Technologies used in Power System Protection Systems

The electromagnetic, electromechanical and solid state (analog electronic) technologies have been used in protection systems since the late 1800´s. The developments in VLSI circuits prompted the use of analog electronics in designing and building protective relays. Since the introduction of microprocessors, their use in protection systems has been increasing gradually. The modern protection systems use them along with the needed analog electronics. The technologies used in protection systems are described in this paper. Some of the changes in the designs that have become possible due to the versatility of the present technologies are discussed. Some thoughts on the expected direction in which power system protection is likely to move are identified.