Method and armoured cable for transporting high voltage alternate current

Method for improving the performances of an armoured cable (10) having a cable length L and comprising a plurality of cores (12) stranded together according to a core stranding direction (21), each core (12) comprising an electric conductor (12a) having a cross section area X;

• and an armour (16) surrounding the plurality of cores (12), the armour (16) comprising a layer of metal wires (16a) helically wound around the cores (12) according to an armour winding direction (22);
• the armoured cable (10) having losses when an alternate current I is transported, said losses determining a maximum allowable working conductor temperature θ, the method comprising the steps of:
• reducing the losses by building the armoured cable (10) such that the at least one of core stranding direction (21) and the armour winding direction (22) is recurrently reversed along the cable length L so that the armoured cable (10) comprises unilay sections (102) along the cable length L where the core stranding direction (21) and the armour winding direction (22) are the same;
• building the armoured cable (10) with a reduced value of the cross section area X of each electric conductor (12a), as determined by the value of the reduced losses, and/or
• rating the armoured cable (10) at the maximum allowable working conductor temperature θ to transport said alternate current I with an increased value, as determined by the value of the reduced losses.

A method for manufacturing an armoured cable (10) with a cable length L having losses when an alternate current I is transported, said losses determining a rating of the cable at maximum allowable conductor temperature θ, comprising the steps of:

• stranding a plurality of cores (12) together according to a core stranding direction (21), each core (12) comprising an electric conductor (12a) having a cross section area X;
• surrounding the plurality of cores (12) by helically winding an armour (16) comprising a layer of metal wires (16a) around the plurality of cores (12) according to an armour winding direction (22);
• wherein at least one of the core stranding direction (21) and the armour winding direction (22) is recurrently reversed along the cable length L so that the armoured cable (10) comprises unilay sections (102) along the cable length where the core stranding direction (21) and the armour winding direction (22) are the same;
• and
• wherein the cross section area X of each electric conductor (12a) is reduced and/or the rating of the cable at the maximum allowable working conductor temperature θ is increased, compared to a cable wherein the core stranding direction (21) and armour winding direction (22) are contralay along the cable length L.