I'm chimming in based on my recent experience with the April exam. Although there is a lot more to the exam than what I'm saying now, spend a decent amount (i.e., a lot) of time learning the NEC and another fair amount learning the NESC. There was some emphasis there on the exam and if you go in unprepared, you will waste a lot of valuable time searching through these voluminous references. Also, know something about the health and safety of electrical work. I know that most of us don't think about shock, burns and electrocution but these are topics that may come up. They are also topics of great importance if you are really working with power systems. I'm not preaching but just saying that where I work electrical accidents have happened and being a Power PE has real implications. Two fold benifit of studying this topic: you are better prepared for the exam and, vastly more importantly, you are a better engineer safeguarding the well being of yourself and your coworkers. For example, check out this as a reference:
http://www.pshsa.ca/wp-content/uploads/2013/11/EELPWAEN0413-Electrical-Safety-Handbook_20131.pdf
Best to all,
Bruno
http://www.pshsa.ca/wp-content/uploads/2013/11/EELPWAEN0413-Electrical-Safety-Handbook_20131.pdf
Best to all,
Bruno