Circuit Breaker

Short circuit or interrupting capacity relates to the construction of the particular circuit breaker in question and is commonly stated in the part description or in the datasheet.

For Special interrupting capacity values or durations not mentioned, these can be calculated either from application datasheets provided by the circuit breaker manufacturer or from standards relating to specific circuit breaker type (for example IEC 60898, UL1077, etc), although this in my experience is rarely needed as you select the correctly rated circuit breaker for the application.

Now, if you want to calculate the actual short circuit current that the supply can provide that is a different story. Generally you look at the application and estimate or refer to local electrical standards which tell you (for example down here residential alternating current circuits are commonly protected by circuit breakers rated at 6kA), otherwise you have to calculate or use software but you need to know circuit impedances, transformer characteristics, etc. Not a simple job.

What are you trying to do?

Jenyam,

I believe that it is time for you to do your own homework, or work.

All your questions could have been (can be) answered by simple Google searches.

Breaking capacity - Wikipedia, the free encyclopedia

More importantly, all your questions can be answered by purchasing, or at least reading, the electrical codes now in force worldwide.

There's a good boy. Now, run along and do some work. Make us proud.

I think we have either a translation to English problem here or a misunderstanding of the topic of current interruption in a circuit breaker.

Unless one is designing circuit breakers themselves one does not compute the maximum current interruption capability of a circuit breaker. One just uses a manufacturer's data in one's design. Even if one is designing a circuit breaker, this is an attribute that is measured in destructive testing. (There are non-destructive tests that one can perform that imply this current but destructive testing should eventually be performed to verify.)

To identify the maximum current available in a short circuit condition is similar to an arc flash analysis. This can be a very tedious analysis in an industrial environment that requires knowing the power distribution transformers used to feed a breaker panel and all of the major motors that can be connected on both sides of the breaker panel and the wire gauge and lengths used to connect them all. In most residential and commercial applications this is just information your utility provides.

This link:

http://www.msha.gov/TECHSUPP/ACC/shortcircuit/shortcuit.htm

Brings you to a program provided by the Mine Safety and Health division of the U.S. Department of Labor, were the intent is to prevent cables from "glowing" rather than tripping a circuit breaker. Perhaps it may be of some use to you.

My friend in the UK is an electrician and has just been awarded a knighthood.
He's now known as Sir Kit Breaker.

Groan

Calculating the prospective short-circuit current is a protocol, given fully in British Standard 7671, again.