Protector Trip Relays - Crompton Instruments

Phase Balance, Sequence andVoltage MonitorThe phase balance, sequence and voltage protector trip relay, isdesigned to monitor a three-phase supply for phase imbalance,low or missing phases or incorrect phase sequence and to trip arelay if it detects any anomaly. Two versions are available to suiteither three-phase three-wire (PSF/G3) or three-phase four-wire(PSF/G4) systems.Basic Parameters• Available with three voltage ranges 100-120V, 173-240V and 380-480V (Un)• Adjustable nominal voltage range• Adjustable trip delay 0.5-10s• Adjustable low voltage trip level 50-85%• Adjustable phase imbalance trip level 5-15%• Power on LED (green)• Fixed differential (hysteresis) 1%Part no. 3-phase 3-wire 3-phase 4-wire ProtectionPSF/G3 x Phase sequence, phase balance andunder voltagePSF/G4 x Phase sequence, phase balance andunder voltageOperationRotating machines are particularly vulnerable to incorrect phase sequence, androtate in the wrong direction, potentially leading to physical damage or the risk ofinjury to personnel. If one phase is lost because of a blown fuse, electric motors cancontinue to operate (single-phasing) which can result in severe electrical ormechanical damage.The PSF protector continuously monitors the three-phase supply, with all correctphase sequence applied and all three voltages balanced within the required limitsthe front panel, the LED will be off and the relay energised. An incorrect sequence,missing phase, out of balance or under voltage condition will de-energise the relayand the LED will illuminate. The set point control allows adjustment of the voltageimbalance, if one phase voltage differs from the other by more than the setpercentage, between 5% and 15%, than the relay will de-energise and the LED willilluminate. The time delay function operates only for the voltage imbalancecondition. This delay can be used to prevent nuisance tripping due to short termimbalance situations.Characteristics16