Complex Imaginary Test 1 Problem 76

[Wildsoldier PE]

This problem ask for voltage drop at point A.

On this problem I assumed that the XL is inductive since is a line....now the problem treat Xl as capacitive by adding the (-) sign for the imaginary component of the complex number. If it is capacitive i think that the problem shall specify that. This is the way I did it...the book did it a little differently but the answer I think its wrong anyway.

[SIZE=12pt]Data provided:[/SIZE]

Per 1000 ft

Rl = .062

Xl = .041

Distance from the transformer 34.5KV/480V transformer to point A = 175ft

Current in the line = 200<25

[SIZE=12pt]Solution:[/SIZE]

Rl @175' = (.062 x 175) / 1000 = .01085

Xl @ 175' = (.041 x 175) / 1000 = .007175

V drop line to ground = Iline x Impedance = (200<25) (.01085 + .007175i) = 2.60<58.47 V

Now we need to change that voltage from line to ground to line to line= 2.60 squre(3) = 4.50 V line to line

The percentage voltage drop = (4.5V/480V) x 100 = .937 %

Any one agrees with me?

 

[Wildsoldier PE]

Well i think with this problem ends my review on the complex imaginary Variation 1 test.

I will post my findings on variation 2 sometime during the weekend or next week.

Using Variation 1 if that was the actual test from NCEES eliminating the ones that i found wrong i could have probably get an 85% correct.

I think i need to calm down a little bid and focus more on my writing because i don't know if this happens to all of you but sometimes when i see in the calculator for example the number 295.....instead of writting that number i write 285 or something similar and sometimes that makes my answer totally wrong....It could be that i'm mentally exhausted between my work and all this!

 

[Insaf]

80% of their questions have no merit ( compared to NCEES sample questions) and lot of errors, wrong answers, missing info etc. I am very disappointed with variation 1.

 

[ElecPwrPEOct11]

Wildsoldier- I agree with your numbers. I double checked the math and continue to get 0.938% Vdrop. I haven't seen this problem changed in any of the erratas, so I guess Complex Imaginary is standing by their solution? I'm not sure who is right but these voltage drop problems are really getting me second-guessing myself. I want confidence going into the test in 2.5 weeks! Are the variation 2 problems better? I haven't tackled them yet.

 

[rick.conner]

I agree. There are several errors with varation #1 plus most of the problems seem to easy. I think there needs to be an errata page on their website and needs to be done today as second-guessing right not is not good!

 

[snerts50]

I agree. There are several errors with varation #1 plus most of the problems seem to easy. I think there needs to be an errata page on their website and needs to be done today as second-guessing right not is not good!

Rick,

I dont know when you purchased the books, but there have been I think 3 errata for Test 1 and 2 for Test 2 since I bought my books, lets say 1.5 months ago? I would email Josh directly and ask him for them. He responds very quickly, at least in my experience.

I have also had some trouble/second guessing with some of these problems, but I feel for the most part that they provide additonal practice for NCEES like problems. I found that the second test was full of more theory then the first and I found myself printing/hunting down more information sources...I have so many notebooks now...

 

[Silkworm]

This question had me 2nd guessing as well. I used the same method as Wildsoldier. They seem to consider the real part of the complex equation for voltage drop only......seems wrong.