# Symmetrical Components



## jtucker (Sep 25, 2007)

Wanted to know what those who have taken previous tests thought about how much and how tough were any problems involving symmetrical components. I have seen in other threads that many of you feel that it is imperative to be well versed on symmetrical components. However, the NCEES test and most of the other samples I have, ask very little where sym. components are concerned. How does the real test stack up? Going by the NCEES sample test it looks like most of the fault calc. problems and other power problems can be solved by using simple circuit theory in lieu of more complex methods. Is this the case with the real tes?


----------



## Flyer_PE (Sep 25, 2007)

I took the test in April '07. There were a couple of problems involving symmetrical components but they were pretty simple. There's only so much they can ask in the current format. You need to have a good handle on what the sequences actually represent. One thing to watch for is that the zero sequence current does not transfer to the delta side of a delta-wye transformer. I would also recommend being familiar with how to connect the sequence networks for phase-phase and phase-ground faults. I wasn't impressed with the EERM in this area but my college textbook had a pretty good section on it.

:2cents:

Jim


----------



## Dark Knight (Sep 25, 2007)

jtucker said:


> Wanted to know what those who have taken previous tests thought about how much and how tough were any problems involving symmetrical components. I have seen in other threads that many of you feel that it is imperative to be well versed on symmetrical components. However, the NCEES test and most of the other samples I have, ask very little where sym. components are concerned. How does the real test stack up? Going by the NCEES sample test it looks like most of the fault calc. problems and other power problems can be solved by using simple circuit theory in lieu of more complex methods. Is this the case with the real tes?


JT,

I might be a little off but as far as I remember is important that you understand the concept. I do remember problems about symmetrical components and were not problems to plug numbers into a calc. Where problems where you have to analyze the system and answer questions about the components. Can't tell more because I would be in trouble then. I saw the same type of problem all the times I took the test, and each time they asked a different thing but tested the concept, no numbers involved.

That is my best memory regarding Symmetrical Components. Maybe another EE-Power here had a different experience.

Best of Lucks


----------



## mudpuppy (Sep 25, 2007)

I took the same test Jim did and mostly agree with what he says. I personally thought the EERM was almost useless when it comes to symmetrical componenets.

My experience did differ from BIO's. I only vaguely recall the problems, but I know at least one of them did involve calculations. Here's where I disagree with Jim--I thought this was one of the tougher questions on the exam.

As for whether most of the problems can be solved without symmetrical components, you are right--most of the questions can be solved without them. On the NCEES subject list, symmetrical components together with per-unit and three-phase circuit analysis only average 15% of the power module. If these three subjects are evenly distributed, you're only looking at 5%, or 2 questions, on symmetrical components directly (on average). Note that on any particular exam they may deviate drastically from the subject guide, so YMMV.


----------



## Techie_Junkie_PE_LEED_AP (Sep 25, 2007)

I took the April 07 Power Depth, and from what I remember, I agree that minimal if any calcs for symmetrical components were needed. As said before, KNOW the principles.

Good books to study symmetrical components:

Power Systems Analysis (Grainger/Stevenson)

Power System Analysis (Hadi Saadat) &lt;-- Totally different than the previous

Electric Power Systems (B. M. Weedy)

I'm not suggesting you buy all 3. You might be able to borrow them from a local university engineering library. I did, and brought Gringer/Steveson into the exam. They are very expensive books.

Also, for Power, check out "Electric Machines, Drives and Power Systems" by Theodore Wildi. Great for Motors, Generators, Drives, etc.

Good Luck!


----------

