SEG MRN3-11D

Core Technical Specifications

• Rated Measuring Voltage: 3 × 100 V / 3 × 230 / 400 VAC
• Detection Functions: Overvoltage, Undervoltage, Overfrequency, Underfrequency, df/dt frequency change rate monitoring
• Output Relay Contacts: 5 groups of independent SPDT trip/output relays
• Communication Port: RS485 Modbus RTU
• Mounting Form: Standard 19-inch rack door mounting / panel flush mounting
• Overall Size: 280 mm × 140 mm × 80 mm
• Unit Weight: 1.8 kg
• Operating Temperature: -25 °C ~ +70 °C
• Trip Delay Range: 0.01 s ~ 999 s adjustable via front panel keypad

Function & Performance Features

1. All-in-one grid abnormality detection, replaces 4–6 separate single-function relays to reduce cabinet wiring space
2. Ultra-fast decoupling response when grid fault occurs, immediately sends trip signal to generator grid-connected circuit breaker
3. Digital LED display for real-time three-phase voltage, frequency and frequency gradient value
4. Front panel SELECT/SET keypad for full parameter configuration without auxiliary programming tool
5. Independent alarm and trip relay outputs, realize graded warning and emergency disconnection control
6. Fault event memory function, stores latest 50 groups of fault records with time stamp for post-failure analysis
7. Wide temperature range adaptation, suitable for outdoor generator container cabinet installation

Working Principle

1. Real-time sampling of three-phase grid voltage and frequency signals via internal voltage transformer
2. MCU core compares sampled data with user-set threshold parameters continuously
3. When voltage/frequency/frequency change rate exceeds set limit, internal timing circuit starts delay countdown
4. After delay time expires, drive corresponding output relay contact action to cut off generator grid connection switch
5. All fault data is stored in non-volatile memory, uploaded to upper monitoring system via RS485 bus

Material Composition & Structural Characteristics

• Outer Housing: ABS flame-retardant plastic front panel, cold-rolled metal rear shell with EMC shielding layer
• Display Unit: Red digital high-brightness LED display, dust-proof transparent protective window
• Control Core: Industrial anti-interference 32-bit microcontroller chip
• Signal Input Circuit: Isolated voltage sampling transformer to isolate generator high voltage and internal control circuit

Installation Requirements

1. Install on generator control cabinet door, front panel reserved observation and operation space
2. Voltage signal input wiring must use twisted shielded cable, separate from power cable wiring trough
3. Relay output control circuit needs to add external fuse protection to avoid contact burnout
4. Ground the rear shell shielding terminal to cabinet protective earth to resist field electromagnetic interference

Application Scenarios

• Distributed photovoltaic power station grid-connected protection
• Diesel generator set parallel to municipal power grid
• Cogeneration natural gas generator station safety decoupling
• Wind turbine auxiliary generator grid monitoring
• Industrial self-owned power plant off-grid fault protection

Usage Precautions

1. Re-calibrate voltage threshold parameters after grid voltage transformation ratio changes
2. Regularly export fault records every quarter to check hidden grid fluctuation risks
3. Do not install near high-current contactors and frequency converters to prevent signal sampling distortion
4. When replacing unit, keep wiring sequence consistent to avoid reverse voltage sampling damage internal transformers