20304050708090100Io / % of In0 90453015 7560-90 -45 -30 -15-75 -60Min forward angle1088 deg85 deg73 deg100% of In20% of In1% of InGUID-F9F1619D-E1B5-4650-A5CB-B62A7F6B0A90 V2 ENFigure 149: Phase angle 88 amplitude (Directional mode = Forward)4.2.2.9 ApplicationThe directional earth-fault protection DEFxPDEF is designed for protection andclearance of earth faults and for earth-fault protection of different equipmentconnected to the power systems, such as shunt capacitor banks or shunt reactors,and for backup earth-fault protection of power transformers.Many applications require several steps using different current start levels and timedelays. DEFxPDEF consists of two different stages.• Low DEFLPDEF• High DEFHPDEFDEFLPDEF contains several types of time delay characteristics. DEFHPDEF isused for fast clearance of serious earth faults.The protection can be based on the phase angle criterion with extended operatingsector. It can also be based on measuring either the reactive part Iosin(φ) or theactive part Iocos(φ) of the residual current. In isolated networks or in networkswith high impedance earthing, the phase-to-earth fault current is significantlysmaller than the short-circuit currents. In addition, the magnitude of the faultcurrent is almost independent of the fault location in the network.The function uses the residual current components Iocos(φ) or Iosin(φ) accordingto the earthing method, where φ is the angle between the residual current and thereference residual voltage (-Uo). In compensated networks, the phase anglecriterion with extended operating sector can also be used. When the relaycharacteristic angle RCA is 0 degrees, the negative quadrant of the operation sectorcan be extended with the Min forward angle setting. The operation sector can beset between 0 and -180 degrees, so that the total operation sector is from +90 to-180 degrees. In other words, the sector can be up to 270 degrees wide. This allows1YHT530004D05 D Section 4Protection functions615 series 295Technical Manual
