# NCEES Practice Exam #12



## Gman (Mar 22, 2021)

Why is the zero-sequence current phasor equal in magnitude and displaced by 120 degree? Shouldn't it be same as zero-sequence for voltage phasors which are same in magnitude and in phase? Thank you in advance


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## DLD PE (Mar 22, 2021)

EDIT: See below. I actually had the corrected version so I may have misled the OP.


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## Gman (Mar 22, 2021)

The answer key says A,B,D so that's wrong right? A is incorrect but B and D are?


DuranDuran said:


> It's an incorrect statement, therefore not one of the correct answer choices.


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## akyip (Mar 22, 2021)

Gman said:


> View attachment 21490
> 
> The answer key says A,B,D so that's wrong right? A is incorrect but B and D are?


Yes. NCEES released an errata clarifying and correcting this (and I think 3 other problems).

Zero-sequence phasors have the same magnitude and same phase angle. There is no angular displacement between the zero-sequence phasors.

Positive-sequence phasors have the same magnitude, but 120-degree angular displacement rotating in the direction of ABC.

Negative-sequence phasors have the same magnitude, but 120-degree angular displacement rotating in the direction of ACB (or CBA).


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## Zach Stone P.E. (Mar 22, 2021)

Check the errata, or click on "PREVIEW" of the book when you log into your NCEES account. This was a mistake that has since been corrected in newer versions of the NCEES CBT Power PE Practice Exam:

account.ncees.org > Exam Prep > PE > PE Electrical and Computer: Power Practice Exam > View Product > Preview this book now

The answer was changed to just A and B since C is incorrect.

Zero sequence phasors are all equal in magnitude but have a zero-degree displacement angle between phases since the angle of each zero-sequence phasor is the same.

Edit - Beatin by @akyip!


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## yaoyaodes (Jun 7, 2021)

Zach Stone P.E. said:


> Check the errata, or click on "PREVIEW" of the book when you log into your NCEES account. This was a mistake that has since been corrected in newer versions of the NCEES CBT Power PE Practice Exam:
> 
> account.ncees.org > Exam Prep > PE > PE Electrical and Computer: Power Practice Exam > View Product > Preview this book now
> 
> ...


Why A is correct? and why E is incorrect?


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## Rafis (May 19, 2022)

yaoyaodes said:


> Why A is correct? and why E is incorrect?


The errata revised the multiple choices so A is the The Three Positive sequence Voltage phasors instead of the Zero Sequence current phasors, making the solution description correct.


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