The exam's biggest topic: Protection

[JohnMdd]

Looking over the exam specs at https://ncees.org/wp-content/uploads/Power-April-2018.pdf, I realized the largest section of the exam is the Protection subheading of the T&D category.

Protection has 13 of the 80 questions - more even than code lookups, which have 12.

I think this category is easy to overlook because you can practice fault current calculations and circuit analysis until your calculator is mad at you, but conceptual questions are often harder to prepare for, and we only have a few days left before Friday the 13th! My suspicion is that the questions in this category are mostly conceptual, so I think it would be great to have a thread about good resources and example problems on this subject. 

I'll start by listing some concepts we should all be familiar with. Anybody, please chime in with an example problem, concept to know, resource to print out, or whatever you have.

: What is the purpose of power system protection?

: What are the major categories of power system protective equipment and schemes used in transmission and distribution systems?

 

[Surf and Snow]

I plan to bring a print out of the GE Art & Science of Protective Relaying protection book that’s long been the go to in the industry. Lots of free PDFs of it out there. 

 

[JohnMdd]

I will be bringing that as well. However, it's a tough read - seems like it was written in the '50s - and I wonder how much modern protection differs from what is covered in that book. Can anyone weigh in on that? Surf'n'Snow, when you say it's the "go to" you sound like you know what you're talking about.

Brainstorming topics/concepts on the Protection subject:

: Different methods of grounding - solid, low/high resistance, reactance - when/where used, pros and cons of each

: Use of different transformer schemes to aid in protection - IE, delta windings are open to zero-sequence currents, Wye grounding resistors limit zero-sequence currents (I think)

 -Speaking of which, I'm very weak on this. Can anyone weigh in on when wye and delta transformer combinations are used for the purposes of fault control?

 

[jshar17]

a comprehensive protection book on the subject is "Protective Relaying: Principles and Applications" by Blackburn. It's quite dense though. To answer your last couple of questions: delta windings trap zero sequence current as there is no path to ground, they do not pass through the transformer to the secondary. A neutral grounding resistor in a wye system is used to limit fault energy in the form of I^2t, thereby reducing the time fault current can damage the equipment.

 

[blewis216]

Would highly recommend taking in a copy of Blackburns book. I took a copy with me into the test and I used it often. As for how applicable the GE protection book is, remember the test is testing you on relaying concepts. The old school relaying schemes make concepts more apparent due to the fact that they are simplistic in nature (you only have PTs and CTs, no modern logic groups, counters, math variables, and whatnot). I'd say taking in the GE book or the Blackburn book would be a must.

 

[BirdGrave]

Does the Graffeo book cover relay protection in a manner adequate for the exam?

 

[blewis216]

Graffeo is good at the basics but I would highly recommend bringing something more in depth to the exam. Especially since the number of protection questions has increased. An additional benefit to the Blackburn book is that it covers things like system grounding, symmetrical components, instrument transformers etc. I would in general not rely on Graffeo to be your only reference for any topic. It is good but has holes in just about every topic.

 

[BirdGrave]

Graffeo is good at the basics but I would highly recommend bringing something more in depth to the exam. Especially since the number of protection questions has increased. An additional benefit to the Blackburn book is that it covers things like system grounding, symmetrical components, instrument transformers etc. I would in general not rely on Graffeo to be your only reference for any topic. It is good but has holes in just about every topic.

Yea I went ahead and got Blackburn for overnight delivery just to be on the safe side.

Does Blackburn have a good index of terminology/page numbers in the back, or should I look to spend some time tabbing it?

 

[blewis216]

I'd recommend tabbing either way, there is a lot of info there. In general I'd try to tab every reference book you bring as much as you can. But blackburn is very information dense and it has a lot of technical info so to prevent yourself from getting lost in the weeds I'd tab out specific things you know you'll use. Now, if you do happen to forget to tab something I found blackburn's book to be one of the better indexed books I brought.

 

[BirdGrave]

I'd recommend tabbing either way, there is a lot of info there. In general I'd try to tab every reference book you bring as much as you can. But blackburn is very information dense and it has a lot of technical info so to prevent yourself from getting lost in the weeds I'd tab out specific things you know you'll use. Now, if you do happen to forget to tab something I found blackburn's book to be one of the better indexed books I brought.

If I may ask more broadly, what resources did you find particularly helpful on the exam?  So far my camping pack is provisioned with

Graffeo

Wildi 

Grainger 

NFPA 70 / NFPA 70E

NESC

School of PE Power notes 

EngProGuide formula sheet

Complex Imaginary 1-4

Both the latest and preceding copies of NCEES Practice Exam

Ugly's 

and now Blackburn.  

I wasn't sure if there were any glaring omissions on my part or something I haven't listed that I should be looking to pick up because you found it useful.  Thanks for your input.  

 

[blewis216]

I'd say you're in good shape with those. It seems pretty similar to what i took and I felt just fine about what i had. It looks like you probably have a resource on every topic in the test spec but double check that. If you don't have a reference on it then either grab one cheap or print off the wiki page for the topic.

The only other one I took that you don't have is Mohan's power electronics book... I only had that because I was beaten up pretty badly by all of the Power electronics questions on practice exams.

 

[BirdGrave]

I'd say you're in good shape with those. It seems pretty similar to what i took and I felt just fine about what i had. It looks like you probably have a resource on every topic in the test spec but double check that. If you don't have a reference on it then either grab one cheap or print off the wiki page for the topic.

The only other one I took that you don't have is Mohan's power electronics book... I only had that because I was beaten up pretty badly by all of the Power electronics questions on practice exams.

Did you find you used Mohan during the exam, or did it end up being extra?

 

[blewis216]

I can't remember if I did... which probably is a good indicator of how useful it was.

 

[blewis216]

But is was a nice comfort to have a crutch on a topic that brutalized me as bad as it did

 

[JohnMdd]

After reading the suggestions above, I found a PDF of the 2006 edition of Blackburn online. I've been reading it and have ordered it printed and bound at Office Depot. I'll be bringing it, but I don't have a lot of time to familiarize myself with all its content in the 10 days I have left. It sounds like tabbing is the recommended strategy when you don't have time to actually read the sections...

 

[BirdGrave]

But is was a nice comfort to have a crutch on a topic that brutalized me as bad as it did

Outside of the obvious codebooks that one needs (NEC, NESC), what was the go-to or the primary resource that you found most helpful on the exam?

 

[blewis216]

Honestly for all it's holes I'd say graffeo was the most used. But I also used the PPI book a lot too. There are a whole lot of questions you can answer in under a minute by just looking up a formula in one of those two books.

 

[argo97]

Agree.  Most used was Graffeo and the School of PE notes.  

 

[Surf and Snow]

Well, I got lucky today and found a hardcover copy of Blackburn’s protective relaying book (2007 ed.) at work today, so I’ll be bringing that now. Can’t beat free. Might as well since protection is now the biggest question set on the exam this year. 

 

[steezmo]

I used Graffeo - studied  for two weeks. Walked in the exam with that and the NCEES handbook and got a 90. TX gives scores. Would not recommend bringing too many specific protection references into the exam. The art science of protective relaying is a good book, may want to check out Buff Book™— IEEE STD 242™-2001, Recommended Practice for Protection and Coordination of Industrial and Commercial Power Systems. 

Do you do arc flash or coordination studies at work?