Cable sizing question

[Sparky-Tom]

As part of my HNC project I have to calculate the cable size for a SWA cable. It's 4 core (3ph and neutral) running in a trench with a 'roof' of concrete (theres a big air gap around the cable) with no other cables in the trench. The run is roughly 20m long.

I've looked in the 16th and 17th edition regs books, and I have made multiple searches on Google. Could anybody point me in the right direction?

Much appreciated

Tom

 

[Electricalserv]

As part of my HNC project I have to calculate the cable size for a SWA cable. It's 4 core (3ph and neutral) running in a trench with a 'roof' of concrete (theres a big air gap around the cable) with no other cables in the trench. The run is roughly 20m long.

I've looked in the 16th and 17th edition regs books, and I have made multiple searches on Google. Could anybody point me in the right direction?

Much appreciated

Tom

Need more info...what load is it supplying?

 

[RWJ]

As part of my HNC project I have to calculate the cable size for a SWA cable. It's 4 core (3ph and neutral) running in a trench with a 'roof' of concrete (theres a big air gap around the cable) with no other cables in the trench. The run is roughly 20m long.

I've looked in the 16th and 17th edition regs books, and I have made multiple searches on Google. Could anybody point me in the right direction?

Much appreciated

Tom

I don't intend sounding snobby or to offend but you really should know this stuff if you are doing an HNC??

 

[Guest123]

You would first need to ascertain the (Ib) of the circuit then select an appropriate protective device rating (In),apply any installation factors to it and select a cable with a tabulated rating (It) greater than (In) with any factors applied.

After that consider VD, shock protection (EFLI) & thermal constraints (adiabatic equation).

 

[Engineer54]

I think he is only asking for the installation method number, not how to calculate the cable size. I too often have trouble finding the numbers of different method numbers as classified in the BRB!! ....I always seem to find the one i'm after, is never a straight look up operation. ...lol!!!

 

[Sparky-Tom]

I don't intend sounding snobby or to offend but you really should know this stuff if you are doing an HNC??

You're right I should know this stuff if I'm doing an HNC, but my HNC is more electronics based. This question is only for my project management module, not for a technical module. The project is to replace a transformer at a factory, the transformer is 11Kv to 3 phase 415v.

You would first need to ascertain the (Ib) of the circuit then select an appropriate protective device rating (In),apply any installation factors to it and select a cable with a tabulated rating (It) greater than (In) with any factors applied.

After that consider VD, shock protection (EFLI) & thermal constraints (adiabatic equation).

Lenny, could you give general values for these? The cable is feeding a busbar chamber in a workshop/plantroom with a load of up to 2000A per phase

Thanks for the replies guys!