Woodward MRU4 A0AA Voltage Frequency Protection Relay
I. Product Brief Description
It belongs to the Woodward HighPROTEC series of high-precision voltage protection measurement and control devices. It features a dual-core processor architecture, focusing on the full-process monitoring and protection of three-phase voltage, frequency, phase sequence, and zero-sequence voltage. It can handle fault tripping and locking for grid overvoltage, undervoltage, abnormal frequency, three-phase imbalance, and islanding disconnection, etc. A0AA is the basic standard version hardware configuration. The cabinet is installed in an embedded manner, suitable for voltage safety protection scenarios of medium-voltage switch cabinets and generator set plant power supply systems.
Key Technical Parameters Table
Parameter Item Technical Indicators
Voltage measurement acquisition range 0 – 800V AC, three-phase four-wire / three-phase three-wire universal connection
Rated compatible voltage 100V, 110V, 230V, 400V, 690V systems can be set by software
Frequency measurement range 10 – 100Hz, compatible with 50Hz/60Hz power grid system
Digital input channels 8 channels of passive switch quantity input
Relay output contacts 6 passive trip / alarm relay contacts
Contact load capacity 250VAC 5A; 30VDC 8A
Power supply for operation DC 24~250V / AC 85~265V universal AC/DC power supply
Overall power consumption ≤ 12VA
Voltage protection setting accuracy ≤ ±0.5%FS
Frequency protection setting accuracy ≤ ±0.01Hz
Action delay range 0.01s~300s adjustable continuously
Operating temperature range -25℃ ~ +70℃
Storage and transportation temperature range -40℃ ~ +85℃
Protection grade IP52 (front operation panel), IP20 (inside cabinet)
Compliance standards IEC 60255, EN 61000 electromagnetic compatibility, UL certification, VDE grid specifications
Supporting debugging software Smart View dedicated parameter configuration, fault recording analysis software
Core product performance
Integrated complete set of ANSI standard voltage protection logic: overvoltage, undervoltage, zero-sequence overvoltage, excessive/insufficient frequency, three-phase voltage imbalance, phase sequence error, loss of voltage island protection, low-frequency load shedding, low voltage ride-through (LVRT) function;
Built-in fault recording, event sequence recording, disturbance recall functions, capable of storing thousands of grid abnormal events, facilitating fault traceability and troubleshooting;
Equipped with LCD display panel + physical operation buttons, local real-time viewing of three-phase voltage, frequency, phase difference, zero-sequence voltage operation data, local modification of protection settings;
Equipped with programmable logic unit, capable of customizing linkage tripping, alarm locking logic, suitable for islanding prevention requirements at self-owned power plants connection points;
Hardware full-channel self-check, automatic alarm output for power supply abnormalities, collection circuit disconnection;
Compact body design, can be directly installed in the low-voltage compartment of medium-voltage SF6 switch cabinets, with strong space adaptability;
Supports IRIG-B time synchronization (optional configuration), unified time synchronization for all protection devices in the station.
Application fields
Steam turbine, water turbine, gas turbine generator set terminal voltage monitoring and protection;
Factory self-owned power plants, distributed photovoltaic power station grid connection side island prevention, voltage and frequency safety control;
Medium-voltage switch cabinets, ring network cabinet bus voltage monitoring and fault trip protection;
Ship power station, mobile vehicle power station power quality monitoring and protection;
Data center, metallurgical and chemical enterprises plant power system voltage abnormality protection;
Low-frequency load shedding, voltage sag mitigation supporting measurement and control for distribution network lines.
List of mainstream models in the HighPROTEC series
MRU4: Voltage and frequency dedicated protection relay (this model),主打 voltage， zero-sequence， frequency comprehensive protection
MRA4： Current overload， short circuit， grounding fault current protection relay device
MRD4： Differential protection relay， dedicated for transformer， generator winding differential protection
MRS4： Synchronization connection + voltage comprehensive measurement and control device，兼具 synchronous check， voltage monitoring dual functions
MRF4： Feeder comprehensive protection device， integrated protection for overcurrent， zero-sequence， voltage for distribution network lines
MRP4： Specialized for motor protection， protection for large-power motor overload， overcurrent， phase failure
Suffix derivatives of the same model differences
A0AA： Basic model， no communication， embedded cabinet door installation， standard I/O
A0BB： Standard RS485 Modbus RTU communication version
A0CC： High-end version with Ethernet Modbus TCP/IEC61850 communication
B series： 19-inch standard rack embedded installation style
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