CHAPTER 4: SETPOINTS PROTECTION869 MOTOR PROTECTION SYSTEM – INSTRUCTION MANUAL 4–199REV 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 atleast 1.25 of a power system cycle, the prospective forward indication will be delayed by1.5 of a power system cycle. The element is designed to emulate an electromechanicaldirectional device. Larger operating and polarizing signals will result in faster directionaldiscrimination bringing more security to element operation.The forward-looking function is designed to be more secure as compared to the reverse-looking function, and should therefore be used for the tripping direction. The reverse-looking function is designed to be faster as compared to the forward-looking function andshould be used for the blocking direction. This allows better protection coordination.The above bias should be taken into account when using the Neutral DirectionalOvercurrent element to directionalize other protection elements.Figure 4-71: Neutral Directional Voltage-polarized CharacteristicsPath: Setpoints > Protection > Group 1(6) > Current > Neutral Directional OC 1(X)827805A1.CDRVAG(reference)VBGVCG-3I_0 line3I_0 lineECA line-ECA lineLALALALAECAFWD LAlineFWD OperatingRegionREV OperatingRegionFWD LAlineREV LAlineREV LAline-3V_0 line3V_0 line
