LV cable in derating factor for cable in a brick trench

[Muhammad A]

Hi All.I want to lay multicore PVC aluminium cable in a trench 300mm wide and 450mm deep( bricks used)This trench will have supports to support cable and this trench will have cover at top only means 300mm x 450mm area will be hollow throughout and only covers( may be concrete slabs) at top .What derating factors will be applied for ths .load is 220Amps and 400V three phase.

 

[7anoter4]

See: IEC 60364-5-52 Table 52-3 item 50 and Table A.52-4 (52-C3) – Current-carrying capacities in amperes for methods of installation in table A.52-1 (52-B1) –PVC insulation/three loaded conductors/copper or aluminium –.And in a case there are more than 1 circuit see:
Table A.52-17 (52-E1) – Reduction factors for groups of more than one circuit or of more than one multi-core cable to be used with current carrying capacities of tables A.52-2 (52-C1) to A.52-13 (52-C12).

 

[Muhammad A]

Thankyou for guidance.