Digital Overcurrent Relays in Industrial networks Advanced fetures for optimization of tripping times

This paper focuses on the possible use of additional features of the modern digital protective relays in medium voltage industrial distribution systems to reduce the tripping times and enhance the selectivity of the protection system. One of these additional features is the directional comparison. The paper describes the possible use of this function on a simplified real-world model of an industrial distribution system and compares the resulting tripping times with a conventional approach using only nondirectional and directional time-independent overcurrent protections. The reduction of tripping times is especially important in context of the continuous increase of short circuit power levels in the system. We can observe these phenomena in many industrial networks, due to upgrades in high voltage distribution networks powering the industrial networks, but also due to installation of new local electricity resources in the industrial networks. Reducing the tripping time reduces the risk of damage to the power equipment due to short circuit current, increases the reliability and lifetime of network equipment.