Partial & Total Discrimination Between 2 Circuit Breakers

I think it's the other way around; the smaller downstream CB should trip at 2KA less fault current (for the same amount of time) than the upstream CB; thereby powering down a smaller part of the total system.

You may get some knowledge from an earlier thread

http://cr4.globalspec.com/thread/71318

i am surprised by your statement that discrimination is total in ABB (are you referring to Tmax ?) while it is 2kA in Schneider (NSX?). i think even in ABB, discrimination is partial only.

MCCBs are usually current-limiting. They do not have I_cw rating. If you have a fault of 50kA on the system, it is quite likely that both MCCBs will trip. Or maybe the upstream or the downstream one. If you MUST have total discrimination up to the system maximum fault level, you have to use an ACB with an I_cw rating as the incomer.

You may get some knowledge from an earlier thread

http://cr4.globalspec.com/thread/71318

thank you i did gain some.

i am surprised by your statement that discrimination is total in ABB (are you referring to Tmax ?) while it is 2kA in Schneider (NSX?). i think even in ABB, discrimination is partial only.

one of my friends works in ABB in LV switchgear division. he told me that there was total discrimination.but now i did some research and it turns out he was wrong,i was wrong. there is no discrimination between the 2 breakers. sorry

If you have a fault of 50kA on the system, it is quite likely that both MCCBs will trip. Or maybe the upstream or the downstream one.

you are giving 3 answers. The use of words "quite likely" & "maybe" is very fragile, especially when designing . sorry , can u be sure which is the right option. i dont wanna take any risk.

what about my original question of 2KA discrimination?

If you MUST have total discrimination up to the system maximum fault level, you have to use an ACB with an I_cw rating as the incomer.

Using ACB for 160A will increase the cost, panel size etc. and ACB range starts from 600A in schneider and lowest setting in that breaker is 250A . so ACB cannot be used.