CONDITION : USED BUT TESTED AND WORKING FINE

Key Features & Specifications

1. Model & Revision

   • Part Number: MRU4A0AB

   • Revision: Y (latest hardware/software updates)

   • Series: High ProTec (Woodward’s protection relay line)

2. Primary Protection Functions

   • Over/Under Voltage (59/27):

     • Adjustable thresholds (e.g., 110%–130% for overvoltage, 70%–90% for undervoltage).

   • Over/Under Frequency (81O/81U):

     • Typical range: 40–70 Hz (configurable).

   • Phase Imbalance (47):

     • Detects voltage unbalance (>5% adjustable).

   • Neutral Displacement (59N):

     • For ground fault detection in ungrounded systems.

3. Inputs & Outputs

   • Voltage Inputs:

     • 3-phase + neutral (57–300V AC line-to-line, via PTs).

   • Binary Inputs: 4–8 configurable status inputs (e.g., breaker position).

   • Relay Outputs: 6–10 changeover contacts (trip, alarm, load shedding).

   • Communication:

     • RS-485 (Modbus RTU) or optional Ethernet (IEC 61850).

4. Settings & Programmability

   • Flexible Logic: User-defined trip/alarm conditions via Woodward’s ProTec Plus software.

   • LED Indicators: Real-time status (faults, active protections).

   • Event Logging: Stores 100+ fault records with timestamps.

5. Environmental & Certifications

   • Operating Temp: -40°C to +70°C (-40°F to +158°F).

   • Standards: IEEE C37.90 (EMC), IEC 60255 (protection relays).

Typical Applications

• Power Generation: Generator protection (overvoltage due to AVR failure).

• Industrial Plants: Motor/pump protection from voltage sags/swells.

• Renewables: Grid-tied solar/wind farm voltage stability.

Wiring & Installation

1. Voltage Inputs:

   • Connect to potential transformers (PTs) for high-voltage scaling.

2. Trip Outputs:

   • Wire to circuit breaker coils or alarm panels.

3. Communication:

   • RS-485 for SCADA integration (Modbus address must match).

Configuration Steps

1. Set Thresholds:

   • Overvoltage: 110% of nominal (e.g., 121V for 110V system).

   • Undervoltage: 85% of nominal (e.g., 93.5V for 110V system).

2. Time Delays:

   • Adjust trip delays (0.1–300 sec) to avoid nuisance tripping.

3. Test Mode:

   • Simulate faults using secondary injection (verify relay response).