5-106 F60 Feeder Management Relay GE Multilin5.5 GROUPED ELEMENTS 5 SETTINGS5The positive-sequence restraint must be considered when testing for pick-up accuracy and response time (multiple ofpickup). The operating quantity depends on the way the test currents are injected into the relay:• single-phase injection: I op = 1/3 × (1 – K) × I injected• three-phase pure zero- or negative-sequence injection, respectively: I op = Iinjected.• the directional unit uses the negative-sequence current and voltage for fault direction discriminationThe following table defines the Negative Sequence Directional Overcurrent element.The negative-sequence voltage must be higher than the PRODUCT SETUP ÖØ DISPLAY PROPERTIES ÖØ VOLTAGE CUT-OFFLEVEL value to be validated for use as a polarizing signal. If the polarizing signal is not validated neither forward nor reverseindication is given. The following figure explains the usage of the voltage polarized directional unit of the element.The figure below shows the phase angle comparator characteristics for a Phase A to ground fault, with settings of:ECA = 75° (Element Characteristic Angle = centerline of operating characteristic)FWD LA = 80° (Forward Limit Angle = ± the angular limit with the ECA for operation)REV LA = 80° (Reverse Limit Angle = ± the angular limit with the ECA for operation)The element incorporates a current reversal logic: if the reverse direction is indicated for at least 1.25 of a power systemcycle, the prospective forward indication will be delayed by 1.5 of a power system cycle. The element is designed to emu-late an electromechanical directional device. Larger operating and polarizing signals will result in faster directional discrimi-nation bringing more security to the element operation.Figure 5–54: NEG SEQ DIRECTIONAL CHARACTERISTICSThe forward-looking function is designed to be more secure as compared to the reverse-looking function, and therefore,should be used for the tripping direction. The reverse-looking function is designed to be faster as compared to the forward-looking function and should be used for the blocking direction. This allows for better protection coordination. The abovebias should be taken into account when using the Negative Sequence Directional Overcurrent element to ‘directionalize’other protection elements.OVERCURRENT UNIT DIRECTIONAL UNITMODE OPERATING CURRENT DIRECTION COMPARED PHASORSNegative-Sequence I op = |I_2| – K × I_1| Forward –V_2 + Z_offset × I_2 I_2 × 1∠ECAReverse –V_2 + Z_offset × I_2 –(I_2 × 1∠ECA)Zero-Sequence Iop = |I_0| – K × |I_1| Forward –V_2 + Z_offset × I_2 I_2 × 1∠ECAReverse –V_2 + Z_offset × I_2 –(I_2 × 1∠ECA)827806A2.CDRVAG (reference)VCG VBG–I_2 lineI_2 lineECA line–ECA lineLALALALA ECAFWD OperatingRegionREV OperatingRegionFWDLAFWDLAREVLAREVLAV_2 line–V_2 line
