MRI1 - Digital multifunctional relay for time overcurrent protection

The MRl1 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 MRI1 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 MRI1 can be employed as a back-up protection for distance and differential protective relays. A similar, but simplified version of overcurrent relay IRI1 with limited functions without display and serial interface is also available.

FEATURES & FUNCTIONALITY

The MRl1 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 MRI1 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 MRI1 can be employed as a back-up protection for distance and differential protective relays. A similar, but simplified version of overcurrent relay IRI1 with limited functions without display and serial interface is also available.