EE student with focus on Power Systems here. I found a great website that breaks down in detail about power systems, substation engineering, guidelines for PE exams and many other topics are covered. For students like me or professionals wanting to brush up on their knowledge, this website is a must visit! Hope this is of big help to some of you!
The website is www.peguru.com
The writer also lists a few good books for in depth understanding of the subject! Only if there were quizzes, which I've suggested and if some of you, if interested, would like quizzess from him, send him a message :)