Hang in there and try again. I failed once a year ago, passed this April.
Here is what I changed in my studying:
1) less practice problems (I used the NCEES study guide, Graffeo below and Spin Up, about 1/2 of the problems)
2) bought and studied this book, cover to cover.
The Electrical Engineer's Guide to Passing the Power PE Exam ,Alexander S Graffeo, PE
It has so much information regarding odd topics and obscure information regarding power systems.
3) I built up a better archive or synopsis of formulas and example problems.
4) Learned the MVA method for fault current calculations:
short circuit abc by moon Yuen
5) I started studying earlier, around Thanksgiving last year. My advice, start studying again soon,
you will need to keep everything fairly fresh in your head.
6) Remember, if you miss a sample problem, figure out why and rework the problem a few days later to validate your memory.
I made sure I understood the theory behind the problems, not just how to solve that particular problem.
7) I brushed up on basic single and three phase power circuits and thoery, some things I don't use in my job.
I also studied the NEC code more in depth than I did last time. Mike Holt's website is a great reference, I used his online tests for free to help out.
www.mikeholt.com
8) Finally, I didn't take any timed tests, I don't seem to have issues with time on these type of exams.
There are parts of each exam that I didn't know, but using the steps above, I was able to reduce the number of questions I had to guess on by at least half this last time.
I used the Graffeo book on about 1/3 of my questions.
My books:
The Electrical Engineer's Guide to Passing the Power PE Exam, Alexander S Graffeo, PE (used alot)
Electrical Engineering Reference Manual for the PE Exam, 5th Edition, Jun 1997, by Raymond B. Yarbrough (used on 3 questions)
Power Systems Analysis, Grainger, 1994
Schaum's Outline of Electrical Power Systems, 1989,Syed Nasar (not much use, but it may have given me one answer)
Power Systems Analysis and Design, 2007,
J. Duncan Glover and Mulukutla S. Sarma
Electric Machinery Fundamentals, 2003, Stephen Chapman ( I used this one a lot on the exam)
NEC 2014
NFPA 70e 2012
Ugly's 2014
MVA Method - Short Circuit ABC, Moon Yuen - paper
Transformer maintenance documents from ABB and GE
Protective Relaying White Paper from ABB
Personal Notebooks for NCEES Practice Problems with solutions, Formula Sheets, Worked problems and examples
Good luck!