5-128 D30 Line Distance Relay GE Multilin5.5 GROUPED ELEMENTS 5 SETTINGS5The above bias should be taken into account when using the neutral directional overcurrent element to directionalize otherprotection elements.Figure 5–70: NEUTRAL DIRECTIONAL VOLTAGE-POLARIZED CHARACTERISTICS• NEUTRAL DIR OC1 POLARIZING: This setting selects the polarizing mode for the directional unit.– If “Voltage” polarizing is selected, the element uses the zero-sequence voltage angle for polarization. The usercan use either the zero-sequence voltage V_0 calculated from the phase voltages, or the zero-sequence voltagesupplied externally as the auxiliary voltage Vx, both from the NEUTRAL DIR OC1 SOURCE.The calculated V_0 can be used as polarizing voltage only if the voltage transformers are connected in Wye. Theauxiliary voltage can be used as the polarizing voltage provided SYSTEM SETUP Ö AC INPUTS ÖØ VOLTAGEBANK ÖØ AUXILIARY VT CONNECTION is set to “Vn” and the auxiliary voltage is connected to a zero-sequencevoltage source (such as open delta connected secondary of VTs).The zero-sequence (V_0) or auxiliary voltage (Vx), accordingly, must be higher than the PRODUCT SETUP ÖØDISPLAY PROPERTIES ÖØ VOLTAGE CUT-OFF LEVEL value to be validated for use as a polarizing signal. If thepolarizing signal is invalid, neither forward nor reverse indication is given.– If “Current” polarizing is selected, the element uses the ground current angle connected externally and configuredunder NEUTRAL OC1 SOURCE for polarization. The Ground CT must be connected between the ground and neutralpoint of an adequate local source of ground current. The ground current must be higher than 0.05 pu to be vali-dated as a polarizing signal. If the polarizing signal is not valid, neither forward nor reverse indication is given.For a choice of current polarizing, it is recommended that the polarizing signal be analyzed to ensure that a knowndirection is maintained irrespective of the fault location. For example, if using an autotransformer neutral currentas a polarizing source, it should be ensured that a reversal of the ground current does not occur for a high-sidefault. The low-side system impedance should be assumed minimal when checking for this condition. A similar sit-uation arises for a Wye/Delta/Wye transformer, where current in one transformer winding neutral may reversewhen faults on both sides of the transformer are considered.– If "Dual" polarizing is selected, the element performs both directional comparisons as described above. A givendirection is confirmed if either voltage or current comparators indicate so. If a conflicting (simultaneous forwardand reverse) indication occurs, the forward direction overrides the reverse direction.827805A1.CDRVAG(reference)VBGVCG–3I_0 line3I_0 lineECA line–ECA lineLALALALAECAFWD LAlineFWD OperatingRegionREV OperatingRegionFWD LAlineREV LAlineREV LAline–3V_0 line3V_0 line
