Relemac Recommendations for Current Ratings:

The Current rating of power cable is defined by the maximum intensity of current (amperes) which can flow continuously through the cable, under permanent loading conditions, without any risk of damaging
the cable or deterioration of its electrical properties.

The value given in the tables are valid for one circuit in a three phase system under conditions specified. For grouping cables rating factors must be used.

The current carrying capacities mentioned in RELEMAC technical data are intended as a guide, to assist operating engineers in selecting cables for safety and reliability.

Basic assumptions and conditions of installation :-

• Max. conductor Temperature

: 90° C.

• Ambient Ground Temperature

: 30° C.

• Ambient Air Temperature

: 40° C.

• Thermal resistivity of soil

: 150°C.Cm/W

• Depth of laying (to the highest point of the cables laid direct in the ground )

   3.3,6.6 & 1 IkV Cables

: 90 cm

   22 and 33kV Cables

: 105cm

• Max. Conductor Temperature

   for Short Circuit

: 250° C.

To obtain the maximum current carrying capacity of a cable operating at different conditions from the standard, various rating factors are to be multiplied, as follows :-

I a = K x I s in amperes

I a : Current rating at actual operating conditions (amperes)