Directional Earth Fault Relay is used to protect the transformer/generator/alternator from over current fault. The relay sense the fault current in only one direction, the relay does not operate when the current in opposite direction. Electromechanical relays (EM) sense of directionality is accomplished by voltage. Directional relays are incorporated in the power systems sector in the field of electrical engineering to enhance the stability and reliability of electricity grids. This post is meant to focus on the condition of operation of the aforementioned handling device, breaking down all its operational. In this technical guide we will walk you through everything you need to know about directional and non-directional relays, their working principles, applications, and how they function within substation protection schemes.
[PDF Version]