GE Multilin D60 Line Distance Relay 5-1895 SETTINGS 5.6 CONTROL ELEMENTS5d) VT FUSE FAILUREPATH: SETTINGS ÖØ CONTROL ELEMENTS ÖØ MONITORING ELEMENTS ÖØ VT FUSE FAILURE 1(4)Every signal source includes a fuse failure scheme.The VT fuse failure detector can be used to raise an alarm and/or block elements that may operate incorrectly for a full orpartial loss of AC potential caused by one or more blown fuses. Some elements that might be blocked (via the BLOCKinput) are distance, voltage restrained overcurrent, and directional current.There are two classes of fuse failure that may occur:Class A: Loss of one or two phases.Class B: Loss of all three phases.Different means of detection are required for each class. An indication of Class A failures is a significant level of negativesequence voltage, whereas an indication of Class B failures is when positive sequence current is present and there is aninsignificant amount of positive sequence voltage. These noted indications of fuse failure could also be present when faultsare present on the system, so a means of detecting faults and inhibiting fuse failure declarations during these events is pro-vided. Once the fuse failure condition is declared, it will be sealed-in until the cause that generated it disappears.An additional condition is introduced to inhibit a fuse failure declaration when the monitored circuit is de-energized; positivesequence voltage and current are both below threshold levels.The VT FUSE FAILURE 1(2) FUNCTION setting enables/disables the fuse failure feature for each source.Figure 5–111: VT FUSE FAIL SCHEME LOGIC VT FUSE FAILURE 1VT FUSE FAILURE 1FUNCTION: DisabledRange: Disabled, Enabled827093AH.CDRVT FUSE FAILUREFUNCTION:V_2 > 0.15 p.u.V_1 < 0.05 p.u.V_1 < 0.7 p.u.I_1 > 0.075 p.u.I_1 < 0.05 p.u.RUNRUNRUNRUNRUNSETTINGCOMPARATORSSOURCE 1FLEXLOGIC OPERANDSFLEXLOGIC OPERANDFLEXLOGIC OPERANDFLEXLOGIC OPERANDDisabled=0Enabled=1SRC1 VT FUSE FAIL OPSRC1 VT FUSE FAIL VOL LOSSSRC1 VT FUSE FAIL DPOFUSEFAILFAULTSRC1 50DD OPOPEN POLE OPD60, L60 onlyANDANDANDANDSETRESETReset-dominantLATCHANDANDANDANDANDORORORORV_1I_1V_220 CYCLES2 CYCLESLATCHSETReset-dominantRESET
