power cable

There is no one real formula of this. See the gazillions of CR4 threads on cable sizing.

British Standard 7671 again.

Contact the British Standards Institution. There's so many copies of BS7671 there that there's a sales drive on just to get rid of them.

It seems complicated, however, I might just put it together for you :)

Load of 10 motors of 10KW each = 100KW

Load of 7 motors of 15KW each = 105KW

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Total Load (not including any safety factor) = 205KW

Total Length = 320 meters

Assuming voltage drop allowed = 2.5%

Max. acceptable voltage drop (Vd) = 2.5% (415) = 10.375v

I = (205 X 1000)/(1.73 X 415 X 0.8) = 356.7A

Using the following formula:

Formula Vd = mV x I x L or mV = Vd x 1000

1000 I x L

where Vd = maximum acceptable volt drop (in volts)

I = current per phase (in amps)

mV = appropriate volt drop (in mV/amp/metre)

L = route length (in metres)

Once you come up with mV figure, then look up for the manufacturer list of four core

xlpe cable.

After studying the table to find a voltage drop value equal to, or less than the calculated one above. Then you could select the cable size in the same row in the table....

Your breaker size would be of 630A MCCB, depending on the sizing. Hoping that would help ya :)