One of the most complex disciplines of electrical engineering is power system protection which requires not only good understanding of the different power system components and their behaviors, but also a good knowledge and analysis of the anomalous circumstances and faults that can occur in any element of the electrical system. Furthermore, the rapid change and development of relay principles and their technologies are further factors that force people working in the industry to continually expand and update their knowledge. In this article we have tried to shed light on the evolution of protection relays from the advent of electricity to the present day. We also tried to predict future prospects and trends in this area.I. IntroductionThe protection relay is an integral part of any electrical power system. The fundamental goal of system protection is to quickly isolate a problem so that unaffected parts of a system can continue to function. Protection relays are the decision-making device in the protection scheme [1]. These relays have experienced, over the course of more than a century, a major change in their functionality and technologies. Each change brings with it advantages and improvements both from a technical and financial point of view. In this article, we have tried to shed light on the evolution of protection relays from the advent of electricity to the present day. We also tried to predict future prospects and trends in this area.II. Historical contextFrom the first days of the advent of electricity, the need for devices that allowed the avoidance of unwanted events in the power system was prescribed. The history of protective relays dates back more than... middle of paper ... ...NG, vol. 60, no. 5, 2009.[21] Internet forum: «Tips from RelaySpecialist experts», http://rza.communityhost.ru/.[22] V. Gurevich, "PROBLEMS WITH ASSESSING THE RELIABILITY OF RELAY PROTECTION", Электротехнические комплексы и SISTEMы управления, no. 3, pp. 56-59, 2010.[23] A. ABDELMOUMENE and H. BENTARZI, "Reliability Enhancement of Power TransformerProtection System", Journal of Basic and AppliedScientific Research (J. Basic. Appl. Sci. Res.,2(10)10534-10539, 2012).[24] USNRC, “Development of Quantitative Software Reliability Models for Nuclear Power Plant Digital Protection Systems,” U.S. Nuclear Regulatory Commission, Office of Nuclear Regulatory Research, 2011.25] IAEA, “Modern Instrumentation and Control for Power Plants nuclear power: a guide.", InternationalAtomic Energy. Agency, Vienna, 1999.