GE Multilin F60 Feeder Protection System 5-2095 Z SETTINGS 5.7 CONTROL ELEMENTS5The number of detected incipient faults in each phase is counted and available in the ACTUAL VALUES Ö STATUS ÖØ INCIPI-ENT FAULT menus. The counters can be reset with the COMMANDS ÖØ CLEAR RECORDS ÖØ CLEAR INCIPENT FAULT COUN-TERS command.Changes to any of the incipient cable fault detector settings resets of the number of the incipient faults detected tozero.To provide a clear timing indication when the incipient fault occurred, the incipient fault event is time-stamped withthe time the fault actually occurred. However, the FlexLogic™ operand is asserted four cycles later, when the incip-ient fault pattern is confirmed and therefore detected.The following figure illustrates a recorded field case of an incipient phase B fault. The top portion of the figure shows theraw A, B and C currents. The bottom portion shows the neutral current (blue) and reveals the fault period from under theload and the superimposed phase B current (red). The superimposed current shows two fault current blips as the dataslides through the two-cycle memory window. During the actual fault, the neutral current and the superimposed phase Bcurrents closely correspond, confirming the incipient fault hypothesis and identifying the affected phase.Figure 5–108: ILLUSTRATION OF THE INCIPIENT FAULT DETECTOR ALGORITHMThe following settings are available for each incipient cable fault detector.• INCIPIENT FAULT 1 FUNCTION: This setting enable and disables operation of the incipient fault detection element.• INCIPNT FLT 1 BLOCK: This setting is used to block operation of the incipient cable fault detector element. Assertionof the FlexLogic™ operand assigned to this setting block operation.• INCIPIENT FAULT 1 SOURCE: This setting selects a current source for the incipient cable fault detector element. Thissource must be assigned a valid CT bank.• INCIPIENT FAULT 1 PICKUP: This setting specifies pickup level of the overcurrent detector in per-unit values of theCT nominal current.• INCIPNT FLT 1 MODE: There are two modes of operation available for the incipient cable fault detector element. Inthe “Number of counts” mode, a trip will be initiated only after the selected number of faults is detected. In the “Countsper window” mode, a trip will be initiated only after the selected number of faults is detected within the time specified bythe INCIPNT FLT 1 DETECT WINDOW setting.• INCIPIENT FLT 1 TRIP COUNTS NUMBER: This setting selects the number of faults required to initiate a trip.• INCIPNT FLT 1 DETECT WINDOW: This setting specifies a time window for “Counts per window” mode of operation.NOTENOTE0.62 0.64 0.66 0.68 0.70 0.72 0.7401.02.00.62 0.64 0.66 0.68 0.7 0.72 0.74–2.0–1.001.02.0 IN (neutral current)IFB–0.5 Phase BPhase CPhase AIncipient phase B faultCurrent (amps)Current (amps)832774A1.CDRPHASE CURRENTSCALCULATED NEUTRAL ANDSUPERIMPOSED PHASE B CURRENT
