Short Circuit

Dear Sir, Could you please guide me about the purpose of Short circuit current calculations? Normally in UAE, we select the breaker in such a way that: * Entrance level breaker has 65KA short circuit rating * Branch breakers are 35KA and * Sub-branch circuits breakers are 25KA * Last Breaker near the load center we use 6KA short circuit capacity circuit breaker.. But we are not using any long calculations for short circuit analysis or any thing like this and things are going well but i studied in my engineering program but could not get any chance to implement it. please guide me where is an actual use of this short circuit analysis?

Let us just say it is used alot in ARC flash analysis.

what is a purpose of arch flash analysis????

Ususally you make this SCC calculation before selecting any devices. You calculate for the lowest SCC to select the right CBs so they still switch off in case and you calculate for the highest SCC to select devices to withstand this load. Beside that if it comes to an inspection (maybe you dont have them in UAE, but in Europe, US, CAN and other parts of the world they usually have), one of the first questions of the inspector will be the availability of the SCC-calculation according to the applying standards in that country. So there are reasons to have this calculations...

Also think about if it comes to a bigger hazard... You will need answers at the court. Maybe they ask "why did you use this or that device"... Then you should be able to present your DOCUMENTED calculation and tell them that you did your tasks correctly... Also insurance could be a factor. They also could ask for this calculations. But as I wrote before, I dont know the situation in UAE, that at least is true in other countries.

Its is my humble request to you if you can guide me how to make short circuit calculation practically ???? what type of information should we required to start the short circuit calculation??

Hi ASAD ALI,

Try these links.
"
http://www.schneider-electric.co.in/documents...now-how/low-voltage-minus-1kv/ect158.pdf(SCC)":http://www.schneider-electric.co.in/documents/technical-publications/en/shared/electrical-engineering/electrical-know-how/low-voltage-minus-1kv/ect158.pdf


"Your text to link here...(scc)":http://ecmweb.com/basics/basic-short-circuit-current-calculation

Peters Linkhas an "SCC" to much... here is the Link again without the SCC (as well as other links to the same area):

http://www.schneider-electric.co.in/documents...cal-know-how/low-voltage-minus-1kv/ect158.pdf

http://www.geindustrial.com/publibrary/checkout/GET-3550F?TNR=White Papers|GET-3550F|generic

http://www.cooperindustries.com/content/dam/public/bussmann/Electrical/Resources/Solution Center/technical_library/BUS_Ele_Tech_Lib_Short_Circuit_Current_Calculations.pdf

Besides the manual calculation you can also use programs to do the calculation for you (but of course you should know how the calculation works so you can proof the output of the computations...)
One of this programs is called "Neplan" (now belonging to ABB):

http://www.neplan.ch/html/e/e_home.htm

Another is called Palladin DesignBase:

http://www.poweranalytics.com/designbase/main.php

Another possibility is to outsource this calculation to a thirdparty company specialized for this tasks...

For some reason the links are shown broken... I give the links again as strings:

"http://www.cooperindustries.com/content/dam/public/bussmann/Electrical/Resources/Solution Center/technical_library/BUS_Ele_Tech_Lib_Short_Circuit_Current_Calculations.pdf"


"http://www.geindustrial.com/publibrary/checkout/GET-3550F?TNR=White Papers|GET-3550F|generic"