cable sizing for 400a 175m 4 core

[matt12321]

hey,

ive been asked to work out a cable size for someone and not sure on the sizing for the amps. the information received is that its to be armoured, 4 core and the distance is 175m and needs to carry 400amps. is there a cable big enough or will they have to run two in parallel.

thanks

 

[Guest123]

Plenty of cables capable of carrying 400A.

I've just installed supplies to some roof mounted chillers rated at 400A at a university, a shorter run than yours granted, but they were 150mm 4c.

Obviously you need to factor in all the applicable cable factors, installation method, nature of load, temp, grouping etc etc to arrive at the size you need but a single cable will suffice IMO.

 

[Darkwood]

As with everyone asking these questions... you've supplied a quarter of the info needed, how can we even start to weigh it up if we dont know install methods, ambient temp, nature of the load (i.e. high inertia motor) etc etc ..... if you havent be given the info then i suggest you ask alot of questions about the install before posting them our way....

 

[matt12321]

buried direct, no grouping, ambient temp 30, soil res 2.5

 

[Guest123]

buried direct, no grouping, ambient temp 30, soil res 2.5

I was just about to add, the only problem you might have is if the cable is buried directly in the ground.

I think you may need parallel conductors for this.

 

[Bobster]

What are you using to protect the cable?

 

[topquark]

As above plus is it single or three phase supply? If three phase is that 400A current requirement per phase?

 

[matt12321]

300 a breaker i think, 3 phase supply and 400a across all 3 phases

 

[topquark]

Three phase + neutral + earth .... no bonding to be done or are you hoping to use the armour for earth?

 

[matt12321]

three phase and neutral and running a separate earth and no, no bonding

 

[Guest123]

300 a breaker i think, 3 phase supply and 400a across all 3 phases

You could have stated that from the beginning, save me going off on one!

400A per phase is totally different to 400A TP.

 

[matt12321]

sorry lenny.

so any ideas after all the info on the size and if i can run one single or 2 in parallel.

 

[topquark]

Well 2 x 50mm would give you a VD of around 5.75V .... you still haven't told us what's running on it though!. To achieve that VD with one cable you'd be up at 120mm (assuming I have my thinking head on).

 

[matt12321]

i dont know what it will be running, he didnt say. what size earth will 120 mm need

 

[topquark]

i dont know what it will be running, he didnt say. what size earth will 120 mm need

Then you need to ask him. Inrush current etc may need to be taken into account (unless he's already done that within the "spec" you've been given). As for the earthing requirements, what do the regulations tell you with regards to sizing?