Hi All
have a question on cable sizing as I'm calculating it at 16mm SWA I have 2 circuits that need to be replaced with new cables they are exist 10mm 2 core and 1000 metres total and first point is 350m the design current is 2.5 amps and is feeding some 12volt transformer, just after some feed back as to weather I can derate the cable some how
thanks in advance for any feed back
The usual fix is to move the DNO transformer nearer 
.
But failing that the next trick is to up the voltage - so you may find loads between 2 phases on a 400V supply (or even 690 in some large factories), rather than one phase and N to give 230V as you may expect on a shorter run. This is a standard wheeze for football ground lights for example. Of course if your 12V transformers are already wound for 230, this is not an option either.
If you know the load characteristics will be OK with it, then you can take more voltage drop than the regs appendix suggests, but not so much that a dead short at the end will not promplty fire the ADS - this tends to give an upper limit of 10% or so before special measures are needed to ensure safe fault handling.
Mike.
The usual fix is to move the DNO transformer nearer .
But failing that the next trick is to up the voltage - so you may find loads between 2 phases on a 400V supply (or even 690 in some large factories), rather than one phase and N to give 230V as you may expect on a shorter run. This is a standard wheeze for football ground lights for example. Of course if your 12V transformers are already wound for 230, this is not an option either.
If you know the load characteristics will be OK with it, then you can take more voltage drop than the regs appendix suggests, but not so much that a dead short at the end will not promplty fire the ADS - this tends to give an upper limit of 10% or so before special measures are needed to ensure safe fault handling.
Mike.
