Selectivity between circuit breakers?

[bevvet]

Hello. I am reading up on circuit breakers. I need to know how to get good selectivity between circuit breakers, for overload and shortcircuit protection. Selectivity just means that only the circuit breaker closest to the fault will trip.

Often, you can use charts to figure this out if it is good selectivity if the circuit breakers are from the same brand. But in the case that you use different type circuit breakers, how do you check the selecitivty?

[S-W]

Hello @bevvet , thank you for your message, we'll come back to you with a reply soon.

[Gregoire_Brun · Accepted solution]

hello @bevvet 

please have a look on this web page 

Electrical Calculation Tool (se.com)

You can use this Tools for a quick Protection device Selection, Selectivity Checking and Cable Calculation....

[NeiB · Accepted solution]

Hi @bevvet ,

Wish you are well.

According to IEC requirements, the Selectivity and Cascading tables must be tested on a third party laboratory or calculated with an modelling software IEC approved. I guess this is why there is no brand mixing when performing this test. There are costs involved and the success of this type of tests are not guaranteed.

Furthermore every product has its own type of technology that enhances the Selectivity/Cascading as for example our REFLEX trip from NSX and it would be compatible with the range of families/products with the same manufacturer.

I believe that softwares like ETAP is able to simulate Coordination (Selectivity/Cascading) on circuits with different brands as you can see on the video below for instance:

As far as I know, this software uses the curves and libraries it has installed from each manufacturer:

https://etap.com/product/star-protective-device-coordination-software 

One important point is that it is not possible to mix standards like IEC and NEC/UL for example.

Best Regards,

Neide