IEC 60502-1:2021 pdf free download – Power cables with extruded insulation and their accessories for rated voltagesfrom 1 kV (Um =1,2 kV) up to 30 kV(Um = 36 kV)
7.4.2 Cables having only a collective metal layer (see Clause 8)
Cables shall have an inner covering over the laid-up cores.The inner covering and fillers shallcomply with 7.2 and shall be non-hygroscopic.
7.4.3 Cables having a metal layer over each individual core (see Clause 9)The metal layers of the individual cores shall be in contact with each other.
Cables with an additional collective metal layer (see Clause 8) of the same material as theunderlying individual metal layers shall have an inner covering over the laid-up cores. The innercovering and fillers shall comply with 7.2 and shall be non-hygroscopic.
When the underlying individual metal layers and the collective metal layer are of differentmaterials，they shall be separated by an extruded sheath of one of the materials specifiedin 13.2.For lead-sheathed cables, the separation from the underlying individual metal layersmay be obtained by an inner covering in accordance with 7.2.
For cables having neither armour， nor concentric conductor，nor other collective metal layer(see Clause 8), the inner covering may be omitted，provided the outer shape of the cableremains practically circular. The oversheath may penetrate into the interstices of the cores,except in the case of thermoplastic oversheaths over circular cores exceeding 10 mm2. lf,however, an inner covering is applied, its thickness need not comply with 7.2.3 nor 7.2.4.
For flat armour wires and fictitious diameters under the armour greater than 15 mm, the nominalthickness of the flat steel wire shall be 0,8 mm. Cables with fictitious diameters under thearmour up to and including 15 mm shall not be armoured with flat wires.
12.6 Round or flat wire armour
The wire armour shall be closed, i.e. with a minimum gap between adjacent wires.An openhelix consisting of galvanized steel tape with a nominal thickness of at least 0,3 mm may beprovided over a flat steel wire armour and over a round steel wire armour，if necessary.Tolerances on this steel tape shall comply with 16.7.3.
12.7Double tape armour
When a tape armour and an inner covering as specified in 7.2 are used, the inner covering shallbe reinforced by a taped bedding.The approximate thickness of the inner covering and theadditional taped bedding shall be as given in 7.2 and the combined approximate thickness shallbe increased by 0,5 mm if the armour tape thickness is 0,2 mm, and increased by 0,8 mm if thearmour tape thickness is more than 0,2 mm.
lf a separation sheath is required or if the inner covering is extruded and satisfies therequirements of 12.3.3, the additional taped bedding is not required.
The tape armour shall be applied helically in two layers so that the outer tape is approximatelycentral over the gap of the inner tape.The gap between adjacent turns of each tape shall notexceed 50 % of the width of the tape.