“Relay protection of overhead transmission lines. Recent approaches of differential protection” by Invited Lecturer – Tomislav Rajic (ETF Belgrade, Serbia)

Dear Colleagues,

The 4th seminar of the Spring Friday Seminar Series 2022 “Relay protection of overhead transmission lines. Recent approaches of differential protection” by Invited Lecturer – Tomislav Rajic (ETF Belgrade, Serbia)was given on May 13th.



Transmission lines Overhead lines and cables are one of the most important elements of the electric power system because they enable the transmission of electricity from producers to consumers. Several protection methods are used for secure more reliable and safe energy transmission. High voltage lines include both possible directions of the power flow Protection of these lines are more complicated especially because of this fact. Distribution networks had not had those possibilities for a long time. Hence, the protection was simple and easy. When independent energy sources took the place in distribution network, more complicated protections had to be installed. Protection hronology, from the simplest overcurrent towards to more complicated as a distance protection will be presented with all disadvantages. The basic part of the lecture is about the fastest and very reliable protection – differential protection. This protection must take part even in the distribution network because of the load flow direction changing. Several recent and most interesting ideas about realisation of this kind of protection will be presented briefly. Emphasise is on those ideas which have taken the place in practice. Two great manufacturers of the relays include these ideas in their own algorithms. During the time of use, even these two algorithms showed disadvantages. This lecture will show the results of the recent research about this topic on School of Electrical Engineering in Belgrade. The new idea of current differential protection will be presented and compared with two mentioned algorithms. The new algorithm simplicity leads to fast and correct fault detection in all circumstances that could be reason for maloperation of the others.

About the author

Tomislav Rajić was born in 1989 in Belgrade. Bachelor and Master degree took at the School of Electrical Engineering, University of Belgrade, Serbia. He began PhD studies at the same university and joined as Assistant at the same time. The relay protection is his major field. He received PhD degree with thesis entitled ”New approach in realization of longitudinal differential protection of overhead lines”. His areas of interest are: relay protection, power system analysis, grounding systems and electromagnetic compatibility.

In the following file you will find an introduction and a detailed timetable of Friday Seminar Series: