BENDER VMD422-D-2 Voltage and Frequency Monitoring Relay

Product Detailed Description

• Function:

• Voltage Monitoring: Continuously monitors for undervoltage (

• Frequency Monitoring: Monitors for underfrequency (

• Asymmetry Monitoring: Can detect phase asymmetry (unbalance) in the three-phase system.

• Phase Failure and Phase Sequence Monitoring: Identifies if a phase is lost or if the phase sequence is incorrect.

• Alarm Relays: Equipped with two separate alarm relays (each with one changeover contact, NO/NC selectable) that activate when a monitored parameter exceeds or falls below its set threshold.

• Adjustable Delays: Features adjustable start-up delay, response delay, and delay on release to prevent nuisance tripping from transient fluctuations or during system startup.

• Features:

• Digital Measured Value Display: An integrated multi-functional LCD provides continuous display of the currently measured voltage and/or frequency values.

• LED Indicators: LEDs for "Power On", "Alarm 1", and "Alarm 2" provide quick visual status.

• Measured Value Memory: Stores the measured value that triggered the alarm relay, aiding in fault analysis.

• Cyclical Self-Monitoring: Ensures the relay itself is functioning correctly.

• Internal Test/Reset Button: Allows for local testing and resetting of alarms.

• Password Protection: Device settings can be password protected to prevent unauthorized changes.

• Sealable Transparent Cover: Protects the settings and display from tampering and environmental factors.

• Compact Design: Typically a two-module enclosure (36 mm wide) for DIN rail mounting, saving space in control cabinets.

• Terminal Type: The "-D-2" typically refers to the variant with AC/DC 70…300 V supply voltage and can come with either screw-type or push-wire terminals (e.g., B73010011 for push-wire, B93010011 for screw-type for 400/230V systems).

Product Parameters

For the BENDER VMD422-D-2 (specifically for 3(N)AC 400/230 V systems, 40-65 Hz):

• Nominal System Voltage (Un): 3(N)AC 400 V / 230 V (40 - 65 Hz)

• Measurement Range: 0...500 V (for monitoring)

• Supply Voltage (Us): AC/DC 70...300 V, 15...460 Hz (separate supply voltage is required for VMD422, unlike VMD422H which is system-supplied).

• Monitoring Functions (Configurable):

• Undervoltage (

• Overvoltage (>U1, >U2): e.g., AC 423-460 V / 244-264 V (phase-to-phase / phase-to-neutral)

• Underfrequency (

• Overfrequency (>f): e.g., 50.2 - 52.0 Hz

• Asymmetry (Asymmetry): 5...30%

• Phase failure and phase sequence monitoring.

• Response Values (according to VDEW guideline “Generator at the public low-voltage grid”): Alarm relay activates within 180 ms if voltage/frequency exceed thresholds.

• Hysteresis (Voltage/Frequency): Adjustable / Permanently set (e.g., 0.1 Hz for frequency)

• Time Delays:

• Start-up delay (t_start): 0 - 300 s (default 30 s)

• Response delay (t_on): 0 - 300 s

• Delay on release (t_off): 0 - 300 s

• Alarm Relays: 2 changeover contacts (SPDT), electrically isolated.

• Contact Rating: e.g., AC 230 V, 5 A (resistive load).

• Degree of Protection: IP20 (terminals), IP40 (enclosure) - typically.

• Operating Temperature: -25 °C to +55 °C.

• Mounting: DIN rail (35 mm).

• Dimensions: Typically 36 mm (2 modules) width.

• Compliance: RoHS compliant, meets relevant EN/IEC standards (e.g., EN 60255-27, EN 61010-1).

Product Advantages

• Comprehensive Protection: Monitors multiple critical grid parameters (voltage, frequency, asymmetry, phase sequence/failure) providing robust protection for connected equipment.

• High Reliability & Precision: True RMS measurement and fast response times ensure accurate and timely detection of grid disturbances.

• Safety Compliance: Designed to meet relevant safety standards, crucial for grid connection points of power generating systems (e.g., according to VDEW guideline).

• Flexible Operation: Two independent alarm relays, adjustable settings, and selectable operating modes (N/C or N/O operation, fault memory) allow for high adaptability to various applications.

• User-Friendly Interface: Digital LCD display, LEDs, and intuitive setting options simplify configuration and status monitoring.

• Robust & Compact Design: Suitable for industrial environments, and its small form factor saves panel space.

• Reduced Maintenance: Push-wire terminals (if equipped) offer high contact stability and are largely maintenance-free compared to traditional screw terminals, especially under vibration.

Precautions

• Correct Wiring: Strictly adhere to the wiring diagram provided in the Bender manual. Ensure correct connection of the monitored system voltage (L1, L2, L3, N) and the separate supply voltage (A1, A2). Improper wiring can damage the device or lead to incorrect readings/trips.

• System Compatibility: Ensure the relay's nominal system voltage and frequency ranges match your application's power grid.

• Supply Voltage: For the VMD422-D-2, a separate supply voltage (AC/DC 70-300V) is mandatory. Do not attempt to supply it from the monitored system voltage if it's outside this range or if the specific VMD422-D-2 variant requires an external supply.

• Parameter Settings: Carefully configure all thresholds (undervoltage, overvoltage, underfrequency, overfrequency, asymmetry) and time delays according to the specific requirements of the connected equipment and relevant grid codes/standards. Incorrect settings can lead to false alarms or inadequate protection.

• Environmental Conditions: Install the device within its specified operating temperature and humidity range. Protect it from excessive vibration, direct sunlight, and corrosive atmospheres.

• Security: Utilize the password protection feature to prevent unauthorized changes to critical settings.

• Testing: Perform functional tests after installation and commissioning to verify correct operation of the monitoring functions and alarm relays.

Product Applications

The BENDER VMD422-D-2 is primarily used in applications where reliable monitoring of three-phase voltage and frequency is critical for safety, equipment protection, and grid compliance.

• Grid Connection of Power Generating Systems: Essential for monitoring the transfer connection point of photovoltaic (PV) systems, wind turbines, combined heat and power (CHP) plants, and other distributed generation systems to ensure compliance with grid connection rules (e.g., VDEW guideline for generators at the public low-voltage grid). It helps ensure disconnection from the grid during abnormal voltage or frequency events.

• Protection of Voltage-Sensitive Machines and Electrical Installations: Safeguarding industrial machinery, motors, pumps, and other equipment from damage due to voltage sags, swells, or frequency deviations.

• Monitoring of Stand-by and Emergency Supply Systems: Supervising the stability and availability of backup power sources, such as generators or UPS systems.

• Switching Operations: Used to enable or disable machinery or parts of an electrical system based on specific voltage or frequency levels.

• Transformer Protection: Monitoring voltage conditions to protect transformers from over or undervoltage.

• Protection of Three-Phase Motors: Protecting motors against phase failure, phase open-circuit, and incorrect phase sequence.

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