# Per Unit Problems



## Byk (Dec 19, 2020)

I am getting ready to start second review of per unit type of problems.

 So I was wondering, other then fault current what type of problems do you expect to be solving in the exam using per unit method?


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## akyip (Dec 19, 2020)

Byk said:


> I am getting ready to start second review of per unit type of problems.
> 
> So I was wondering, other then fault current what type of problems do you expect to be solving in the exam using per unit method?


Questions involving change in per-unit impedance due to a new system base are very common.

If you have the Power System Analysis textbook by Glover/Sarma/Overbye, their transformers chapter (Chapter 3, I think) has a few good examples on using the per-unit method for a simplified analysis of a circuit with multiple transformers (and thus multiple voltage zones).


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## akyip (Dec 19, 2020)

Also, there are questions about solving for a transformer's actual impedance on one given side, given only the per unit impedance and the ratings of the transformer.


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## Byk (Dec 19, 2020)

akyip said:


> Questions involving change in per-unit impedance due to a new system base are very common.
> 
> If you have the Power System Analysis textbook by Glover/Sarma/Overbye, their transformers chapter (Chapter 3, I think) has a few good examples on using the per-unit method for a simplified analysis of a circuit with multiple transformers (and thus multiple voltage zones).


Yeah that make sense.

I am actually just reading that chapter lol. Reviewing the inrush and saturation.


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## Zach Stone P.E. (Dec 21, 2020)

Byk said:


> I am getting ready to start second review of per unit type of problems.
> 
> So I was wondering, other then fault current what type of problems do you expect to be solving in the exam using per unit method?


Hi @Byk, if you haven't worked through our per unit article yet then I highly recommend it. It fills in just every missing gap with the per unit system and helps identify blind spots in this area:

Per Unit Example – How To, Tips, Tricks, and What to Watch Out for on the Electrical PE Exam


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## Byk (Dec 21, 2020)

Zach Stone said:


> Hi @Byk, if you haven't worked through our per unit article yet then I highly recommend it. It fills in just every missing gap with the per unit system and helps identify blind spots in this area:
> 
> Per Unit Example – How To, Tips, Tricks, and What to Watch Out for on the Electrical PE Exam


@Zach Stone, P.E. Your article saved me so much time and trouble (and hair). Thank you for making it accessible to public!


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## Zach Stone P.E. (Dec 22, 2020)

Byk said:


> @Zach Stone, P.E. Your article saved me so much time and trouble (and hair). Thank you for making it accessible to public!


Glad you enjoyed it. It is one of my personal favorites. There a a lot of similar articles on our main website here: http://www.electricalpereview.com/free-articles/


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