Description
Woodward MRU311DM
Technical Specifications:
- Brand: Woodward
- Model: MRU311DM
- Product Type: Digital Three-Phase Voltage Protection Relay (ANSI 27/59/47)
- Measured Voltage Range: 0–690 VAC (Adaptable to 100/230/400/690V systems)
- Frequency Range: 40–70 Hz (Auto-adaptive to 50/60Hz systems)
- Auxiliary Power Supply: 24VDC or 85–265V AC/DC wide-range power input
- Measurement Accuracy: ≤ ±1% of rated voltage
- Certifications: CE, UL, RoHS compliant
Functional Features:
- Overvoltage and Undervoltage Protection: Features two-stage adjustable thresholds with independent time delays (0.1–10s) for precise fault isolation.
- Phase Unbalance and Sequence Protection: Continuously monitors phase unbalance (5–20% adjustable) and detects phase sequence errors or phase loss to prevent motor reversal or burnout.
- Symmetrical Component Monitoring: Real-time calculation of positive, negative, and zero-sequence voltages (U1/U2/U0) for sensitive detection of ground faults and asymmetrical faults.
- Dual Parameter Groups: Stores two independent parameter sets to seamlessly adapt to different operating conditions or grid switching scenarios.
- Digital Filtering: Utilizes Discrete Fourier Transform (DFT) digital filtering to effectively suppress harmonics and DC components, ensuring strong anti-interference capabilities.
Application Scenarios:
Extensively applied in generator sets, power transformers, industrial medium-voltage switchgear, and industrial power grid voltage monitoring and protection systems.
Performance Parameters:
- Relay Outputs: 1× SPDT trip relay (5A/250VAC) and 2× independent alarm/trip digital outputs.
- Analog Output: 4–20mA analog signal for continuous voltage monitoring and transmission.
- Communication Interface: RS485 port supporting Modbus RTU protocol for seamless integration with SCADA and DCS systems.
Material Composition:
Housed in a robust, flame-retardant industrial plastic enclosure with high-quality gold-plated internal relays and multi-layer industrial-grade PCBs for superior electrical conductivity and thermal dissipation.
Structural Characteristics:
Features a compact DIN-rail or panel-mount design with dimensions of 108×70×115 mm and a weight of approximately 0.4 kg. The front panel includes an intuitive LCD display and navigation push-buttons for easy parameter configuration and status monitoring.
Working Principle:
The relay continuously samples three-phase voltage signals and processes them using advanced microprocessor algorithms. It calculates the fundamental frequency components via DFT filtering, compares the values against user-defined thresholds and time delays, and triggers the corresponding output relays when a fault condition is confirmed.
Installation Requirements:
Mount securely on a standard DIN rail or panel. Connect voltage inputs and auxiliary power strictly according to the wiring diagram. Ensure proper system grounding and maintain adequate clearance from high-frequency interference sources.
Usage Precautions:
Always disconnect auxiliary power before wiring. After a fault trip, the relay can be reset manually via the front panel button, electrically via the reset input terminal, or via software command. Never attempt to clear the fault memory while the fault condition still exists.
