Not sure where you got the arcing time from. I'll throw one more out. It is either saying that the relay is tripping in 20 ms and the breaker takes 40 ms to open (20+40=60 ms), or that the tested total opening time is 20 ms, or that opening time is specified as 40 ms but it was tested and operated a little faster, or that the relay information is simply extra data. So the total clearing time is either 20, 40, or 60 ms, but definitely not 75 ms. As a conservative approach I'd take 60 ms if I didn't have follow up data from the manufacturer stating otherwise.

I have seen arcing time associated with fuses. Clearing time = melting time + arcing time.

This breaker is built in accordance with IEC 60947-2 - I am not intimately familiar with the IEC standards so I'll have to see if I have this one at work. If I have a copy of the standard I'll reply back here, or you could obtain a copy of the standard yourself and read about what the various breaker ratings mean. The answer to your question will be available in the standard.

None of the following applies to your particular question since your breaker is not built to these standards, but this is some relevant technical background:

Breakers over 1000V built to the ANSI C37 suite of standards have a rated interrupting time and a rated contact parting time. The rated interrupting time is the figure that is commonly known, typically 3 cycles, 5 cycles, or 8 cycles. This is the time that is added to relay time and auxiliary device time when calculating the clearing time for arc flash purposes.

The interrupting time consists of the contact parting time plus the arcing time. The contact parting time is typically published in the circuit breaker manual and is used for testing the speed of the operating mechanism. Numerous simple test sets can pass a small current through each pole of the circuit breaker, issue a trip command, and measure the time period until the current stops flowing - this is the contact parting time. A time travel analyzer is a more sophisticated test set that measures the position of the operating mechanism as well while performing the above test. Some metal clad switchgear breakers have provisions for attaching the required position sensor, and most SF6 breakers have these provisions. Since the arcing time cannot be measured directly without using rated voltage and rated current (which would require a high current test cell), the contact parting time is measured instead as a proxy for checking the interrupting time.

I did not mention that I had contacted the L&T guys - the breaker manufacturers, for the same issue.

It all began with ETAP. The software was not considering the breaker opening time with a release. I mean it was only reading out 'time' from the TCC of release curve. I had been skeptical of its approach. I contacted an ETAP expert and confirmed its (ETAP's) behavior. However the breaker opening time is considered if an external relay is considered.

The approach of ETAP (considering only the release curve for breaker opening time - no consideration for opening time of breaker) may be true in case of Thermal Magnetic breakers, but in the case of microprocessor/solid state, I am not sure (please comment on the same).

Then came the L&T breaker where I had to build the TCC. Now that the software (ETAP) doesn't consider the breaker opening time in case of a release, I had to input the TCC with the breaker opening time included. I had this doubt whether the breaker clears the fault in 20 ms or 40 ms or 60 ms (problem above).

I dropped in an email to the L&T switchgear training center guys. They gave me the above value for arcing time (15 ms). I was unsure about the net opening time of the breaker. I remember reading that that opening time of the breaker includes the arcing time as well (arc extinction and related concepts). When I asked how (to the L&T guys), they gave me the following definitions:
[font=Tahoma][color=#141414][/color][/font]
[font=Times New Roman]Opening Time: It is the interval of time between the specified instant of initiation of the opening operation & the instant when the arcing contacts have separated in all poles. The instant of initiation of the opening operation means the instant of the application of the opening command, e.g. energizing the release etc. In case of a directly operated circuit breaker, the instant of initiation of the opening time is the instant of initiation of a current large enough to cause the circuit breaker to operate. In the case of a circuit breaker operated by any form of auxiliary power, the instant of initiation of the opening time is the instant of application of the auxiliary power to the opening release. For circuit breakers opening time is commonly referred to as tripping time, although, strictly speaking, tripping time applies to the time between the instant of initiation of the opening time and the instant when the opening command becomes irreversible.[/font]
[font=Times New Roman][/font]
[font=Times New Roman]Arcing Time: It is the interval of time between the instant of initiation of the arc in a pole or a fuse & the instant of final arc extinction in that pole or that fuse. In a multiple-pole switching device, it will be the interval of time between the instant of the first initiation of an arc & the instant of final arc extinction in all poles.[/font]
I have the above info and now I am unsure of what to take the net opening time for this or for that matter any breaker..
Regards
Girish

Based on this, I would say that Clearing Time = Opening Time (40mS) + Arcing Time (15mS) = 45mS

Why should we ignore relay/release time (20 ms)? Because the definition of opening time indicates the receiving of opening command and what logically follows is that the time of relay/release should be considered. (Comments here please!)
What about other breakers? Does the arcing time come around 15 ms for a vast majority?
It seems to me that the software programs are not considering this time (arcing time) at all, at least ETAP doesn't. How about SKM and others in this league?

Because in the definition you posted for opening time, it states "...The instant of initiation of the opening operation means the instant of the application of the opening command, e.g. energizing the release, etc..."

This leads me to believe the opening time includes the relay/release time is included in the opening (or trip) time. I could be misunderstanding the definition, though.

The 15mS arcing time came from the circuit breaker manufacturer, but I am not certain you can even say that the time is typical for all instances of even that particular circuit breaker. The arcing time is going to be influenced by the L/R ratio of the wires connected to it. (Not to be confused with the X/R ratio - L/R is the time constant of the Inductance-to-Resistance ratio similar to RC time constants)

Upon reading the definition of opening time I have understood that it (opening time) is the time between the following events 1. energizing the release and 2. the contacts have parted..
So the opening time may not include the release time. It should start after the release has acted.





Sorry, but there is no mention of arcing time in the datasheet. I have not seen such a value in any datasheet! Please point me to any such datasheet (from any manufacturer) which specifies the arcing time value. However, I have seen it (Arcing time value) in a technical paper (white paper) from Siemens and not in a datasheet (catalogue).

Shall I contribute my opinion on L/R and X/R. I believe L/R is similar to X/R in a way that X/R=W * L/R ; where W = 2 * pi * f. However the units are different, thanks to W. (comments please)

Reading the definition of opening time reveals that it (opening time) is the time between the following events 1. energizing the release and 2. the contacts have parted..
So the opening time may not include the release time. It starts after the release has acted.




There is no mention of arcing time in the datasheet. And for that matter I have not seen such a value in any datasheet! Please point me to any such datasheet (from any manufacturer) which specifies the arcing time value. However, I have seen it (Arcing time value) in a technical paper (white paper) from Siemens and not in a datasheet (catalogue).

Shall I contribute my opinion on L/R and X/R. I believe L/R is similar to X/R in a way that X/R=W * L/R ; where W = 2 * pi * f. However the units are different, thanks to W.

Reading the definition of opening time reveals that it (opening time) is the time between the following events 1. energizing the release and 2. the contacts have parted..
So the opening time may not include the release time. It starts after the release has acted.




There is no mention of arcing time in the datasheet. And for that matter I have not seen such a value in any datasheet! Please point me to any such datasheet (from any manufacturer) which specifies the arcing time value. However, I have seen it (Arcing time value) in a technical paper (white paper) from Siemens and not in a datasheet (catalogue).

Shall I contribute my opinion on L/R and X/R. I believe L/R is similar to X/R in a way that X/R=W * L/R ; where W = 2 * pi * f. However the units are different, thanks to W.

Reading the definition of opening time reveals that it (opening time) is the time between the following events 1. energizing the release and 2. the contacts have parted..
So the opening time may not include the release time. It starts after the release has acted.




There is no mention of arcing time in the datasheet. And for that matter I have not seen such a value in any datasheet! Please point me to any such datasheet (from any manufacturer) which specifies the arcing time value. However, I have seen it (Arcing time value) in a technical paper (white paper) from Siemens and not in a datasheet (catalogue).

Shall I contribute my opinion on L/R and X/R. I believe L/R is similar to X/R in a way that X/R=W * L/R ; where W = 2 * pi * f. However the units are different, thanks to W.

Reading the definition of opening time reveals that it (opening time) is the time between the following events 1. energizing the release and 2. the contacts have parted..
So the opening time may not include the release time. It starts after the release has acted.




There is no mention of arcing time in the datasheet. And for that matter I have not seen such a value in any datasheet! Please point me to any such datasheet (from any manufacturer) which specifies the arcing time value. However, I have seen it (Arcing time value) in a technical paper (white paper) from Siemens and not in a datasheet (catalogue).

Shall I contribute my opinion on L/R and X/R. I believe L/R is similar to X/R in a way that X/R=W * L/R ; where W = 2 * pi * f. However the units are different, thanks to W.

Reading the definition of opening time reveals that it (opening time) is the time between the following events 1. energizing the release and 2. the contacts have parted..
So the opening time may not include the release time. It starts after the release has acted.




There is no mention of arcing time in the datasheet. And for that matter I have not seen such a value in any datasheet! Please point me to any such datasheet (from any manufacturer) which specifies the arcing time value. However, I have seen it (Arcing time value) in a technical paper (white paper) from Siemens and not in a datasheet (catalogue).

Shall I contribute my opinion on L/R and X/R. I believe L/R is similar to X/R in a way that X/R=W * L/R ; where W = 2 * pi * f. However the units are different, thanks to W.

I would have to see a timing chart. For me the expression "between energizing the release and the contacts have parted" includes the release time. Again, I may be misunderstanding the definition

You are the one that said it was 15mS. I thought you got it from the breaker manufacturer, but I see that you said, "L & T Switchgear Training Center guys" (See post #5) who apparantly did not say what their source was.

L/R is a time constant (in seconds)
X/R is a ratio (a dimensionless number)

I am still waiting for their (L&T switchgear people) reply.
I guess this might be of some use to you, the standard which has the definitions mentioned above-
https://law.resource.org/pub/in/bis/S05/is.iec.60947.1.2007.pdf

Still unsure about what to use for Fault clearing time!
Regards
Girish

I contacted schneider about their device and in reply, I got this attachment (attached). Pl refer point 3 in 'notes' for clarity.

Arcing time by itself seems irelevant. We know it is a component of clearing time, but as long as we know the total, who cares?

What about breakers whose arcing time (or a band in percentages) isn't mentioned in their datasheets? If you have a relay as the tripping device and the breaker attached, you can be sure of (to a good degree) the relay operating time as well as breaker opening times. But, what about the arcing time? For example, please look at the case I posted in regard to L&T breaker, in the beginning of this thread. I don't have the details of arcing time. All I have are the details of release operating time and breaker opening time.
What do you folks do when in such situation?
Thanks and best regards
Girish

Sorry. Upon closer inspection, it would seem IEC does not give you the total. Like jdsmith, I'm ANSI, not IEC.

Interesting that India ignores the IEC copyright, substitutes their own, and then makes it publicly available under "Right to Information."