The aim of this technical article is to cover the most important principles of four fundamental relay protections: overcurrent, directional overcurrent, distance and differential for transmission lines, power transformers and busbars. Applications of the concepts to accepted transmission line-protection schemes are also presented. Many important issues, such as coordination of settings, operating times, characteristics of. Power System Protective Relays: Principles & Practices Protective Relays - Technical Seminar Nov 2016 - Copyright: IEEE 1 Power System Protective Relays: Principles & Practices Presenter: Rasheek Rifaat, P. Eng, IEEE Life Fellow IEEE/IAS/I&CPSD Protection & Coordination WG Chair Jacobs Canada. Numerical Relays: Digital relays that use microprocessors, offering advanced protection and monitoring features. Contents: For simplicity in explaining the key ideas, we. Long term cost reduction (TCO) for trainings and maintenance by reduce variety of relays A fast and selective arc fault mitigation for air-insulated LV & MV switchgear and Relion protection and control relays and sensor technology protect staff and plant facilities for many years. Figure 7 Overcurrent Protection of Radial Power System For setting the pickup values and the selectivity clearances between the time overcurrent relays for backup protection, there are four criteria to consider:.