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roy167

Why isn't this forum active?

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Hello future test takers, don't you want to pass? I would think at least someone would be discussing something every few days with 4 months left? Unless there are not many Power PE takers this fall. 

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The power exam is super easy so test takers don't really need to study.

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That’s funny...trolling doesn’t usually start until a few weeks before the exam.

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Hello future test takers, don't you want to pass? I would think at least someone would be discussing something every few days with 4 months left? Unless there are not many Power PE takers this fall. 

I recently started studying here. The worst part about failing the exam is getting back on that horse to study all over again.

I read somewhere here that Electrical PE Review is a good place to set foundation for the “why” of things. So for new/repeat test takes.... highly recommend the online course


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Greetings,

Although I may not be active in the forum, I have been putting consistent studying while reading past posts related to the Power Pe Exam (has been extremely helpful in directing me towards approach, resources and over all motivation).

I do appreciate Roy publicly expressing his/her concern for those of us who are in the come-up for the exam (which in truth is a surprise to me - Roys’ response to my simple doubts to my simple questions have been callously delivered and as a result have refrained from further communication with him/her - nonetheless Roy thank you)

I would like to give a special shout out and appreciation to Eduardo L - he has consistently been a great help to me (incredible person & extremely knowledgeable). Justin K. from EngPro - thank you brother for clarifying doubts I may have (prompt/concise/intellectual person)

Roy - should you feel there are topics of focus or any sort of hints that may be of help to us, please enlighten us with your experienced knowledge (NEC/Protection from what I’ve investigated being the key topics ).

As for the rest, please post questions/doubts and I will do all I can to help. We rise together.

Moises F.

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1 hour ago, wiliki said:


The worst part about failing the exam is getting back on that horse to study all over again.
 

 

Trust me, I can see how it can be to get on that horse again.  I firmly believe those who pass on the subsequent attempts is much more resilient, deserve much more kudos than the first time time passers.  I pray for your success this time.  

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Because its about 5 months away and reading posts by you annoy me so I stay in the other sub-forums. 

People can and do pass without this forum so it really doesn't matter that there aren't any posts here so your subtle shame-y worded post is unnecessary. 

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2 hours ago, LyceeFruit said:

reading posts by you annoy me so I stay in the other sub-forums. 

 

You would need this sub forum more than me. So I think you should stay here and I won't post any more in this sub forum. All the best. 

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Good-morning all,

From the attached problem, can anyone help me find a reference as to where:  "impedance of the new transformer will be reduced by the square of the voltage change" comes from?  

I initially solved this problem by Znew = zold * (Vold/Vnew)^2 but I am assuming it will not work because it applies to Zpu.

 

Q-32.PNG

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4 hours ago, FelizENG said:

Good-morning all,

From the attached problem, can anyone help me find a reference as to where:  "impedance of the new transformer will be reduced by the square of the voltage change" comes from?  

I initially solved this problem by Znew = zold * (Vold/Vnew)^2 but I am assuming it will not work because it applies to Zpu.

 

Q-32.PNG

I believe Z(old) and Z (new) is confusing and I believe I brought it to Justin's notice . Z old in the 1st line should be Z new. 2nd line, Z new and Z old values do not match.  

Go by the basic formula  S = (V^2 /Z)

S1 = V1^2/Z1 and S2 = V2^2/Z2

subscript 1 = 480 volts or old voltage

2= 400 volts or new voltage

 v1^2/z1 = v2^2/z2 ( since reactive power KVAR is same)

plug and chug, you should get z2 , z1 is already given 

difference = z1-z2

 

In real world , impedance should remain same for the given Kvar rating and if you apply different voltage than rated then you should see corresponding change in Kvar??? Problem needs to state some how or give an indication that the kvar rating is the same in both cases. 

Edited by roy167
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Correct - I had: 

*Znew = 10 angle(30)  x (400/480)^2 = 6.94 angle (30)

*Zdiff = Zold- Znew = 10 angle(30) - 6.94 angle(30) = 3.06 angle(30) 

 

Thanks Roy - I don't think the correction was made on the guide.  

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I haven't been posting on here because I've been so busy studying and taking practice exams.  If I get stumped on a question, I can usually find the answer somewhere on here or on YouTube.  I spent more time on here before taking the October '18 exam, but not this time.  I didn't take it this past April (we were busy selling our home among other things) but I'm taking it for the second time in October.  I have all the material from Zach's course I took from the first go-around so I feel well-armed at this point.

There is one particular question I'm not sure I got right last October, and I'm pretty sure I've seen completely opposing answers from the reference materials I have.  I'm just not sure how to ask the question without getting flagged by the NCEES.  In other words, I don't know how to ask the question in a way that's different than it was on the exam.

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6 minutes ago, MEtoEE said:

I haven't been posting on here because I've been so busy studying and taking practice exams.  If I get stumped on a question, I can usually find the answer somewhere on here or on YouTube.  I spent more time on here before taking the October '18 exam, but not this time.  I didn't take it this past April (we were busy selling our home among other things) but I'm taking it for the second time in October.  I have all the material from Zach's course I took from the first go-around so I feel well-armed at this point.

There is one particular question I'm not sure I got right last October, and I'm pretty sure I've seen completely opposing answers from the reference materials I have.  I'm just not sure how to ask the question without getting flagged by the NCEES.  In other words, I don't know how to ask the question in a way that's different than it was on the exam.

Post your conflicting, publicly available, source material.

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Hello.  I was having a discussion with Roy through PM regarding "Differential Protection of a Three-phase Wye-Delta or Delta-Wye" and wanted to upload 2 related problems.  

Roy as I had mentioned, 3-Ph  Wye-Delta or Delta-Wye connected Transformers produce 30 degree phase shifts in Line Currents. 

Therefore, CTs must be connected:

  1. On Wye side of the Tx in Delta
  2. On the Delta side of the Tx in Wye.

As a result, CT secondaries that are in Delta must be multiplied by root 3 to obtain current CT secondary current (as shown in problem 2)  

Please refer to the image I have uploaded:

  • After inquiring/speaking with author of Problem 1, the problem will be revised to indicate 30 degree phase shift is neglected.

 

  • Problem 2 shows the correct or rather common approach in finding the CT secondary current connected in delta.   
     

Thank you and please make me aware if my understanding is not correct.  

DifferentialTxProtection.thumb.PNG.7ee357d6af4f3278ab67a8db4297ff4f.PNG

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17 hours ago, fyrfytr310 said:

Post your conflicting, publicly available, source material.

At this time, I'm choosing not to risk it.  I'm going to ask the author of one of the sources to confirm what is in the notes.  Maybe I can get to the bottom of it then.

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Fair enough.  I think you would be ok as long as you don't reproduce the test material but I understand the risk aversion.  

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