5-292 D60 Line Distance Protection System GE Multilin5.7 CONTROL ELEMENTS 5 SETTINGS5e) VT FUSE FAILUREPATH: SETTINGS CONTROL ELEMENTS MONITORING ELEMENTS 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 BLOCK input)are distance, voltage restrained overcurrent, and directional current.There are two classes of fuse failure that 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 negative-sequence voltage, whereas an indication of class B failures is when positive sequence current is present and there is aninsignificant amount of positive sequence voltage. Also rapid decrease in the phase voltages magnitude from a healthyvoltage level without disturbance in current can indicate a VT fuse fail conditions. These noted indications of fuse failurecan also be present when faults are present on the system, so a means of detecting faults and inhibiting fuse failure decla-rations during these events is provided.Once the fuse failure condition is declared, it is 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; positive-sequence voltage and current are both below threshold levels.The VT FUSE FAILURE 1 FUNCTION setting enables and disables the fuse failure feature for each source.The VT NEU WIRE OPEN 1 FUNCTION setting enables and disables the VT neutral wire open detection function. When theVT is connected in Delta, do not enabled this function because there is no neutral wire for Delta connected VT.The VT NEU WIRE OPEN 1 3 HRAM PKP setting specifies the pickup level of 3rd harmonic of 3V0 signal for the VT NEUWIRE OPEN detection logic to pick up. VT FUSE FAILURE 1VT FUSE FAILURE 1FUNCTION: DisabledRange: Disabled, EnabledMESSAGE NEUTRAL WIRE OPEN 1 DETECTION: DisabledRange: Disabled, EnabledMESSAGE NEUTRAL WIRE OPEN 1 3 HARM PKP: 0.1000.000 to 3.000 pu in steps of 0.001
