Voltage Relays, Frequency Relays With Under And Over Frequency Protection, Manufacturer, Supplier, Exporter, Proton Power Control, Pune, Maharashtra, India

Voltage Frequency Monitoring Relay

Protection of 3 Phase devices against Over voltage, Under voltage,(UB) Single Phasing,(SPP) Over Frequency, Under Frequency, Reverse Phasing & Unbalance supply are one of the major issues in electrical systems. For safe running of 3-phase devices, special protections that keep a continuous watch on supply conditions are very essential. The major cause of maximum load burn-out is overloading,which occurs due to Unbalance Supply, Single Phasing or Reverse phasing conditions. VFR3P detects such conditions & protects the load from the burn out. 'Proton's VFR 3P' offers above protections along with 3 digit display showing R-Y,Y-B,B-R, voltages in scanning mode with precise accuracy.
Low/High voltage tripping to ensures trouble free running of 3-phase Loads, and also protection is provided against Over /Under Frequency

  • Supply Voltage: 3 Phase 415 VAC, 50 Hz (R, Y, B &N) (No auxiliary supply)
  • Output Contacts: Two changeover ( C-NO),Rating 5A at 230VAC
  • Voltage trip setting : Lower Limit is 340 for Under voltage (Resolution of 1 Volt) : Upper Limit is 460 Volts for OV (resolution of 1 V) ( Hysterisis between cut off & cut in is 10V)
  • Trip Time delay: Trip time Less than 100msec.for SPP, Reverse Phasing & Over Voltage Trip Time is settable for Under Voltage & Unbalance..
  • ON Delay: Selectable by keys from 1 to 60 sec.
  • Reset Mode: Auto reset.
  • Indications:
    1) SPP : RED LED
  • Keys:
    1) [ SET ] FUNCTION key, To select a set point function.
    2) [ /\ ] INC key, To increment set point.
    3) [ \/ ] DEC key, To Decrement set point.
  • Operating Temperature range:5 degree C to 60 degree C.
  • Relative Humidity:10 to 95%
  • Mounting:Din rail : Base mounting dimensions 55 (W) x 65 (L) x 125 (D) mm.


  • Micro controller based technology.
  • Voltage protection along with digital voltage readout.
  • Wide range of supply variation.
  • Unit will also works on any one phase is present.
  • Protection against Under Voltage.
  • Protection against Over Voltage.
  • Single Phasing & Reverse Phasing protection. Control output
  • All the set points settable by keys.
  • Phase unbalance protection.
  • Trip Delay for Under voltage & Unbalance is settable
  • Reverse Phasing Protection can be able to bypass through settings.
  • Indications for Low Voltage , High Voltage, SPP & Relay ON .
  • Message Display for SPP, Reverse Phasing & Unbalance Faults.
  • No separate auxiliary supply required.
  • Hold feature:- Press INC key in Running condition to observe particular supply voltage

1) If the input supply is within the range of the fault limit limits then On Timer starts decrementing on display & after set on Time over Relay will de ON with RLY indication glowing
2)If OV , UV, OF, UF, SPP/ reverse phasing / Unbalance occurs in the supply then relay will be OFF after the trip delay of that particular fault & LED starts blinking
3) If any phase to Voltage increases above OV set point belay will trip after trip delay (100)ms ) over .If that particular phase to phase voltage reduces below COV set point Relay will be on after the set rest delay is over
4) If any Phase to Phase Voltage increases / reduces above / the UB set point compared to other two Phase to Phase voltages , Relay will trip after delay over If that particular phase to phase voltage reduces / increases below / above (UB set point -/+ 10-V ) relay will be ON after the set reset delay over If the frequency reduces below UF or increases above OF then the relay will trip . Hysteresis is 1H2
5)If any of the Phase fails , Relay will trip after trip delay (100ms) over If all phases are present , relay will be ON after the set reset delay is over
6) If Phase sequence is changed to R-B-Y/Y-R-B/B-R-Y; Relay will trip after the trip delay (100 ms) over . if phase sequence is corrected to R-Y-B, relay will after the delay over UB /SPP/REVP,UV,UF, OF.

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