Voltage Drop?

[Dan-R]

Hi this is my first time on this forum so take it easy please but I'm after a little bit of advice... I wonder if someone can help me calculate the voltage drop of an install that is in the process... I will give you as much info as possible, any help would be greatly appreciated...

.400a main intake head has been installed with a 400a isolator (3 phase 400v)
.Job is the install a sub main cable to feed an LV panel (400 supply)
.Sub main cable is SWA PVC 4core wired outside across a roof on perforated cable tray with a separate earth
.Cable run is 50m

I am trying to work out what size cable will be required and can't get to grips with the formula's, again any help would be appreciated.

Thanks Dan

 

[telectrix]

assume that your max. allowable VD is 5%,

mV/A/m = (VD x 1000)/(L x A) . so once you have your mV figure, look up what cable size has that value.

 

[Simonslimline]

Surely you would of learned this in college, your profile does state you are an electrician!

 

[Spoon]

Hi Dan. Welcome to the forum.
Am I understanding you post correctly? You want to feed a LV Panel that has a cable run of 50 meters and is protected by a 400A breaker?

400A cable is going to be big. It may be better running two cables in parallel.