• Low (EFLPTOC)• High (EFHPTOC)• Instantaneous (EFIPTOC).EFLPTOC contains several types of time-delay characteristics. EFHPTOC andEFIPTOC are used for fast clearance of serious earth faults.5.2.2 Directional earth-fault protection DEFxPDEF5.2.2.1 IdentificationTable 62:Function identificationDifferent stages: Low stage High stageIEC 61850 identification: DEFLPDEF DEFHPDEFIEC 60617 identification: I0>-> I0>>->ANSI/IEEE C37.2 device number: 67N-1 67N-25.2.2.2 FunctionalityThe earth-fault function DEFxPDEF is used as directional earth-fault protection forfeeders.The function starts and operates when the residual current and residual voltage (-U0) exceed the set limits and the angle between them is inside the set operating sector.The operate time characteristic for low stage (DEFLPDEF) and high stage(DEFHPDEF) can be selected to be either definite time (DT) or inverse definiteminimum time (IDMT).In the DT mode, the function operates after a predefined operate time and resets whenthe fault current disappears. The IDMT mode provides current-dependent timercharacteristics.The function contains a blocking functionality. It is possible to block function outputs,timers or the function itself, if desired.5.2.2.3 Directional earth-fault principlesIn many cases it is difficult to achieve selective earth-fault protection based on themagnitude of residual current only. To obtain a selective earth-fault protectionscheme, it is necessary to take the phase angle of I0 into account. This is done bycomparing the phase angle of I0 to that of the residual voltage (-U0).Relay characteristic angleThe Characteristic angle, also known as Relay Characteristic Angle (RCA), RelayBase Angle or Maximum Torque Angle (MTA), is used in the "Phase angle" modeSection 5 1MRS756378 DProtection functions146 REF615Application Manual
