# Short Circuit Calcs- which method?



## Platinum (Mar 13, 2007)

Hey guys,

Was wondering which method you guys use when a fault current question pops up in the exam. I learned symmetrical components within the last year, but when i took the exam last october, the short ckt questions they asked did not have any neg or zero sequence impedances given. They didnt seem that complex and i remember they didnt specify what type of fault it was (L-L, L-G?). So if they don't say what type of fault it is, do i assume its a balanced 3-phase fault?

Thanks for your thoughts.


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## Wolverine (Mar 13, 2007)

In the practice problems and elsewhere, I don't remember seeing a symmetrical components problem and the type of fault was usually implicit from the nature of the problem. I've heard rumors of symmetrical components questions before but didn't see any personally in my limited P.E. experience. Anybody else? In contrast, I also don't remember seeing any illumination problems in the NCEES practice problems but did see them elsewhere.


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## Dark Knight (Mar 13, 2007)

Stay tuned. I have some cheat sheets to deal with sckt calculations depending, of course, on the type of fault. Right now I don't remember where I have them but I am sure they are upstairs on one of my binders. Give me a few days and I will get it for you my friend. I remember solving one of the problems on the test using it. You have to have a calc that deals with magnitudes and angles properly. I am sure that once you see the methods it will be easy for you to select which one you will use.

*I'll be back* opcorn:


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## Platinum (Mar 14, 2007)

Luis said:


> Stay tuned. I have some cheat sheets to deal with sckt calculations depending, of course, on the type of fault. Right now I don't remember where I have them but I am sure they are upstairs on one of my binders. Give me a few days and I will get it for you my friend. I remember solving one of the problems on the test using it. You have to have a calc that deals with magnitudes and angles properly. I am sure that once you see the methods it will be easy for you to select which one you will use.
> *I'll be back* :reading:


That would help out a lot Luis, thanks.

There was one symmetrical components question last exam, but it was easy, just solving for Ia,b,c given I0,1,2.

But I'm lost when it comes to fault problems, mostly because i dont know which method to use.

There's point-to-point, MVA, sym comps, Ohmic, etc..... arrgh


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## singlespeed (Mar 14, 2007)

Platinum said:


> That would help out a lot Luis, thanks.There was one symmetrical components question last exam, but it was easy, just solving for Ia,b,c given I0,1,2.
> 
> But I'm lost when it comes to fault problems, mostly because i dont know which method to use.
> 
> There's point-to-point, MVA, sym comps, Ohmic, etc..... arrgh


Make sure you read the question and understand the result that is required. That sounds really obvious, but the mind is great at taking shortcuts and coming to conclusions before you've finished reading the problem!

Have a look at this article The Art of Protecting Electrical Systems, Part 8

I lucked out and didn't see symetrical components on the test I took, but you always need to allow for the fact that it could be there. There really is no way that the test can be comprehensive with just 40 depth questions. So, you need to prepare for anything even though you will only see a tenth of that on the exam.

Also, let me know if you need a good reference for the MVA stuff. I have it in hardcopy, but I could probably find a link to it somewhere on the web.


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## Platinum (Mar 14, 2007)

singlespeed said:


> Make sure you read the question and understand the result that is required. That sounds really obvious, but the mind is great at taking shortcuts and coming to conclusions before you've finished reading the problem!
> Have a look at this article The Art of Protecting Electrical Systems, Part 8
> 
> I lucked out and didn't see symetrical components on the test I took, but you always need to allow for the fact that it could be there. There really is no way that the test can be comprehensive with just 40 depth questions. So, you need to prepare for anything even though you will only see a tenth of that on the exam.
> ...


Yes, any references you have on short ckt stuff would be much appreciated. Let me know if you have a pdf or the link.

Thanks singlespeed


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## odentonpe (Mar 14, 2007)

Luis said:


> Stay tuned. I have some cheat sheets to deal with sckt calculations depending, of course, on the type of fault. Right now I don't remember where I have them but I am sure they are upstairs on one of my binders. Give me a few days and I will get it for you my friend. I remember solving one of the problems on the test using it. You have to have a calc that deals with magnitudes and angles properly. I am sure that once you see the methods it will be easy for you to select which one you will use.
> *I'll be back* :reading:


\

\HEY LUIS DO YOU SOME OF THOSE CHEAT SHEETS AVAILABLE. I WOULD LIKE TO VIEW THEM AND COMPARE THEM TO SOME FORMULAS I HAVE. ANY HELP IS GREATLY APPREICATED. THANKS TO ALL.


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## Dark Knight (Mar 14, 2007)

singlespeed said:


> Make sure you read the question and understand the result that is required. That sounds really obvious, but the mind is great at taking shortcuts and coming to conclusions before you've finished reading the problem!
> Have a look at this article The Art of Protecting Electrical Systems, Part 8
> 
> I lucked out and didn't see symetrical components on the test I took, but you always need to allow for the fact that it could be there. There really is no way that the test can be comprehensive with just 40 depth questions. So, you need to prepare for anything even though you will only see a tenth of that on the exam.
> ...


Nice articles SSpeed


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## grover (Mar 15, 2007)

This was always one of my weak areas, but to be honest, I have no idea what any of the terminology is and simply attacked the PE problems with circuit theory and geometry and the ones on the practice exam and Oct exam were not all that bad.

Of course, I have no idea if I got them right or not


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## singlespeed (Mar 15, 2007)

grover said:


> ... simply attacked the PE problems with circuit theory ...


As Grover says, KVL and KCL really do go a long way...

On the MVA stuff, here are two links, but I will have to scan the hardcopy to pdf since I couldn't find it on the web.

What is the MVA Method?

Extending the simple MVA method


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## singlespeed (Mar 18, 2007)

I've scanned the MVA handout from a class that I took; I'll put it together into one pdf document and post it on Monday. The author is Moon H. Yuen and the full article is available here Complex Short Circuit MVA Method I have only a partial copy.

Another resource that's not too pricey at $23.95 is Short Circuit Calculations the Easy Way


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## chaosiscash (Mar 19, 2007)

Another good place to find short circuit info / cheat sheets is the fuse manufacturers. Bussman and Ferraz-Shawmut put out a lot of free info on both quick and detailed short circuit methods. I used a free book I got from shawmut on the exam, it helped a lot with the minor amount of short circuit stuff I saw. Check out their websites, I'm sure you can find some stuff to download.

Chaos


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## singlespeed (Mar 19, 2007)

The _MVA Method_ pdf file is too large to upload here. PM me with your email and I'll send it to you if you're interested.


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## odentonpe (Mar 19, 2007)

singlespeed said:


> The _MVA Method_ pdf file is too large to upload here. PM me with your email and I'll send it to you if you're interested.



Singlespeed could you email the file. Email address is [email protected] Thanks


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## eng.dork (Mar 19, 2007)

singlespeed said:


> The _MVA Method_ pdf file is too large to upload here. PM me with your email and I'll send it to you if you're interested.



Could you also email [email protected]

Thanks...hopefully this will give me a little more clarification!


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## Computeer (Jan 2, 2014)

singlespeed said:


> The _MVA Method_ pdf file is too large to upload here. PM me with your email and I'll send it to you if you're interested.


singlespeed, curious to know if you still have the MVA method pdf that you listed in this post. If so, please email to [email protected]. Thank you very much!


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## knight1fox3 (Jan 2, 2014)

I believe this is the file that was referenced. At least this is the one I used when I was preparing for the exam:

http://www.arcadvisor.com/pdf/ShortCircuitABC.pdf


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## snickerd3 (Jan 2, 2014)

when I saw the thread title I first thought...what sort of calculations does Johnny 5 have to do?


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## knight1fox3 (Jan 2, 2014)

snickerd3 said:


> when I saw the thread title I first thought...what sort of calculations does Johnny 5 have to do?


A chemical interloper!!!! :blink2:


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## ASG (Jan 2, 2014)

I used the Bussman book.

http://www.cooperindustries.com/content/dam/public/bussmann/Electrical/Resources/solution-center/technical_library/BUS_Ele_Tech_Lib_Short_Circuit_Current_Calculations.pdf


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## ASG (Jan 2, 2014)

Also useful from Bussman for the test:

http://www.cooperindustries.com/content/dam/public/bussmann/Electrical/Resources/solution-center/technical_library/BUS_Ele_Tech_Lib_Voltage_Drop_Calculations.pdf


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## snickerd3 (Jan 2, 2014)

knight1fox3 said:


> snickerd3 said:
> 
> 
> > when I saw the thread title I first thought...what sort of calculations does Johnny 5 have to do?
> ...


darn tootin'. I like to learn new things if i can


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