MRI3 – Digital multifunctional relay for overcurrent protection

The MRl3 digital multifunctional relay is a universal time overcurrent and earth fault protection device intended for use in medium-voltage systems, either with an isolated/compensated neutral point or for networks with a solidly earthed/resistance-earthed neutral point. The protective functions of MRI3 which are implemented in only one device are summarized as follows:  Independent (Definite) time overcurrent relay,  inverse time overcurrent relay with selectable characteristics,  integrated determination of fault direction for application to doubly infeeded lines or meshed systems,  two-element (low and high set) earth fault protection with definite or inverse time characteristics,  integrated determination of earth fault direction for application to power system networks with isolated or arc suppressing coil (Peterson coil) neutral earthing. (ER/XR-relay type),  integrated determination of earth short-circuit fault direction in systems with solidly-earthed neutral point or in resistance-earthed systems (SR-relay type). Furthermore, the relay MRI3 can be employed as a back-up protection for distance and differential protective relays. A similar, but simplified version of overcurrent relay IRI1 with reduced functions without display and serial interface is also available.

FEATURES & FUNCTIONALITY

The MRl3 digital multifunctional relay is a universal time overcurrent and earth fault protection device intended for use in medium-voltage systems, either with an isolated/compensated neutral point or for networks with a solidly earthed/resistance-earthed neutral point. The protective functions of MRI3 which are implemented in only one device are summarized as follows:  Independent (Definite) time overcurrent relay,  inverse time overcurrent relay with selectable characteristics,  integrated determination of fault direction for application to doubly infeeded lines or meshed systems,  two-element (low and high set) earth fault protection with definite or inverse time characteristics,  integrated determination of earth fault direction for application to power system networks with isolated or arc suppressing coil (Peterson coil) neutral earthing. (ER/XR-relay type),  integrated determination of earth short-circuit fault direction in systems with solidly-earthed neutral point or in resistance-earthed systems (SR-relay type). Furthermore, the relay MRI3 can be employed as a back-up protection for distance and differential protective relays. A similar, but simplified version of overcurrent relay IRI1 with reduced functions without display and serial interface is also available.