Lovato PMVF52 Interface Protection Relay, CEI 0-21

Lovato PMVF52 interface protection relay, voltage and frequency

The Lovato PMVF52 is an interface protection system unit built to the Italian CEI 0-21 standard, used to disconnect a generator or inverter-based source from the low-voltage grid when voltage or frequency leaves the permitted limits. It monitors three-phase systems with or without neutral and single-phase systems, with dual thresholds for minimum and maximum voltage and frequency. Seven Star LLC supplies the PMVF52 in Oman and the GCC as an independent supplier in Muscat.

The relay is mostly known in photovoltaic and cogeneration plants. In the Gulf it is used where project specifications or the grid operator refer to interface protection, and the exact settings must always come from the local utility requirement; the CEI 0-21 name only describes the characteristics the device was designed to.

PMVF52 technical specifications

How interface protection works

When a plant is connected in parallel with the grid, it must not keep feeding a network that has been de-energised or has drifted outside normal limits. The relay watches the grid-side voltage and frequency, compares each against two sets of thresholds and, when a limit is exceeded for longer than its time setting, it trips its output relays that open the interface device. Two thresholds, a fast one for severe deviations and a slower one for moderate ones, are what the dual-threshold phrase means.

The supply is wide-range and works from 24 to 240 V in AC or DC, so the relay can be powered from a battery or UPS and keep working through a grid outage, which is essential for the protection function. The five dry-contact inputs allow external signals such as remote enable, interface-device feedback or test commands to be connected.

Where the PMVF52 fits in the system

The PMVF52 sits in the interface panel between the generator or inverter system and the point of common coupling. Its two changeover outputs trip the interface contactor or breaker, and the third NO output can signal an alarm. Related Lovato products include the PMVF30, PMVF71, PMVF81 and PMVF90 voltage and frequency monitors, and the PMVFUPS01 and PMVFUPS02 units for UPS applications, which are different families with different thresholds, so check the application against each data sheet.

PMVF52 selection and ordering checklist

• Confirm the utility requires interface protection and obtain its voltage, frequency and time settings
• Check the system: three-phase with or without neutral, or single-phase
• Check the 400 V L-L / 230 V L-N 50 Hz rating of the grid
• Provide a UPS or battery auxiliary supply within 24 to 240 V
• Count inputs and outputs needed for the interface device
• Check the cabinet space: 4 modules

Installation, commissioning and maintenance of the PMVF52

Wire the measuring inputs through fuses from the grid side of the interface device, connect the auxiliary supply, and wire output relays to the shunt trip or contactor coil. At commissioning, enter the utility-approved thresholds and times and perform a test: simulate or inject over/under voltage and frequency and check the interface device opens. Document the test results because the utility will ask for them. Periodically repeat the functional test, and keep the setting record with the panel drawings.

Typical PMVF52 applications in Oman and the GCC

Rooftop and ground-mounted solar plants, battery storage, gas engine cogeneration and standby generators with parallel operation need grid-side protection. As solar capacity grows across Oman and neighbouring states, interface protection relays are a routine part of the connection package. Always check the specific utility requirement, because local grid codes may specify limits that differ from the Italian standard.

Testing and documenting the PMVF52 settings

Interface protection is a safety function, so the commissioning record matters as much as the hardware. Keep a table of every threshold and time delay entered, the date, the person who tested and the injected test values. When the plant is sold, expanded or re-certified, that record shows that the relay still matches the utility conditions.

Pay attention to the auxiliary supply. The relay accepts AC or DC from 24 to 240 V, which means a 24 V DC battery supply can keep it alive when the grid is lost. Do not feed it from the same supply that the inverter or generator provides, since that source disappears exactly when protection is needed. The five dry-contact inputs are available for external signals, and the function assigned to each should be taken from the instruction manual before wiring.

Information to send with an RFQ for the PMVF52

• Part number PMVF52 and quantity
• System type, voltage and frequency
• Utility or project specification references
• Auxiliary supply available
• Number of external inputs needed
• Delivery location

Documents and quotation

Send the part number PMVF52 and we will confirm the documents available for it, such as the technical data sheet, wiring diagram and instruction sheet, together with availability and lead time.

Seven Star LLC is an independent supplier in Muscat and is not an official channel of the manufacturer. Share the quantity, delivery location and project reference with the request and we will answer with a formal quotation.