Voltage and
Frequency Relay


The MRU4 is a protection relay which uses the latest Dual-Core-Processor Technology to provide precise and reliable protective functions and is very easy to operate. It is designed to protect electrical equipment from dangerous voltage fluctuations. For example protection against under voltages caused by mains shortcircuits, or overvoltages due to load shedding or failure of a generator voltage controller. Its compact design makes the MRU4 ideal for installation within the LV terminal compartments of compact SF6-insulated MV systems.

All inclusive:
All protection features inclusive
• Parameter setting software
• Disturbance analysis software

Comprehensive frequency protection package
Each of the six elements can be used as:
• f< or f> (over- and underfrequency supervision)
• df/dt (ROCOF)
• Rate of change of frequency
• (f< and df/dt) or (f> and df/dt) Combination of over-, under- and rate of change of frequency (ROCOF)
• (f< and DF/DT) or (f> and DF/DT) Combination of over-, under- and increase of frequency
• Delta Phi (Vector surge)

power quality
THD protection

SIX Elements voltage protection
• Under- and overvoltage Programmable time dependent
• undervoltage tripping characteristic

Flexible Fourth Voltage measuring input
• 2 elements VE> or VX (for Synch Check)

Synch Check
• Generator-to-System, System-to-System
• Options to switch onto dead bus bars

Two Elements residual voltage protection
• VE >

Six Elements voltage asymmetry supervision
• Under- and overvoltage in positive phase sequence system, overvoltage in negative phase sequence system

• Adjustable LVRT-profiles
• Optionally AR-controlled

Additional highlights
• Plausibility checks
• Status display
• Comprehensive measured valuesand statistics
• Masking of unused functions
• Multi-Password-Leve

Sliding-mean-square supervision
• Adjustable (VDE-AR 4105)

• Disturbance recorder: 120 s non volatile
• Fault recorder: 20 faults
• Event recorder: 300 events
• Trend recorder: 4000 non volatile entries

PC Tools
• Setting and analyzing software
• Including page editor to design own pages

Commissioning support
• USB connection
• Customizable Display (Single-Line, ...)
• Customizable Inserts
• Copy and compare parameter sets
• Configuration files are convertible
• Forcing and disarming of output relays
• Fault simulator: current and voltage
• Graphical display of tripping characteristics
• 7 languages selectable within the relay

Communication options
• IEC61850
• Profibus DP
• Modbus RTU or Modbus TCP
• IEC60870-5-103
• DNP 3.0 (RTU, TCP, UDP)

• One Breaker
• Breaker wear

• Up to 80 logic equations for protection, control and monitoring

Time synchronisation