Distribution Boards

[SAkieran]

is there any good website or articles to help a novice when compiling dbs for UPS, DC supply etc. it doesn't look too difficult but i am not sure about fault ratings and what to look out for when designing these, i have most of the loads, i also need to compile a rfq but that shouldn't be too difficult

 

[AusLee]

SAkieran,

IEC 60439.1 is applicable to low voltage switchboards at DC level not exceeding 1500V.

The only difference i see is that the arc in DC is much stronger than in AC because the voltage does not vary, stays constant at the high value. The DC switchboard should cost at least double what it would

Apart from the specification that all breakers and switches have DC amps rating and appropriate voltage, please take a look at this extract from the IEC standard section 7.5 "Short-Circuit Protection"

"NOTE For the time being, this subclause applies primarily to a.c. equipment. Requirements concerning d.c
equipment are under consideration."

It means you are on your own. It is worth the while if you ask the supplier if they have done type tests on the switchboard using DC supply. Please share your findings in this regard. It it was up to me, i would deal with it this way:

1. Find out the short-circuit contribution of the UPS.
2. Find out the short circuit from the power supply at the by-pass switch.
3. Add 1+2 and multiply by 1.25 which seems to be the universal safety factor and require the switchboard to have a fault rating equal to this value for 1 second.