Operation logic proposed for time overcurrent relays

This paper presents a new logic of operation for time overcurrent relays. With the application of the proposed technique, the sensitivity of time overcurrent relays is increased. In order to obtain this, the relay operates with a dynamic pickup setting, such as load current. Additionally, fast operation of overcurrent relays is obtained. The functional structure is described and the logic of overcurrent relay is evaluated under different operative states. We describe the functional structure of the proposed relay and its implementation in laboratory tests. Index Terms--Overcurrent relay, pickup current, sensitivity.