Selective Coordination to 0.01

[lielec11]

It sounds like talking about having the instantaneous region stop at the available fault current, like Charlie was talking about.

If you are using SKM software, I believe there is an option to terminate the breaker curve at the available fault current.

Open a TCC curve, select a breaker curve, right click and select "Selected Device Settings", click the "SC Rag" tab. There you can show the Short circuit current on the plot, and choose how to display the curve for the breaker.

I just figured this out, for some reason it wasn't applying properly earlier in the day. Things appear fine now.

thanks for all your help.

 

[jim dungar]

I misunderstood your comment.

Instantaneous override is effectively just setting the instantaneous to its maximum value, but it still existing in the protection curve. I had power breakers in mind, where if you turn it off, it is really off.

Using a 'maximum' setting still creates the traditional 'hockey stick' curve, using the 'off' setting creates some room (several cycles) under the Instantaneous portion. At the overide, or 'self protection' point the curve returns to normal.

Power breakers (ANSI style) are an entirely different animal. The phrase I used was PowerPact, which Square D's present generation of molded case breakers.

 

[don_resqcapt19]

Both code changes classes that I attended said that the new definition requires coordination for all possible currents and times, that is no matter what the current is, the closest breaker to the fault has to open without the upstream breakers opening. The classes made a very strong distinction between the Article 100 definition and the Article 517 definition.
From a panel statement in the ROC.

Panel Statement: The ?Accept in Principle? wording accepted by CMP 10 during ROP meeting, clearly does not contain a requirement for when or where selective coordination is required. It does however clarify the definition of ?Coordination, Selective?. This clarification is necessary because, as described in the original substantiation;
The NEC needs to remain the quintessential document for the electrical system safety issue, and while the existing definition has served us well for many years, it is now necessary to clarify the definition, not change the meaning. The proposed changes add the specific clarity that is needed.
The wording accepted by CMP 10 is necessary to distinguish between the word ?Coordination? and the phrase ?Selective Coordination?. The word ?Coordination? is often used to describe the isolation of downstream overcurrent conditions over limited ranges of time and currents, but selective coordination is used to describe the isolation of downstream overcurrent conditions over the complete range of available overcurrents and the times associated with those overcurrents.
The 0.1 second limit for isolation of downstream overcurrent conditions, referred to in the substantiation of the submitter in the reference to NFPA 99, actually describes ?Coordination? down to 0.1 seconds, not ?Selective Coordination? down to 0.1 seconds.
?Total Coordination? is synonymous with the phrase ?Selective Coordination?. The words ?coordinate? or ?coordination? alone are simply not sufficiently specific enough to describe the concept as utilized by CMPs 12, 13, and 20.