This standard concerns exclusively the operation in permanent regime of cables insulated from all voltages in alternating current and voltages up to 5 kV inclusive in direct current, buried directly in the ground, in conduits, pipelines or in steel tubes, as well as cables laid outdoors. "Steady regime" is understood as the continuous circulation of a constant current intensity (load factor 100%) just sufficient to asymptotically reach the maximum temperature of the conductor, assuming that the environmental conditions remain constant. The proposed formulas are essentially literal and leave the free choice of certain important parameters. The latter can be divided into three groups:
——the parameters, linked to the construction of the cable (for example, the thermal resistance of the insulator), for which representative values have been chosen, based on published works;
——the parameters related to the conditions of the surrounding environment, which can vary considerably and whose choice depends on the country where the cables are used or must be used;
——the parameters that result from an agreement between the manufacturer and the user and that imply a service safety margin (for example, the maximum temperature of the conductor).