ECN Forum
Posted By: DennisVan kasc - 11/16/10 06:03 PM
what is the difference between kasc ans kaic?
Posted By: HotLine1 Re: kasc - 11/16/10 08:22 PM
Dennis:
Welcome to ECN Forums, from the east coast!

'SC' is referred to by some methodology intermixed with AIC/KAIC

'SC' (SCA) is short circuit amps, or available short circuit amps.

'SCA' is referenced many times in Bussmann Point-to-Point calc methods.

Scott35 may have a more detailed definition!
Posted By: Tesla Re: kasc - 11/16/10 10:28 PM
kAIC...

kilo Amps Interrupting Current...

A fuse rating ( to a voltage limit ) of blocking/ stopping power against over current flow.

Obviously, this is in reference to A/C systems with infinite bus character.

-----

kASC

kilo Amps Short Circuit

This is a metric related to the inverse impedance of a system.

It is calculated based upon what current can flow through from the Poco side into a shorted distribution system PLUS the instantaneous back EMF available from induction elements ( motors, chiefly ) and capacitive elements ( pf correction capacitor banks, chiefly ) when a 'bolted' short circuit occurs across a customer's main bus.

Because the system has a shifting impedance throughout and back-EMF changes with motor state the typical calculations are done WRT worst case fault energy thresholds.

A classic would be catastrophic transformer failure due to physical impact. Marc once related such a fiasco: a load shifted while on a massive forklift. Both load and lift tumbled into a rack of massive XFMRS. They went off like bombs. In a bolted short mode EMF from all associated systems drained into the short producing a plasma explosion, followed by a nasty fire.

Months later the rebuilt, redesigned system used COORDINATED fuses to protect against both Poco side energy and back-EMF coming back from all of the rotary loads.

They even threw in some bollards!

----

For most situations rotating loads are trivial ( homes, small businesses ) but it gets interesting in industries that have the works.

Naturally, no electrician's calculations are going to satisfy: the insurance company will insist on an EE -- who carries a nice E & O Policy.

( E & O = Errors & Omissions = professional screw-up insurance )
Posted By: JBD Re: kasc - 11/17/10 01:21 AM
Originally Posted by Tesla

kASC

kilo Amps Short Circuit

This is a metric related to the inverse impedance of a system.



Say what????

I have been working with fault currents since 1974.
Never in my life have I heard of kASC or the "inverse impedance of a system" with your description.

Available Short Circuit Amps (SCA) is always supposed to include the short circuit amps from all sources, utility, generators, motors etc.

Most likely someone has transposed some letters, and used a numeric suffix as a prefix.
Posted By: Tesla Re: kasc - 11/17/10 03:15 AM
Impedance...

The LOWER it goes the GREATER the instantaneous short circuit Amperage will flow.

Hence, an inverse relationship.

An infinite bus at a given voltage is dominated by the impedance of its elements from sources to the bolted fault.

QED
Posted By: JBD Re: kasc - 11/17/10 05:43 AM
Originally Posted by Tesla
Impedance...

The LOWER it goes the GREATER the instantaneous short circuit Amperage will flow.

Hence, an inverse relationship.

An infinite bus at a given voltage is dominated by the impedance of its elements from sources to the bolted fault.

QED


The term inverse is almost irrelevant to your description. Of course, for a given voltage, current and impedance have an inverse relationship. But that relationship has nothing to do with the phrase kASC.

Amps, Short Circuit is not a common expression.

In the 'power systems study' world, an infinite bus source is one that can deliver an unlimited amount of current into a fault. There is no need to add additional sources of fault currents to an infinite bus.
Posted By: Tesla Re: kasc - 11/17/10 09:39 AM
One must look Left and Right.

In fault conditions the amps are coming up the line ( the Poco ) and back from loads ( back-EMF )

The expression 'infinite bus' is a term of art. Obviously, even the entire US grid is not infinite. However, for the purposes of the calculations infinite bus means that the delivered voltage is not considered to sag. Yeah, it's idealized.

Because of the interposition of magnetic circuits within our infinite bus THEIR impedance becomes huge in short circuit calculations.

Ditto for 'rotary transformers' ie 3-phase induction motors and the like.

Posted By: JBD Re: kasc - 11/17/10 03:10 PM
Originally Posted by Tesla
One must look Left and Right.

In fault conditions the amps are coming up the line ( the Poco ) and back from loads ( back-EMF )

The expression 'infinite bus' is a term of art. Obviously, even the entire US grid is not infinite. However, for the purposes of the calculations infinite bus means that the delivered voltage is not considered to sag. Yeah, it's idealized.

Because of the interposition of magnetic circuits within our infinite bus THEIR impedance becomes huge in short circuit calculations.

Ditto for 'rotary transformers' ie 3-phase induction motors and the like.



Way to go.
String together all sorts of fancy words, throw in enough minimum truth, and everyone will think you are an expert.

But what does this all have to do with the OP term of KASC?
Do you have any references to show that this is a term used in our industry?
After 35 years of doing short circuit studies in the US, maybe I am just out of touch the rest of the electrical world.
Posted By: DennisVan Re: kasc - 11/17/10 05:10 PM
Thnaks guys, I think the engineer made a typo error!
Posted By: Tesla Re: kasc - 11/19/10 11:09 AM
Uglies...

Page 58 59

Amazingly...

Uses virtually identical terminology.

I s.c. = Amperes Short Circuit.

Further inspection shows this value to be always in the THOUSANDS.

i.e. kilos.

QED

That an EE or two decides to write the SAME term in a trivial variation....

Oh, well.

Cheers.
Posted By: Tesla Re: kasc - 11/19/10 11:30 AM
Dennis...

You might pick up the phone and ask the EE.

They'd be delighted to hear from a field electrician.

The very few time I've had the pleasure of meeting the EE's who wrote my plans it was happy times and fellows well met.

THERE IS NO ONE AN EE WOULD RATHER CHAT WITH THAN THE DUDE IMPLEMENTING HIS WORK.

It gets them totally stoked. You realize their scheme -- and it may be a thing of beauty. Certainly, that's what MY EE's thought.

Yeah, cameras were popping everywhere. The installed work became part of THEIR portfolio, too.

BTW, ALWAYS photo your work. It is a fantastic sales/ job securing gambit. Now that we are in the digital camera age, it is expected.
Posted By: JBD Re: kasc - 11/20/10 12:27 AM
Originally Posted by Tesla
I s.c. = Amperes Short Circuit.


Absouletly, but it is not refered to as ASC.
Just like Ibf = Amperes Bolted Fault, is not called ABF.

My point has been kASC is not a commonly accepted or understood acronym.
Posted By: HotLine1 Re: kasc - 11/20/10 03:02 AM
JBD:
Yes, as you say, kASC is not a term that is normally used, and can be tough to grasp what it is being used for.

When I read the OP, I made an assumption that the OP made a typo, or someone who provided him info or documents made a typo.

Acronyms can and do get confusing, as above posts interchange from Ohms law symbols (letters) to terms we use in the trade. ie: "I", "E", "R", "P" that are within Ohms Laws, and "A" "V" 'Omega symbol' and "W" that are trade.

Hopefully, your point above is accepted by all.

Posted By: mikesh Re: kasc - 11/24/10 11:11 PM
KASC Thousands of amps of available short circuit current

KAIC Thousands of amps Interupting Capacity. The ability of the overcurrent device to stop the the fault.
So a code fuse is 10 KAIC
an Hrc fuse is 100 0r 200 KAIC.
Posted By: JBD Re: kasc - 11/26/10 09:25 PM
Originally Posted by mikesh
KASC Thousands of amps of available short circuit current...

Is this a Canadian acronym?

It is definitely not commonly used in the US; we say kSCA.
I do not believe it is common in Europe either.
Posted By: Tesla Re: kasc - 11/29/10 07:14 AM
JBD...

The term comes from Bussman...

And their little known calculations in Uglies...

This has been discussed up thread.

Times, terms ...

They do change.

As an identifiable calculation...

It's been out there for quite some time.

Must you stand as King Knute damning the tides?

It's not as if I or any poster here came up with the notation.

Instead, it comes from the premier manufacturer of fuses.

I understand that as of 2011 the Code expects this calculation to be done across the board.

BTW, if you were a real historian of scientific/technical notation then you'd know of the CONSTANT shift of terms of art. If you were to read Newton - you'd choke on his writing. The Physics is the same -- but NOT the notation.

Against the influence of Uglies and Bussman...

Your purity of notation must be for nought.

INRE your assumption that I was wildly off base: I think I've answered that.

The purpose of ECN is to expand knowledge...

NOT to get into personal disputes and putdowns.

That kASC is, in your view, not a correct/traditional notation does not mean that the term is not in use -- constantly, if Bussman is to be followed.

----

From here on, such calculations are destined to be ever more common. I don't particularly care WHAT the notation is.

But that kASC/kSCA point to the SAME metric works for me.
Posted By: JBD Re: kasc - 11/30/10 05:35 PM
Originally Posted by Tesla
That kASC is, in your view, not a correct/traditional notation does not mean that the term is not in use -- constantly, if Bussman is to be followed.


I perform short circuit calculations for my living as a power systems engineer. I have been doing so for many years and have never come across the acronym kASC. I do not find it in my copy of UGLY'S (but it is the 1990 edition. It is not in my copy of Bussmann's SDP dated 2002. I do not see it in SKM's Power tools for Windows (one of the premier power system software programs) nor in any of IEEE's color books.

I just downloaded Bussmann's latest copy of SPD, and searched for both ASC and KASC, and neither was found.

I stand by my statement that KASC is not, currently, a commonly used acronym within our industry.
Posted By: HotLine1 Re: kasc - 11/30/10 08:09 PM
Gentlemen:

I think by now, the popular opinion is that the acronyn "KASC" was probably a typo within the OP, or a transposition.

As JBD said above, the term is NOT within the Bussmann literature, as I use there literature (with permission) within a Fault Current CEU that I present. I also use 'UGLYS' within a class I teach at a local Vo-tech, and to my knowledge, it is not within same either.

All that said, let us NOT turn this thread into a 'flaming' issue!

Posted By: mikesh Re: kasc - 12/01/10 12:10 AM
Originally Posted by JBD
Originally Posted by mikesh
KASC Thousands of amps of available short circuit current...

Is this a Canadian acronym?

It is definitely not commonly used in the US; we say kSCA.
I do not believe it is common in Europe either.


No not Canadian, just an answer to the original Question.

Schneider Series rating guide uses KA Sym
Bussman fault current calculator uses SCA (Short Circuit Amps) and ASC Available short circuit current
Cutler hammer's series rating guide is using KA Sym.
GE series rating guide only seems to refer to XXX Amperes IC as the term.


It seems the terminology has gained prominence in the discussion and has taken a life of it's own. Rather than argue about whether it is a defined term or not lets accept it is becoming code language (or not) and address the question. Is the question ambiguous because of the terminology? If that answer is yes then I appreciate the point of defining the term in a particular way. I think every one in the discussion knows what is being asked here.
Posted By: JBD Re: kasc - 12/01/10 01:38 AM
Originally Posted by mikesh
Rather than argue about whether it is a defined term or not lets accept it is becoming code language (or not) and address the question. Is the question ambiguous because of the terminology? If that answer is yes then I appreciate the point of defining the term in a particular way. I think every one in the discussion knows what is being asked here.


I have just looked at the Bussmann downloadable Short Circuit Calculation software, it does not use this acronym.

Proper usage of acronyms and terms is very important. There are many questions that are answered inappropriately because the parties mis-understand the terms being used.
Posted By: HotLine1 Re: kasc - 12/09/10 02:29 AM
JBD:

Not to awaken a sleeping dog, but here is another acronym from The opposite side of the world. From Trumpy from the South Island of New Zealand.

"PSCC= Prospective Short Circuit Current."

It's within this thread, relating to a switchgear explosion at a strip mall.

https://www.electrical-contractor.n...565/Re_Watch_them_meters.html#Post197565
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