paper presents an accurate
analytical formula for armour losses in three-core cables. The formula has
undergone rigorous validation against 3D Finite Element Analysis (FEA) and
demonstrate excellent accuracy. In the specific cases examined, the largest
deviation from FEA results in terms of armour loss is approximately 2.4 percent
for fully armoured cables. Although this study specifically focuses on armour
losses, it establishes the groundwork for precise loss calculations in armoured
three-core cables, including the conductor and screen losses. And the work
presented here formed the basis for the complete loss calculations presented in
the CIGRE Technical Brochure 908.
