Im working in easypower, attempting to model a sylvania SEH 3 c 125 breaker, it doesnt exist in the current library from what ive found and have tried contacting bentley support and they told me they've attempted to contact the current owner of that company but havent been able to get a TCC curve for that breaker. I've decided to use the generic breaker but am unsure if there was any rules of thumb when it comes to using generic breakers like this? this is the first time ive encountered not having a breaker in the library

thanks

Google says that is the same as a Challenger SEH3C125 breaker. I don't have either one in my SKM library. You might reach back out to Bentley and see if they have the Challenger breaker in their library.

I was able to get SKM's Sylvania SEH breaker TCC file. Interestingly, it has 120A and 130A breaker curves, which are not standard sizes, but no 125A curve. Not sure what is up with that. I tried to compare the 130A breaker curve to about 15 or 20 or so breaker curves from other manufacturers to see if there were any close enough to use as a substitute but had no luck there. At least not any the I would use confidently.

In any case, is your 125A breaker a main breaker or a feeder breaker? If it is a main breaker, I would calculate incident energy at the line side of the breaker and not think anymore about it.

If it is a feeder breaker, you really need to try harder to get the curve or you could just time it out with the 2 second rule OR use the upstream device as the protective device for whatever the downstream bus it. Neither of the latter is ideal but considering the age of the breaker, it may be actually be more appropriate if there is any concern that the breaker hasn't been maintain and may not work like it's supposed to anyway.