Selective coordination charts (from ABB)

[lielec11]

I have a chart from ABB indicating that an upstream/downstream breaker combination is selectively coordinated up to 14kA. However, when I put these curves into SKM, they actually overlap in the INST/short-time region. In the image below, I'm talking about the blue/purple curves. The tables tell me they should be coordinated, however, the curves do not. We submitted our report indicating they don't coordinate based on the curves, however, the EOR has come back saying otherwise.

I remember watching a presentation by Thomas Domitrovitch (from Eaton) stating that the tables are actually to determine selectivity BEFORE 0.01s and that the TCC curves also need to be fully coordinated as well. Any input on which train of thought to lean on here?



Thanks

 

[dkidd]

Maybe this will help:

::: SKM Power*Tools ::: ELECTRICAL ENGINEERING SOFTWARE Home Page

 

[don_resqcapt19]

I believe Tom D mentioned using the tables that all of the breaker manufacturers have to determine the coordination below the 0.01 time.
Using just the curve, I see this breakers as coordinated above the 0.01 second time as long as the available fault current does not exceed 15kA.

 

[mayanees]

Selective Coordination Realistic? | Mike Holt's Forum
Hey
We just did a thread on this.
The TCCs won't necessarily show selectivity, so you need to use the manufacturer-provided series charts for selectivity and current ratings.

 

[lielec11]

Maybe this will help:

::: SKM Power*Tools ::: ELECTRICAL ENGINEERING SOFTWARE Home Page

We currently do not pay for this feature in SKM so I cannot go through it on our project, but thanks for the reference.

I believe Tom D mentioned using the tables that all of the breaker manufacturers have to determine the coordination below the 0.01 time.
Using just the curve, I see this breakers as coordinated above the 0.01 second time as long as the available fault current does not exceed 15kA.

Thanks, Don. I tend to agree just always like to get another opinion in certain situations.

Thanks, John for the link to the other thread, I'll go through that as well!