what should i study to be good electrical power system protection engineer?

Ahmed, You didn't say what year you are in but here's a starting course list: All engineering core subjects, AC/DC circuit theory, basic and advanced AC machine theory, basic and advanced electric power system analysis, machine labs, linear algebra, and if your school has an intern or co-op program make sure that you get assigned to your local power company.

Alan

I think Alan covered perfectly the core of the requirements but for some calculus and Laplace transformation... I would only add steady and transient states analysis of power systems, although they represent a synthesis of what is already outlined in the above lines.

i am just graduated from my college but i need some help to protection engineer but i don't what should i focus ? what should i read ?

Most power companies will train you to do the job. Most universities do not have a curriculum or courses devoted to protective relaying. The list given above is great to start.

You might want to look into get a copy of Lewis Blackburn's books:
Protective Relaying: Principles and Applications,
Symmetrical Components for Power Systems Engineering

and the Westinghouse Protective Relaying book.

You get used versions relatively cheaply.

thank you

My view is that you should find out what is goal in life before even entering engineering. I have seen people get in to engineering and run music shops, travel business, etc. In these cases they have prevented some other person who was keen on getting engineering education. First find out your interests and aims in life and then decide.

Study everything that interests you. What makes a good engineer better is having people in the field or laboratory or manufacturing screaming at you that you do not understand anything. Once you can begin to understand the perspective of others, then you can really become a good engineer. This is not something they teach in University, but you must go to the school of hard knocks to acquire. Something you should look forward to as these are great opportunities for learning. Do not expect to get to a point where you know everything, but, strive to get to know as many folks in the business as possible so you can know who, how where to go get answers for things you do not know and to confirm those things where you have uncertainty.