Under-voltage monitoring relay LINETRA ® VMD42 series

over-voltagefrequencyphase sequence

Overview
The LINETRAXX® VMD423 series are three-phase voltage and frequency monitoring relays designed to supervise the voltage and frequency at the grid feeding point for distributed generation systems (>30 kW). Measurements can be taken directly on low-voltage networks or via voltage transformers (100 V) at medium-voltage feed-in points. The device detects undervoltage/overvoltage, underfrequency/overfrequency, asymmetry, phase failure and phase sequence. An alarm relay operates within ≤ 80 ms when configured limit values are exceeded; overvoltage is evaluated as the average over a 10-minute interval. The VMD423 requires a separate supply; the VMD423H is supplied from the monitored system.

Certificates of non objection

• DIN V VDE V 0126-1-1:2006-02 (selected countries)
• EN 50438:2007 (where applicable)
• National approvals: C10/11 (Belgium), ENEL guideline references, others as listed

Features

• Versions: VMD423 with separate supply; VMD423H supply from monitored system
• Monitoring: undervoltage, overvoltage (10-min average), underfrequency, overfrequency in 3(N)AC systems (AC 0…500 V)
• Asymmetry, phase failure and phase sequence detection
• Adjustable start-up delay, response delay and delay on release; adjustable switching hysteresis
• r.m.s. value measurement (AC + DC) and multifunctional LC display
• Two independent alarm relays (changeover contacts); selectable N/C or N/O and fault memory behaviour
• LED indicators: Power On, Alarm 1, Alarm 2; internal test/reset button
• Password-protected settings; sealable transparent cover; continuous self-monitoring
• Push-wire or screw terminals depending on article number; two-module (36 mm) housing; RoHS compliant

Applications

• Monitoring of automatic switching points for private generation in parallel with the public low-voltage grid
• Grid-connection compliance according to DIN V VDE V 0126-1-1, EN 50438 and national guidelines
• Suitable for PV plants, CHPs, wind and hydro power plants and other distributed generation

Variants
Type | Supply voltage U_S* | Nominal system voltage U_n* | Response value | Art. No.*
VMD423-D-1 | DC 9.6…94 V / AC 16…72 V, 15…460 Hz | 3(N)AC 0…500 V, 40…65 Hz | AC 10…500 V | B73010020 / B93010020
VMD423-D-2 | DC 70…300 V / AC 70…300 V, 15…460 Hz | 3(N)AC 0…500 V, 40…65 Hz | AC 10…500 V | B73010021 / B93010021
VMD423H-D-3 | U_n (device supplied by measured system) | 3(N)AC 0…500 V, 40…65 Hz | AC 70…500 V | B73010022 / B93010022
(* Absolute values. B7… = push-wire terminal / B9… = screw-type terminal)

Optional accessories
Type | Art. No.
Mounting clip for screw mounting (one piece per device) | B98060008
Mounting frame XM420 | B990994

Downloads (selection)

• Declaration of conformity and certificates
• Datasheets, manuals and quick start guides
• Tender texts and UKCA/CE declarations

Technical specifications

• Measured quantities: three-phase voltages (r.m.s.), frequency, asymmetry, phase sequence, phase failure
• Voltage measurement range: AC 0…500 V (nominal system voltage)
• Frequency range: 40…65 Hz
• Overvoltage detection: average over 10-minute interval; relay activation ≤ 80 ms at limit values
• Outputs: two separate alarm relays (changeover contacts)
• User functions: adjustable delays and hysteresis; password protection; test/reset
• Indicators: LC display, LEDs; measured value memory
• Terminals: push-wire or screw-type; enclosure: 2-module 36 mm
• Compliance: RoHS and applicable national certifications