5-118L90 Line Differential RelayGE Power Management5.5 GROUPED ELEMENTS 5 SETTINGS55.5.21 SUPERVISING ELEMENTSPATH: SETTINGS Ø GROUPED ELEMENTS ÖØ SUPERVISING ELEMENTSa) DISTURBANCE DETECTORPATH: SETTINGS ÖØ GROUPED ELEMENTS ÖØ SUPERVISING ELEMENTS Ö DISTURBANCE DETECTORThe DD element is an 87L-dedicated sensitive current disturbance detector that is used to detect any disturbance on theprotected system. This detector is intended for such functions as; trip output supervision, VT and CT failure supervision,starting oscillography data capture, and providing a continuous monitor feature to the relays.If the disturbance detector is used to supervise the operation of the 87L function, it is recommended that the 87L TRIP logicelement be used. The 50DD SV disturbance detector FlexLogic™ output operand must then be assigned to an 87L TRIPSUPV setting.The DD function measures the magnitude of the negative sequence current (I_2), the magnitude of the zero sequence cur-rent (I_0), the change in negative sequence current (∆I_2), the change in zero sequence current (∆I_0), and the change inpositive sequence current (∆I_1).The DD element uses the same source of computing currents as that for the current differential scheme 87L.The Adaptive Level Detector operates as follows:• When the absolute level increases above 0.12 pu for I_0 or I_2, the Adaptive Level Detector output is active and thenext highest threshold level is increased 8 cycles later from 0.12 to 0.24 pu in steps of 0.02 pu. If the level exceeds0.24 pu, the current Adaptive Level Detector setting remains at 0.24 pu and the output remains active (as well as theDD output) when the measured value remains above the current setting.• When the absolute level is decreasing from in range from 0.24 to 0.12 pu, the lower level is set every 8 cycles withoutthe Adaptive Level Detector active. Note that the 50DD output remains inactive during this change as long as the deltachange is less than 0.04 pu.The Delta Level Detectors (∆I) detectors are designed to pickup for the 0.04 pu change in I_1, I_2, and I_0 currents. The ∆Iis measured by comparing the present value to the value calculated 4 cycles earlier.DD FUNCTION:This setting is used to Enable/Disable the operation of the Disturbance Detector.DD NON-CURRENT SUPV:This setting is used to select a FlexLogic™ operand which will activate the output of the Disturbance Detector upon events(such as frequency or voltage change) not accompanied by a current change. SUPERVISING ELEMENTS DISTURBANCE DETECTORMESSAGE OPEN POLE DETECTORMESSAGE 87L TRIP DISTURBANCE DETECTORDDFUNCTION: DisabledRange: Disabled, EnabledMESSAGE DD NON-CURRENT SUPV:OffRange: FlexLogic™ operandMESSAGE DD CONTROL LOGIC:OffRange: FlexLogic™ operandMESSAGE DD LOGIC SEAL-IN:OffRange: FlexLogic™ operandMESSAGE DDEVENTS: DisabledRange: Disabled, Enabled
