Committee Chair

Kobet, Gary L.

Committee Member

Eltom, Ahmed H.; Karrar, Abdelrahman


Dept. of Electrical Engineering


College of Engineering and Computer Science


University of Tennessee at Chattanooga

Place of Publication

Chattanooga (Tenn.)


The main purpose of power system protection is to remove faults from the system as soon as possible so minimum damage happens to the transmission line or other equipment connected to the line. Tennessee Valley Authority (TVA) planners want to add multiple breaker-in/breaker-out stations on a two terminal transmission lines to reduce the number of Customer Connection Point Interruption (CCPI). This paper discusses the difficulty of setting up the zone distance relays and overcurrent relays when multiple breaker-in/breaker-out stations are added on the transmission line. It explains how many breakers can safely be added without compromising the zone 2 time delay of 50 cycles (limit imposed by TVA), how to set distance relay for phase faults and instantaneous overcurrent as well as time overcurrent relay for ground fault. It makes recommendation for not placing the breaker-in/breaker-out stations at a certain distance on transmission line and also talks about the maximum line loadability according to NERC standard PRC-023 when zone 2 of the distance element is set higher than 130%.


Gary Kobet: You are one of the best teachers I have had in my life. You are always willing to share your knowledge, always available to explain things if a student is willing to listen and curious and provide materials for the students. I am fortunate enough to come back to Chattanooga, TN and study two courses you teach at University of Tennessee at Chattanooga. It took many twist and turns along the way but I believe I have found what will make me happy in my career. Now I just have to find someone who is willing to pay me for doing the relay calculations. I will never forget the lesson you hammered during the class: “Ask questions until you understand” which is a very important lesson because not many teachers encourage this. You have this uncanny ability to come down to meet where students are and explain things in a way that is easy to understand. I am forever grateful to have you as my teacher, mentor and thesis advisor. I hope you would write a book about relays so novice like me can have one great reference book after you retire. Another lesson you taught me recently is to not be afraid to say ‘NO.’ I chose you as my thesis advisor because I knew no matter what grade I make, you would be fair to me and I would learn a lot of new things along the way. It has been a great journey through this thesis and I sure hope to see you around and keep learning from you in the next few years. Thanks for being the kindest and most available teacher to your students. I sure hope one day I pay forward the kindness you have shown me to someone else. Dr. Eltom: You might not remember this but you said” Just do it” and here I am today finishing my M.S. Thanks for listening to my sad stories ,showing me kindness and providing encouragement.


M. S.; A thesis submitted to the faculty of the University of Tennessee at Chattanooga in partial fulfillment of the requirements of the degree of Master of Science.




Electric power systems; Electric power distribution


Relay coordination; Multiple breakers; Zone distance protection; Ground fault protection; 50N settings; 51N settings

Document Type

Masters theses




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