It is currently Mon Aug 10, 2020 8:02 am



Post new topic Reply to topic Go to page 1, 2  Next

Based on IEEE C7.05 section 5.6, do you add an extra half or full cycle to your time?
Yes: I use 3.5 cycles for a 3 cycle breaker and 6 cycles for a 5 cycle breaker before adding relay t
No: Rated breaker time plus relay time is sufficient.
Depends on situation.
Other
You may select 1 option

View results
Author Message
ekstra   ara
 Post subject: interrupting time poll
PostPosted: Mon Apr 05, 2010 9:37 am 
Arc Level

Joined: Tue Jan 13, 2009 5:00 pm
Posts: 532
No response to the first thread. Perhaps a poll will collect more?

Based on IEEE C37.04 section 5.6, do you add an extra half or full cycle to to your breaker rating when figuring IE?


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Mon Apr 05, 2010 12:10 pm 
Arc Level

Joined: Wed Jun 04, 2008 9:17 am
Posts: 428
Location: Spartanburg, South Carolina
Maybe if you quoted the referenced section and the title of the standard. I can't find a C7.05 in browsing through IEEE Xplore. I also can't find a C37.05.


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Mon Apr 05, 2010 12:46 pm 
Plasma Level

Joined: Mon Jun 02, 2008 11:58 am
Posts: 1103
Location: Charlotte, NC
I said other because we now try to base our studies of first trip data, not a table that says when it "should" trip.


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Mon Apr 05, 2010 1:04 pm 
Arc Level

Joined: Tue Jan 13, 2009 5:00 pm
Posts: 532
Sorry, corrected in the body; but I see no way to correct the question.

"5.6 Rated interrupting time
The rated interrupting time of a circuit breaker is the maximum permissible interval between the energizing
of the trip circuit at rated control voltage and rated operating pressure for mechanical operation, and the
interruption of the current in the main circuit in all poles. The interrupting time for a close-open operation
shall not exceed the rated interrupting time by more than 1 cycle of rated power frequency for circuit breakers
with interrupting times of 5 cycles or more, and 1/2 cycle for circuit breakers with interrupting times of
3 cycles or less. (Cycles are based on corresponding rated power frequency.)"

Please note that the adder is for a CO operation. This is a close into fault situation.


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Mon Apr 05, 2010 1:08 pm 
Arc Level

Joined: Tue Jan 13, 2009 5:00 pm
Posts: 532
Zog,

Please explain. Where do you get "first trip data?"

Breaker rated interrupting time is not used?

I never suggested using a table.


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Mon Apr 05, 2010 3:18 pm 
Plasma Level

Joined: Mon Jun 02, 2008 11:58 am
Posts: 1103
Location: Charlotte, NC
stevenal wrote:
Zog,

Please explain. Where do you get "first trip data?"

Breaker rated interrupting time is not used?

I never suggested using a table.


Table, software database, whatever, all the same, not real values. Not trying to pick on you though, most people are still doing it with published data. The future of accurate studies is first trip data. (Google it and you will see all the articles, gathering a lot of steam in the testing world).

(The following is reposted from a NETA world article by my co-worker, Don Genutis)

Typically, circuit breakers remain dormant for very long periods of time, but when called upon to interrupt a fault, they are expected to operate within finite times based upon their protective settings. These settings are derived by conducting coordination and arc-flash studies to optimize electrical system performance and enhance worker safety. Typically, the breaker’s lubrication conditioncchanges over time, due to a number of factors, and hardens to a point where the breaker’s first trip is inhibited. This first trip represents the breaker’s true operating time and often differs greatly from the values expected in the studies thus adversely affecting system performance and exposing the worker to higher levels of incident energy and making the studies invalid.

The only solution to validate the studies and to protect the worker is to frequently verify breaker timing under first trip conditions. Typical maintenance and testing occurs after the breaker has already been tripped once, and thus the critical first trip condition information is lost. Regular exercising of the breaker can help the first trip performance. Frequent maintenance will also help, but these activities do not ensure optimum first trip operation.

A new technology has evolved that efficiently determines breaker first trip performance thus enabling validation of the arc-flash study. This technology has the additional benefit of verifying overall breaker mechanical condition. A special transducer is magnetically coupled to the front of the breaker ,after the technician moves from the exposure zone, the breaker is operated. The
transducer sends valuable vibration signals that represent breaker first trip timing and mechanical condition to a handheld analyzer. This unique breaker vibration signature is compared to a database library of known signatures.

Post test analysis can include superimposing the test breaker signature upon good breaker signatures to quickly spot potential problems. Should the breaker fail the first trip test in the field, it is necessary to perform complete shop reconditioning or remanufacturing in order to return the breaker to a condition that will ensure proper operation and validate the arc-flash study. Frequent performance of the breaker vibration signature test ensures performance and exercises the breaker mechanism.

Here is a link to the full article, http://www.nooutageelectricaltesting.com/PDF/no-outage-safety.pdf


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Tue Apr 06, 2010 12:34 pm 
Arc Level

Joined: Tue Jan 13, 2009 5:00 pm
Posts: 532
Zog,

Seems to be a verification of the breaker mechanical operating time. Not sure how you get from there to the interrupting time. A "first interrupting time" test would require a source capable of supplying rated interrupting current to the breaker. I think I'll leave that to the manufacturers. And we seem to be considering only an open after a long time closed, just the opposite of my suggestion to use the CO extra half or full cycle.


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Tue Apr 06, 2010 12:47 pm 
Plasma Level

Joined: Mon Jun 02, 2008 11:58 am
Posts: 1103
Location: Charlotte, NC
stevenal wrote:
Zog,

Seems to be a verification of the breaker mechanical operating time. Not sure how you get from there to the interrupting time. A "first interrupting time" test would require a source capable of supplying rated interrupting current to the breaker. I think I'll leave that to the manufacturers. And we seem to be considering only an open after a long time closed, just the opposite of my suggestion to use the CO extra half or full cycle.


You can have the fastest relay in the world but if the breaker will not open in the assumed time it does you no good. We simulate they fault curent via secondary injection with the breaker still in the cell. Primary injection can only be done after the breakr is removed from the cell and is still done to verify the CT's are operating correctly after the first trip data is recorded.

First trip is the future of breaker testing and arc flash studies, stay tuned.


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Tue Apr 06, 2010 3:55 pm 
Arc Level

Joined: Tue Jan 13, 2009 5:00 pm
Posts: 532
Zog,

Secondary injection does not emulate the way primary fault current is cleared. You can have the fastest breaker mechanism in the world, and it will do you no good if the current continues to arc across the contacts for very long.

And primary injection test sets cannot provide sufficient current/voltage to emulate a real fault.

Clearing time = relay time + interrupting time.

Interrupting time = opening time + arcing time.

For an illustration see C37.010 Figure 2. I fear your method is neglecting the arcing time.


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Wed Apr 07, 2010 9:41 am 
Arc Level

Joined: Wed Jun 04, 2008 9:17 am
Posts: 428
Location: Spartanburg, South Carolina
If I understand the standard correctly, the extra time would only apply when closing into a fault. In this case, the actual arcing time at the fault location will be less than the CO time of the breaker. Before the breaker is closed, there is no voltage at the fault location and no arcing. To close into a fault would mean that the fault would either be bolted to start with (no gap) or have a very small gap that would arc over after energization. It could develop into an arc across the assumed gap distance, but only after some finite time.

I voted for using interrupting time plus relay time.


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Wed Apr 07, 2010 11:07 am 
Plasma Level

Joined: Mon Jun 02, 2008 11:58 am
Posts: 1103
Location: Charlotte, NC
stevenal wrote:
Zog,

Secondary injection does not emulate the way primary fault current is cleared. You can have the fastest breaker mechanism in the world, and it will do you no good if the current continues to arc across the contacts for very long.

And primary injection test sets cannot provide sufficient current/voltage to emulate a real fault.

Clearing time = relay time + interrupting time.

Interrupting time = opening time + arcing time.

For an illustration see C37.010 Figure 2. I fear your method is neglecting the arcing time.



Not at all, still factored in, but our method is finding the real opening time, not the assumed opening time.


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Wed Apr 07, 2010 12:42 pm 
Arc Level

Joined: Tue Jan 13, 2009 5:00 pm
Posts: 532
Then the arcing time is the remaining assumption. How do address this value?


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Wed Apr 07, 2010 3:02 pm 
Plasma Level

Joined: Mon Jun 02, 2008 11:58 am
Posts: 1103
Location: Charlotte, NC
stevenal wrote:
Then the arcing time is the remaining assumption. How do address this value?


Opening time is dependant on the mechanical condition of the breaker and will change over time, arcing current is not and depends on the calculatable properties of the system.


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Wed Apr 07, 2010 4:38 pm 
Arc Level

Joined: Tue Jan 13, 2009 5:00 pm
Posts: 532
Zog,
We seem to have a failure to communicate.

I asked about arcing time, not current. This is the time from initial pole opening until the fault is cleared. (This arc is that which occurs inside the breaker interruption chamber, not the arc flash event at the fault location) Your breaker timing test does not include this piece. How do you account for it? By the scaling of C37.010 Fig.2, the arcing time makes up more than half the interruption time.
Image


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Wed Apr 07, 2010 5:08 pm 
Plasma Level

Joined: Mon Jun 02, 2008 11:58 am
Posts: 1103
Location: Charlotte, NC
stevenal wrote:
Zog,
We seem to have a failure to communicate.

I asked about arcing time, not current. This is the time from initial pole opening until the fault is cleared. (This arc is that which occurs inside the breaker interruption chamber, not the arc flash event at the fault location) Your breaker timing test does not include this piece. How do you account for it? By the scaling of C37.010 Fig.2, the arcing time makes up more than half the interruption time.
Image


But the opening time is the variable here. I think we are not communicating well, but we are thread jacking. ABB and GE are both using similar technology and there are many white papers on first trip technology available by people more involved in it than I am .


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Wed Apr 07, 2010 6:03 pm 
Sparks Level

Joined: Sun Dec 23, 2007 1:44 pm
Posts: 348
Location: Charlotte, NC
I for one do not think you are thread jacking.....why not go forward and see where it leads?


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Thu Apr 08, 2010 6:39 am 
Sparks Level

Joined: Sun Dec 23, 2007 1:44 pm
Posts: 348
Location: Charlotte, NC
I also voted for relay time + rated interrupting time. This is based on the interrupting time being the total contact parting plus arcing time.

Seems to me that the CO requirement is a specific equipment design test.

If we have to assume the breaker will not operate as advertised, then shouldn't we also assume that the relay won't either....and, if so, where does it end?

And I have to "ponder" what has happened to the downstream fault once we start the arcing in the breaker?


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Thu Apr 08, 2010 8:10 am 
Arc Level

Joined: Tue Jan 13, 2009 5:00 pm
Posts: 532
Zog,

I also think this is a worthwhile discussion that should continue. If you consider arcing time to be constant, what constant do you use and where do you get it from?

I must also question that opening time is the only variable. If first trip measurement finds a slow opening time due to a slow mechanism, the arcing time will also likely be extended as it will take longer to get from contact parting to the point where the arc is extinguished.


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Thu Apr 08, 2010 9:33 am 
Plasma Level

Joined: Mon Jun 02, 2008 11:58 am
Posts: 1103
Location: Charlotte, NC
stevenal wrote:
Zog,

I also think this is a worthwhile discussion that should continue. If you consider arcing time to be constant, what constant do you use and where do you get it from?

I must also question that opening time is the only variable. If first trip measurement finds a slow opening time due to a slow mechanism, the arcing time will also likely be extended as it will take longer to get from contact parting to the point where the arc is extinguished.



Good point about the arcing time, I will have to ask our first trip guru about how they handle that one.


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Sun Apr 11, 2010 7:02 pm 
Plasma Level
User avatar

Joined: Mon Sep 17, 2007 5:00 pm
Posts: 1501
Location: Scottsdale, Arizona
I voted breaker and relay time is sufficient since that is what I have done in the past but I am not convinced it is the correct thing to do for arc flash studies. Problem is, I'm not sure what a good answer would be. There is some good info in this thread that I am going to have to ponder.

This issue was brought up at an IEEE 1584 meeting some time ago,the actual issue was whether to require adding some additional factor to account for age and maintenance for safety. It was only a discussion on the floor but it was discussed and debated but eventually it was decided to just base the clearing time on time current curves / breaker times / induction disc overtravel etc. and if others want to add some additional factor, it is up to them.

As so many are aware, age, condition and maintenance can have a very large impact. Incident energy is directly proportional to duration so a "hiccup" in a device's operation can create a significant increase in the Ei.

Good survey question!

_________________
Jim Phillips, P.E.
Brainfiller.com


Top
 Profile Send private message  
Reply with quote  
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 30 posts ]  Go to page 1, 2  Next

All times are UTC - 7 hours


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Jump to:  
© 2019 Arcflash Forum / Brainfiller, Inc. | P.O. Box 12024 | Scottsdale, AZ 85267 USA | 800-874-8883