Hi guys(adsbygoogle = window.adsbygoogle || []).push({});

I received electrical drawings for a construction project as a part of invitation for tendering.

The project includes a number of SMDBs connected to two MDBs which are connected to two transformers. Looking at the schematic design, I found that a SMDB is connected to one of the two MDBs using 4 cables of 4 cores of 240 and for each cable there is 120mm2 ECC.

4x (4CX240mm2 XLPE/SWA/PVC+1CX120mm2 ECC)

The total connected load of the SMDB is 618 KW and it is 3 phase load, 400 V and Power Factor =0.8 . The distance between the SMDB and the MDB is 110 meters.

My question is how on earth did he find this result? How did he make the cable size calculation? Be aware that the regulation used here is BS 7671.

Many thanks in advance

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# Cable size for big loads

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