MRI3

Productomschrijving

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
• Digital filtering of the measured values by using discrete Fourier analysis to suppress the high frequency harmonics and DC components induced by faults or system operations,
• two parameter sets,
• selectable protective functions between:
– definite time overcurrent relay and
– inverse time overcurrent relay,
• selectable inverse time characteristics according to IEC 255-4:
– Normal Inverse (Type A)
– Very Inverse (Type B)
– Extremely Inverse (Type C)
– Special characteristics,
• reset setting for inverse time characteristics selectable,
• high set overcurrent unit with instantaneous or de-finite time function,
• two-element (low and high set) overcurrent relay both for phase and earth faults,
• directional feature for application to the doubly in-feeded lines or meshed systems,
• earth fault directional feature selectable for either isolated or compensated networks,
• sensitive earth fault current measuring with or without directional feature (X and XR-relay type),
• determination of earth short-circuit fault direction for systems with solidly-earthed or resistance-earthed neutral point,
• numerical display of setting values, actual measured values and their active, reactive components, memorized fault data, etc.,
• display of measuring values as primary quantities,
• withdrawable modules with automatic short circuiters of C.T. inputs when modules are withdrawn,
• blocking e.g. of high set element (e.g. for selective fault detection through minor overcurrent protection units after unsuccessful AR),
• relay characteristic angle for phase current directional feature selectable,
• circuit breaker failure protection,
• storage of trip values and switching-off time (tCBFP) of 5 fault occurrences (fail-safe of voltage),
• recording of up to eight fault occurrences with time stamp,
• free assignment of output relays
• serial data exchange via RS485 interface possible; alternatively with SEG RS485 Pro-Open Data Protocol or Modbus Protocol,
• suppression of indication after an activation (LED flash),
• display of date and time