NCEES Practice Exam #12

[Gman]

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

 

[DLD PE]

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

 

[Gman]

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

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

 

[akyip]

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).

 

[Zach Stone P.E.]

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!

 

[yaoyaodes]

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!

Why A is correct? and why E is incorrect?

 

[Rafis]

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.