IEC 60502-1-2021 pdf Power cables with extruded insulation and their accessories for rated voltages from 1 kV (U m = 1,2 kV) up to 30 kV (U m = 36 kV) – Part 1: Cables for rated voltages of 1 kV (U m = 1,2 kV) and 3 kV (U m = 3,6 kV)

The temperatures in Table 3 are based on the intrinsic properties of the insulating materials. It is important to take into account other factors when using these values for the calculation of current ratings. For example, in normal operation, if a cable directly buried in the ground is operated under continuous load (100 % load factor) at the maximum conductor temperature shown in Table 3, the thermal resistivity of the soil surrounding the cable may, in the course of time, increase from its original value as a result of drying-out processes. As a consequence, the conductor temperature may greatly exceed the maximum value. If such operating conditions are foreseen, adequate provisions shall be made. For guidance on the short-circuit temperatures, reference shall be made to IEC 60724. 4.3 Sheathing compounds The types of sheathing compound covered by this document are listed in Table 4, together with their abbreviated designations. The maximum conductor temperatures for the different types of sheathing compound covered by this document are given in Table 4.
7.4 Cables with rated voltage 1,8/3 (3,6) kV 7.4.1 General Cables with a rated voltage of 1,8/3 (3,6) kV shall have a metal layer surrounding the cores either individually or collectively. 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 shall comply 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 the underlying individual metal layers shall have an inner covering over the laid-up cores. The inner covering 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 different materials, they shall be separated by an extruded sheath of one of the materials specified in 13.2. For lead-sheathed cables, the separation from the underlying individual metal layers may 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 cable remains practically circular. The oversheath may penetrate into the interstices of the cores, except in the case of thermoplastic oversheaths over circular cores exceeding 10 mm 2 . If, however, an inner covering is applied, its thickness need not comply with 7.2.3 nor 7.2.4.